Electro-Motor Cruise System - 73
Contents
1. 18 AC Electro Motor Cruise System Service Manual Schematic Symbol Explanation S3A ISPLICE 39C 8 PNK BLK ENTIRE Q sam 20 AMP FUSE COMPONENT 4 4 BLOCK SHOWN 1 caces 1 FUSE PART OF A COMPONFNT ss oe SHOWN HOT IN RUN SPEED SENSOR AT TRANSMISSION SPEED INPUTS paeem am mr mr m an p UM Sur sr asr ARE 437A 8 BRNIWHT A18 INSTRUMENT GJ CRUISE SPEED CLUSTER SIGNAL OUTPUT GROUND TERMINAL asa B BLE ANH 450 B BLKIWHT san 39 8 PNK BLK CONNECTOR ATTACHED TO COMPONENT 401 BY 400 BY 8 PPL 8 YEL E TERMINAL BULKHEAD CONNECTOR IN _ _ 401 400 caa am 8 PPL 8 YEL i 816 aia UR INSULATION COLOR IS LABFI FD SPLICES ARE SHOWN AND NUMBERED CIRCUIT NUMBER 18 SHOWN TO HELP IN TRACING CIRCUITS LINE MEANS WIRE 16 BE CONTINUED INDICATFS THAT THE CIRCUITRY IS 43 ast aRN WHTY 8 8LK WHT i 814 4 250 SHOWN IN 450 C 8 BLK WHT 8 COMPLETE DETAIL W BRN WHT rpm BUT 5 COMPLETE DISTRIBUTION IN DIVISION E SERVICE MANUAL ENGINF W s SPLICE t 15 i BLOCK GROUND 4 1 I SEE GROUND AMP WIRF CHOICES m m DJSTRIBUTION i FOR OPTIONS i SPEEDO MANUAL fa AUTOMATIC DIFF RENT 450 B BLK WHT FUSE ducet MOBFLS ARE SHOWN AND 1 LABELED a BULKHEAD 1 8 8 BAN CONNE2. 27 General Description of Electro Motor Cruise System The Electro Motor Cruise Control is speed control system which maintains a desired vehicle speed under normal driving conditions The Electro Motor Cruise Control System has the capability to CRUISE COAST RESUME SPEED ACCELERATE TAP UP and TAP DOWN The main parts of the cruise control system are the mode control switches cruise control module electri cal release switches electrical harness and cruise control cable The cruise control system uses a cruise control module to obtain the desired vehicle cruise operation see Figure 1 1 Two important components in the module help to do this One is an electronic controller and the second is an electric motor The controller monitors vehicle speed and operates the electric motor The Figure 1 1 Cruise Control Module AC Electro Motor Cruise System Service Manual motor in response to the controller moves a connecting strap and throttle linkage to maintain the desired cruise speed The cruise control module contains a low speed limit which will prevent system engagement below a minimum speed about 25 MPH The operation of the cruise module is controlled by mode control switches located on the turn signal lever Electrical release switches are provided to disengage the cruise system Two 2 release switches are mounted on the brake pedal bracket and one 1 switch is attached to the clutch pedal bracket on ve
3. of the cruise control module When the slider switch is moved to the ON position battery voltage is applied to terminal of the cruise control module connector If the brake and or clutch pedal is not depressed battery voltage is present at module terminal D When the slider switch is moved to the R A position battery voltage is applied to terminal of the module With the SET push button depressed battery voltage is pres ent at cruise module terminal Cruise module con nector terminal is the speed signal terminal In operation voltage will oscillate between a high of 4 to 5 volts and a low of near ground Cruise module termi nals H and J are not used Ground is at module terminal See GMT 400 Cruise Diagnostic Chart for reference to Figures 5 2 amp 5 3 pages 16 amp 17 Figure 5 2 Voltmeter Hookup Figure 5 3 Cruise Mode Switch Connector 15 400 Cruise Diagnostic Chart ICRUISE SYSTEM TROUBLESHOOTING WITH A HIGH IMPEDANCE DIGITAL VOLTMETERI TROUBLESHOOTING HINTS Checks for Ignition off Disconnect connector C4A from cruise module See circuit schematic page 18 ignition on Measure voltage at terminal F of C4A to a good ground 12 VOLTS 1 Cruise fuse labeled Gages in fuse block is OK if seat belt buzzer is working 2 Speedo fuse is OK if speedometer or odometer is operating 3
4. 12 VOLTS STEP 8 THINGS TO CHECK TO STEPS Start engine Move cruise slider switch to OFF Move cruise switch to and then wait at least 3 seconds before doing next step e Fully depress and hold brake pedal ENGINE RPM INCREASE CRUISE MODULE 3 OK THINGS TO CHECK Problem is intermittent Check connectors and wire terminals for contaminants toil grease dirt and for proper contact Also check ground terminals for con taminants and proper contact see ground check below Push cruise SET push button in and hold Hold cruise sider switch in RA position After 10 seconds release brake pedal while still holding and SET switches and listen for momentary engine RPM increase NO ENGINE RPM INCREASE THINGS TO CHECK 1 Check that cruise mod ule linkage is connected and operating freely 2 Check linkage adjust ment See pages 26 27 Check terminals in con nectors C3A C5A for contaminants oil grease dirt and for proper contact see ground check below e t OK replace cruise control module GOOD GROUND CHECK Turn ignition on move cruise slider switch to position Perform voltage check between suspected bad cruise ground and engine block Any voltage means ground is bad If step fails to locate problem run a second ground wire from engine block to pin
5. Check Convenience Center connector an open in cruise power circuit NOTES 1 Never attempt to back probe a sealed connector 2 Never attempt to insert meter leads into terminal slots 0 VOLTS Checks for resistance of cruise syst With ohmmeter measure resistance of BLK WHT wire 4501 from terminal E of C4A to engine black ground stud See circuit schematic em ground wire THINGS TO CHECK 1 Check Gages fuse 2 Check PNK wires 39A 398 and PNK BLK wires 39 39C for open See circuit schematic 3 Check connector C54 at Convenience Center for contaminants oil grease dirt and for and Cruise Module connector 4 for proper Connection see Figures 4 8 4 9 4 Check that cruise module linkage is connected and maving freely 5 Check cruise cable adjustment see page 26 Checks for a short in cruise control lever THINGS TO CHECK 1 Disconnect connector C3A Measure voltage again at terminals A B C and D of connector C4A f all terminals read zero volts replace cruise control lever If one or more Measure voltage at terminals B and C of to ground with cruise slider switch ON and ignition Switch on 12 VOLTS 0 VOLTS ATBAND C ATBORC terminals read 12 volts problem is in REPLACE CRUISE CONTROL LEVER Checks for an open in BRAKE circuit or ON OFF circuit Measure voltage at terminals
6. review task four Re form the locking tang Inspection Notes 23 Cruise Control Cable Installation and Adjustment Procedures AC Electro Motor Cruise System Service Manual Cable Installation Step 1 Attach cable bead to cruise module strap end fitting and remove retainer Figure 7 1 Step 2 A Pull cruise cable engine end fitting until cable is snug Figure 7 2 B Turn cruise cable strap end fitting to straighten strap Strap should be flat and vertical Note Strap must not be twisted as shown in Figure 7 2 Step 3 Slide cable conduit over strap and install tangs in cruise motor housing Figure 7 3 24 Figure 7 1 Cable Installation Figure 7 2 Cable Installation Figure 7 3 Cable Installation n J EO AC Electro Motor Cruise System Service Manual Step 4 Install cable conduit in engine bracket Figure 7 4 Step 5 A Unlock cable conduit Figure 7 5A B Attach cable engine end fitting to lever stud and install retainer clip Figures 7 5B 7 7 Step 6 Lock cable conduit by pushing down firmly on lock until it locks in place Figure 7 6 Figure 7 4 Cable Installation Figure 7 5 Cable Installation Figure 7 5B Cable Installation Figure 7 6 Cable Installation Cruise Control Cable Installation and Adjustment Procedures AC Electro Motor Cruise System Service Manual Cable Adjustme
7. A and D of C4A to ground with cruise slider switch ON and ignition switch on 12 VOLTS 0 VOLTS 0 VOLTS 0 VOLTS AT A AND D AT A ANDD ONLY ATD ONLY AT A THINGS TO CHECK 0 VOLTS AT A AND D 1 Check for 12 volts at terminal A of female half of connector C3A f zero volts check and B of male half of with cruise switch ON See Figure 5 3 f open replace cruise control lever proper contact RESISTANCE RESISTANCE LESS THAN 1 OHM GREATER THAN 1 OHM Checks for a short in cruise wiring harnass Measure voltage at THINGS TO CHECK 16 terminals B C and D of C4A to ground with cruise slider switch OFF and ignition on 0 VOLTS AT ALL TERMINALS 1 Check engine block ground stud for a clean and tight connection 2 Check condition of wire 450 from terminal E of C4A to engine block ground stud 12 VOLTS AT ONE OR MORE TERMINALS TO STEP 4 for open in PNK wire 39 3 Check for open in GRA 2 Check continuity wire 39781 between terminals 0 VOLTS ONLY 1 Check for open or mis 2 Check for open in adjusted brake switches brake clutch switch or clutch switch winng from splice S2A to terminal D or i0 VOLTS ONLY AT A 1 Check for an open in GRA wire 397A TO STEP 6 Checks for an open in SET COAST circuit STEP 8 THINGS TO CHECK 12 VOLTS 1 Check for short to ground on BRNAWHT wires 437 437A Ignitio
8. Plug Division has designed and manufactured since the 1977 vehicle model year The EMCS has been engineered to function as an all electric system Like Custom Cruise III the Electro Motor Cruise System places at the driver s fingertips the cruise control functions of CRUISE COAST RESUME TAP UP TAP DOWN and Each function is controlled by either the slider switch or the push button on the turn signal lever The EMCS makes use of an electric motor and connecting strap to vary the throttle angle As a result the motor actuated throttle linkage affords a mode of operation that is completely vacuum independent and consistently gives smoother throttle control under changing driving conditions Electro Motor Cruise System also offers serviceability benefits EMCS has less than half the system parts of the Custom Cruise system B Major cruise components are reduced from four 4 to two 2 C No vacuum harnesses with difficult to locate leaks are needed D Built in diagnostics provide a check of the cruise system operation This service manual is intended to be a quick easy to use reference for servicing the Electro Motor Cruise System It has been organized into seven major sections General Description of Electro Motor Cruise System How to Use the Electro Motor Cruise System Components in the Electro Motor Cruise System GMT 400 Electro Motor Cruise System Block Diagram and System Layout GMT 400 GMT 4
9. shown Attach terminal to tool and pull wire through column until slack is removed Figure 7 8 Step 5 Slide cruise control wire protector over Figure 7 8 Cable Adjustment wire from lever Then slide protector over nib on main wire protector until lower end is even with lower end of main protector Figure 7 9 Figure 7 9 Cable Adjustment AC Electro Motor Cruise System Service Manual Inspaction Notes 28 AC Spark Plug Division General Motors Corporation 1300 N Dort Highway Flint Michigan 48556 U S A Austral a AC Spark Plug Overseas Corporation 499 St Kilda Road 15th Floor Melbourne 3004 Victoria Ausualia France AC Spark Plug General Motors France 58 68 Avenue Louis Roche 92231 Gennevilliers France Japan AC Spark Plug Asia Pacific Region GMOC Tokyo Zane Roppongi Fuji Building Sth Floor 2 6 Nishiazabu 3 Chome Minato ku Tokyo 105 Japan England AC Spark Plug Overseas Corporation P O Box 336 Sentry House 500 Avebury Blvd Central Milton Keynes Milton Keynas MKS 2NH England Italy AC Spark Pluq General Motors talis S p A Via S Quintino 28 Pala220 Galileo 1 10121 Torino Italy Germany AC Spark Pluq General Motors Service GmbH isenstrasse 2 Postfach 1507 D 8080 Russelsheim Federal Republic of Germany nasi F zw ANN rr A esse AE ELMO TENIENDO a a A10022 Litho in US A 4 87
10. 00 Cruise Diagnosis and Troubleshooting Connector Disassembly and Repair Cruise Control Cable Installation and Adjustment Procedures SOS UNES Contents AC Electro Motor Cruise System Service Manual IT TL rd General Description of Electro Motor Cruise 3 How to Use the Electro Motor Cruise System ee hr 4 Components in the System GMT 400 ROL Y e t Cn 6 Electro Motor Cruise Block Diagram and System Layout 400 8 GMT 400 Cruise Diagnosis and Troubleshooting 212 Connector Disassembly and zu av Cruise Control Cable Installation and Adjustment Procedures 24 Iilustrations Cruise Control Module 3 2 Wheel Drive Speed Sensor Location Mode Control Switches on Turn Signal Lever 4 TANSMISSIQNE eee eie eu 11 Internal Transmission Speed Sensor 6 Chart Road Test of Cruise System 14 Combination Cruise Stop Voltmeter HooKUD 15 Converter Clutch 6 Cruise Mode Switch Connector 15 Plunger Type Cruise Release Switch 7 GMT 400 Cruise Diagnostic 16 Cruise Control Module 7 Electro Motor C
11. 4 volt AC peak 2 volts AC RMS at 2 MPH to 100 volts 70 volts AC RMS AC peak at maxi mum speed This signal is sent to the vehicle s instru ment cluster which contains the vehicle speed cir cuitry Integrated Vehicle Speed Circuitry The vehicle speed information from the Internal Trans mission Speed Sensor is transmitted to the vehicle speed circuitry The speed circuitry electronics have been built into the instrument cluster The speed circuitry consists of solid state electronic components that condition and process the speed sig nal The signal is converted to a square wave of 1112 Hertz MPH which is needed by the cruise control mod ule The output frequency is proportional to vehicle speed Electric Brake Release Switches The combination CRUISE STOP LIGHT CONVERTER CLUTCH switch is used in series with a separately mounted plunger type cruise release switch see Figures 3 2A 3 2B When the brake pedal is depressed each switch disengages the cruise control system The cruise function remains disengaged after the brake pedal is released Figure 3 1 Internal Transmission Speed Sensor Figure 3 2A Combination Cruise Stop Light Converter Clutch Switch AC Electro Motor Cruise System Service Manuai Figure 3 4 Cruise Controi Module Electric Clutch Release Switch On vehicles with manual trensmission a plunger type clutch switch see Figure 3 2B is used in series with the two 2 brake switches When
12. CTOR l 1 I 1 ENGINE BLOCK SEE GROUND DISTRIBUTION IN OIVISION SERVICE MANUAL l B Y gt l HOT IN RUN sa CONVENIENCE CENTER Twa QR MORE TERMINALS IN THE CONNECTOR ANDY DASHED LINE SHOWS SHYSICAL CONNECTION BETWEEN PARTS ISAME CONNECTOR 19 Connector Disassembly and Repair AC Electro Motor Cruise System Service Manual Cruise Control Module Metri Pack Connector Metri Pack or weatherproof connectors provide environmental protection for the electrical circuits This protection consists of a moisture proof rubber seal between the two connector halves and rubber cable seals attached to each terminal The terminals and the cable seals are secured by a plastic terminal retainer Note NEVER ATTEMPT TO BACK PROBE SEALED CONNECTORS Metri Pack connector requires repair do not replace the Metri Pack parts with other types of connectors and terminals Also do not omit either the large seal or the cable seals when making a repair Instruction in the disassembly repair and assembly of the Metri Pack connector follows Only perform those tasks necessary to make the repair TASK ONE Removal of connector from Cruise Control Module To remove the connector use your finger to pull up and outward on the connector s locking tab Not much pull is required for removal see Figure 5 1 Figure 6 1 Cruise Module Connector Removal NOTE To lessen repai
13. a AC A Electro Motor Cruise System Service Manual IMPORTANT SAFETY NOTICE To reduce the chance of personal injury and or property damage the following instructions must be carefully observed Proper service and repair are important to the safety of the service technician and the safe reliable operation of all motor vehicles If part replacement is necessary the part must be replaced with one of the same part number or with an equivalent part Do not use a replacement part of lesser quality The service procedures recommended and described in this service manual are effective methods of performing service and repair Some of these procedures require the use of tools specially designed for the purpose Accordingly anyone who intends to use a replacement part service procedure or tool which is not recommended by the vehicle manufacturer must first determine that neither his safety or safe operation of the vehicle will be jeopardized by the replacement part service procedure or tool selected It is important to note that this manual contains various cautions and notices that must be carefully observed in order to reduce the risk of personal injury during service or repair or the possibility that improper service or repair may damage the vehicle or render it unsafe It is also important to understand that these cautions and are not exhaustive because it is impossible to warn of all the possible h
14. azardous consequences that might result from failure to follow these instructions r B G H EVR 0 LET Central Office TO ALL CHEVROLET DEALERS SUBJECT AC ELECTRO MOTOR CRUISE SYSTEM SERVICE MANUAL Enclosed is a Service Manual for the new AC Electro Motor Cruise System that is utilized on 1988 Chevrolet C K Trucks This service manual is intended to be a quick easy to use reference for servicing the Electro Motor Cruise System Chevrolet is offering a training program concerning this new cruise control system plus other electrical components used on the 1988 C K Truck through General Motors Training Centers and remote training locations The course number is 10488 01 1988 C K Truck Electrical Electronics Program and is 1 day in length We encourage attendance by your electrical technicians We recommend that the enclosed service manual be reviewed by your service manager and electrical technicians A R W Starr General Sales amp Service Manager Chevrolet Motor Division Generat Motors Corporation 30007 Van Dyke Avenue Warren Michigan 48090 Foreword AC Electro Motor Cruise System Service Manual Spark Plug Division of General Motors Corporation has prepared this service manual to help answer questions about the operation and service of the AC Electro Motor Cruise System EMCS The AC Electro Motor Cruise System is an extension of the electronic cruise control systems that AC Spark
15. ctional Check The procedure below is used to check the operating modes of the cruise control system This procedure should always be used after repair work has been com pleted on the cruise system Steps 1 7 and 10 are used with automatic and manual transmission vehicles while steps 8 and 9 are for manual transmission only ROAD TEST PROCEDURE Slide the turn signal lever cruise switch to the position Check the Low Speed Inhibit Drive vehicle at 20 MPH Depress SET push button and release Cruise control must not engage Check Set Speed Drive vehicle at steady speed of 55 MPH Depress SET push button completely and release Cruise control should engage at approxi mately 55 MPH Check Brake Release Depress brake pedal The cruise control must release throttle allowing the vehicle speed to drop The system must not re engage when the brake is released Check Resume Feature With the vehicle speed at approximately 45 MPH slide the cruise switch momentarily less than 1 second to the R A position The vehicle should accelerate to approximately 55 MPH Check Coast Feature Depress the SET push button and hold Allow the vehicle speed to drop to 50 MPH and release push button Cruise control should hold vehicle speed at approximately 50 MPH Check Accelerate Feature Slide the cruise switch to the R A position and hold The vehicle speed should begin to increase Allow the speed to incr
16. d circuitry Figure 4 1 Block Diagram Electro Motor Cruise System Electro Motor Cruise System Service Manual Engine Compartment Cruise Configurations Figure 4 2 Installation on LB4 4 3L LO3 15 01 LOS 5 7L Figure 4 3 Installation on LH6 amp LL4 6 2L Diesel Figure 4 4 Installation on L19 7 4L Electro Motor Cruise Block Diagram and System Layout GMT 400 AC Electro Motor Cruise System Service Manual Component Location Views Figure 4 5 Cruise Mode Switch Location Steering Column Figure 4 6 Clutch Release Switch Location Behind Instrument Panel Figure 4 7 Brake Release Redundant Release Switch Figure 4 8 Cruise Module Location Engine Compartment Location Behind Instrument Panel Bulkhead 10 Figure 4 9 Wiring Harness Location Behind Instrument Panel on Left Figure 4 10 Convenience Center Location Behind Instrument Panel Figure 4 11 AC Electro Motor Cruise System Service Manual Speed Sensor 2 Wheel Drive Speed Sensor Location Transmission Note 4 Wheel Sensor on Transfer Case 11 GMT 400 Cruise Diagnosis and Troubleshooting AC Electro Motor Cruise System Service Manual Preliminary Diagnosis and Inspection When a vehicle is brought in with a cruise performance complaint it is important to carry out a preliminary diagnosis Thus diagnosis should be used to determine whether the cruise complaint is the result of an actual Cru
17. e disengaged by moving the slider switch to the position or by depressing the brake pedal or clutch pedal on manual transmission vehicles A momentary slider switch movement from the ON position to R A will also operate as a SET mode function if the previous cruise speed has been cleared from the module s mem ory Memory is cleared by moving the slider switch to OFF or by turning the ignition switch to OFF The accelerator pedal may be depressed at any time to override the cruise system Release of the accelerator will return the vehicle to the SET cruise speed Coast To decrease cruise speed the SET push button switch is held in the depressed position In the depressed position the vehicle cruise system is disen gaged and the throttle is returned to the idle position When the vehicle has slowed or COASTED to the desired speed releasing the switch will re engage the system and SET the new cruise speed AC Electro Motor Cruise System Service Manual Resume If the cruise control system is disengaged by depress ing the brake or clutch pedal the vehicle can be returned to the last speed stored in memory by momentarily holding the slider switch in the position for less than 7 0 second The vehicle will automatically accelerate at a controlled rate Holding the slider in the R A position for more than 1 0 second causes the cruise system to go
18. ease to 55 MPH and release switch The cruise control should hold the vehicle at approximately 55 MPH ITEMS 8 AND 9 ARE FOR MANUAL TRANSMISSION ONLY Check Clutch Release Depress clutch The cruise control must release throttle allowing the vehicle speed to drop The system must not re engage when the clutch is released Slide the cruise switch to the R A position momentarily to resume to 55 MPH Check Off Switch Turn the cruise control switch to the OFF position This must disengage the cruise control system Figure 5 1 Chart Road Test of Cruise System 14 System Diagnosis The troubleshooting chart on page 16 provides an organized approach for locating a problem in the cruise system Understanding the chart and using it correctly will reduce diagnosis time and prevent unnecessary replacement of parts HOW TO USE CHART Disconnect the cruise control module connector see Figure 6 1 page 20 Task One and perform the troubleshooting steps at the connector A high imped ance digital voltmeter is used to make the checks f theresults of the test step are not cor rect go to THINGS TO CHECK box for that test step If the results of a test step are correct go to next step AC Electro Motor Cruise System Service Manual Circuit Operation With the IGNITION SWITCH in RUN see circuit schematic page 18 battery voltage is applied through the GAGES FUSE to terminal
19. gure 6 4 Also check to see that the remainder of the terminal is still in its original shape TASK FIVE the repair Figure 6 4 Re forming Locking Tang When making a repair use the correct types of terminals wires and seals C Step 1 Cut the wire immediately behind the cable seal Step 2 Slip the new cable seal onto the wire and push it back out of the way Step 3 Strip 5 0 mm 2 inches of insulation from the wire Step 4 Crimp the new terminal over the wire core crimp as shown in Figure 6 5 Step 5 Solder with rosin core solder Step 6 Move the cable seal to edge of the insulation Step 7 Crimp the grips at the end of the termi nal around the cable seal and insulated wire as shown in Figure 6 5 Apply slight pressure for this crimp For splicing wires follow the directions given in the Division Service Manual Figure 6 5 Connector C4A Terminal 22 AC Electro Motor Cruise System Service Manual TASK SIX Insert the lead TASK Replace the terminal retainer Before inserting the lead make certain that the termi Replace the terminal retainer by firmly pushing on the nal is correctly shaped Then gently insert the lead retainer until both locks snap into place from the back The terminal should stop or catch about halfway through the connector body Gently push back and forth on the lead to be sure the terminal is held in place in both directions If the terminal easily pushes or pulls out
20. hicles with manual transmission When the brake pedal or clutch pedal is depressed the cruise system is electrically disengaged and the throttle is returned to the idle position How to Use the Electro Motor Cruise System AC Electro Motor Cruise System Service Manual Operation of Mode Control Switches The various operating modes of the Electro Motor Cruise System EMCS are controlled by mode control switches located on the turn signal lever see Figure 241 Following is a description of how the different functions are initiated by either the push button or the slider switch Figure 2 1 Mode Control Switches on Turn Signal Lever 3 NOTE The cruise mode functions of SET COAST RESUME ACCEL R A ACCELERATION ACCEL TAP UP and TAP DOWN are inoperative when vehicle speed is less than 25 MPH This is a low speed inhibit feature Modes and Procedures Movement of slider switch to the position allows engagement of the cruise system Movement of slider switch to the OFF position releases throttle clears cruise memory speed and puts the vehicle in a non cruise mode Set The cruise system is engaged by depressing the SET push button and then releasing it slider switch must be in the ON position The cruise speed will be the vehicle speed at the time the push button is released This speed is stored in the cruise module s memory The cruise system may b
21. into the acceleration ACCEL mode The vehicle operator may interpret this as a faulty RESUME function Acceleration ACCEL if the slider is moved to the R A position and held the vehicle will accelerate at a controlled rate until the slider is released When the slider is released the vehi cle will continue to cruise at that speed The accelera tion function can be operated in either the cruise or non cruise mode Tap Down While in cruise momentarily depressing the SET push button less than 3 8 seconds decreases vehicle speed by one 1 MPH Tap Up While in cruise momentarily moving the slider switch less than 3 4 seconds to the R A position increases vehicle speed by one 1 MPH Cancel Depressing both the SET push button and the R A slider switch at the same time releases the throttle and puts the vehicle in a non cruise mode The cruise module s memory speed is not changed Components in the System GMT 400 AC Electro Motor Cruise System Service Manual Component Functions Mode Control Switches The various operating modes of the Electro Motor Cruise System are controlled by means of mode switches located on the turn signal lever see Figure 2 1 internal Transmission Speed Sensor ITSS The transmission speed sensor see Figure 3 1 gener ates vehicle speed information in the form of a high frequency sine wave The voltage output ranges from one fourth 1
22. ise system defect or the result of a problem with some other vehicle system or component Also some cruise complaints may be a misunderstand ing by the driver about how the cruise system func tions In that case the operation of the cruise system should be explained in a manner that the customer understands A practical demonstration is very useful especially with a similar vehicle which has the same cruise control system If it is decided the cruise system is at fault perform a visual inspection of all components in the cruise sys tem Cruise performance can be mechanical electrical or combination of the two Things to check are Dirty corroded or loose ground terminals Damaged or mispositioned brake and or clutch switches Binding or sticking linkage at the throttle body Damaged components Bare broken or disconnected wires Adjustment of cruise control module linkage see Cable Adjustment Check page 26 If preliminary inspection reveals no solution and the system is malfunctioning follow the system diagnostic chart to isolate the problem see page 16 GOOD ADVICE Verify the problem before you attempt any repairs Sometimes normal operating characteristics may be misunderstood as a problem 12 Inspection Notes AC Electro Motor Cruise System Service Manual 13 GMT 400 Cruise Diagnosis and Troubleshooting AC Electro Motor Cruise System Service Manual Cruise System Fun
23. n on Push cruise SET push Move cruise slider Switch to ON button in and hold 0 VOLTS Measure voltage at 1 Check Speedo fuse 2 Check for open on BRN WHT wires 437 437A terminal B of C4A to ground wires are OK see electrical section of Division Service Manual for additional speed sensor diagnostics 12 VOLTS 0 VOLTS Checks for operation of Checks for an open in contre module RESUME ACCEL IR circuit Hold cruise slider switch in RIA position Measure voltage at terminal C of C4A to ground THINGS TO CHECK 1 Disconnect connector and check tinuity between termi nals B and D of male half with SET push button depressed See Figure 5 3 12 VOLTS Chacks for an open or short in vehicle speed circuit Put voltmeter on DC voltage scale Connect voltmeter across pins F and K of connector C4A See Figure 5 2 gnition on raise vehicle put transmission in neutral Spin drive wheels by hand VOLTAGE VARYING BETWEEN 0 AND 12 VOLTS 0 VOLTS RECONNECT CRUISE MODULE CONNECTOR C4A e open replace Cruise control lever 2 Check for open in DK BLU wire 841 0 VOLTS THINGS TO CHECK Disconnect and Check continuity between terminals and C of male half with cruise switch in position f open replace cruise control lever Check for open in DK wire 83
24. nt Check Step 1 Disconnect cruise cable engine end from lever stud Figures 7 5 7 7 Step 2 Pull lightly on cable end Step 3 If cable end does not extend forward adjustment is OK if cable end does extend forward per form steps in Cable Adjustment Cable Adjustment Step 1 Reconnect cable to lever stud Figures Figure 7 7 Cable Adjustment Step 2 Unlock cable conduit engine fitting Fig ure 7 5 Step 3 For gasoline TBI engines turn ignition off Move cable conduit see Cable Con duit Figure 7 4 until throttle plate begins to open Then move conduit in opposite direction enough to return throt tle plate to closed position For diesel engines turn ignition off Move cable conduit until injector purnp lever moves from idle stop screw Then move conduit in opposite direction enough to return lever to idle stop screw Figure C 7 7 Step 4 While holding cable conduit push down firmly on cable conduit lock until it locks in place Figure 7 6 NOTE DO NOT RELEASE HAND GRIP FROM CABLE CONDUIT UNTIL STEP 4 IS FINISHED 26 AC Electro Motor Cruise System Service Manual Cruise Control Mode Switch Turn Signal Lever Installation Step 1 Rotate 107107 position Step 2 Put turn signal switch in right turn position Step 3 For tilt column installation column is to be in full up position Step 4 Insert music wire tool into opening and route through column as
25. of cruise module If second wire corrects problem then recheck ground path 450 for problem Remove second wire after troubleshooting is completed 17 400 Cruise Diagnosis and Troubleshooting AC Electro Motor Cruise System Service Manual Electro Motor Cruise System Circuit Schematic 39A 8 PNK S1A SPLICE Y nu Any SON s ADV s 4 CRUISE SWITCH 39A ss B PNK BLK RESUME 8 PNK ON ACCEL SET SWITCH SWITCH RED VEL VO C3A CONNECTOR d 52 SPLICE lt 3978 B GRA Y amar GERE Gr amar p asp CRUISE 397 GRA 1 397 A RELEASE 8 GRA SWITCH OPEN WITH BRAKE PEDAL IGN IGN DEPRESSED OUTPUT INPUT 900 8 LT GRN 397 84 CONVENIENCE B GRA B DK BLU CENTER SIGNAL CRUISE BRAKE SWITCH GROUND GROUND OPEN WITH OUTPUT INPUT BRAKE PEDAL DEPRESSED MANUAL AAUTOMATIC O o p oaase Yesa H 83 ORANGE Q X dm Y 87 8 8 DK ORN j CONNECTOR CLUTCH 1 SWITCH 86 A 450 WITH 8 BRN 37 8 BRN WHT BLKWHT CLUTCH PEDAL Y w w w w DEPRESSED l 8 BRN L B c K E C4A CONNECTOR m am m a a am a me ers BRAKE ON OFF SET COAST RESUME ACCEL VEHICLE GROUND INPUT INPUT INPUT INPUT SPEED INPUT CRUISE CONTROL MODULE
26. r work time use terminal pick tool Kent Moore P N J 35689 A Burroughs P N BT 8446 or equivalent 20 AC Electro Motor Cruise System Service Manual TASK TWO Remove the terminal retainer To remove the terminal retainer position a wide pick or small screwdriver at a 45 angle between the connec tor body and terminal retainer and then exert enough force to slip terminal retainer over the locking nib Do this with both locking nibs see Figure 5 2 TASK THREE Remove the lead Depress the terminal locking tang using a Metri Pack Terminal pick tool Step 1 Push the metal pick into the narrow por tion of the terminal cavity from the front until it stops The pick should be placed between the locking tang of the terminal and the plastic of the connector body see Figure 6 3 Figure 6 2 Connector C4A Retainer Removal Step 2 Pull the pick out Step 3 Gently pull the lead out of the back of the connector body NEVER USE FORCE TO PULL TERMINAL QUT OF CON Figure 6 3 Connector 4 Terminal Removal Connector Disassembly and Repair AC Electro Motor Cruise System Service Manual TASK FOUR Re form the locking tang if the lead and terminal in good condition re form the locking tang Step 1 Hold the lead firmly to prevent the splice between the terminal and the wire from flexing Step 2 Use the pick tool to bend the locking tang back into its original shape see Fi
27. ruise System Circuit Schematic 18 Block Diagram Electro Motor Cruise System 8 Schematic Symbol 13 Installation LB4 4 3L LO3 5 00 Cruise Module Connector Removal 20 LAE 9 Connector C4A Retainer Removal 21 Installation on LH6 amp LL4 6 2L Diesel 9 Connector C4A Terminal Removal 21 Installation on LIS 7 41 9 Re forming Locking Tang 22 Cruise Mode Switch Location Steering Column 10 Connector 4 Terminal 22 Clutch Release Switch Location Cable Installation Step 2 24 Behind Instrument Panel 10 Cable Installation Step 2 24 Brake Release Redundant Release Cable Installation Step 3 DNE Switch Location Behind Instrument 10 Cable Installation Step 4 2 25 Cruise Module Location Engine Cable Installation Step SA E Ne 25 Compartment Bulkhead 10 Cable Installation Step 5B 25 Wiring Harness Location Behind Cable Installation Step 6 25 Instrument Panel on Left 11 Cable Adjustment Diesel Lever 26 Convenience Center Location Cable Adjustment Step 4 27 Behind Instrument 11 Cable Adjustment Step 5
28. the clutch pedal is depressed the clutch switch disengages the cruise system The cruise system remains disengaged after the pedal is released Cruise Control Module The cruise control module see Figure 3 4 is mounted on the engine compartment bulkhead near the Master Cylinder The module replaces both the Electronic Con trol Module and the vacuum actuated Servo unit uti lized in the AC Custom Cruise III cruise system The cruise control module which includes an electronic controller and an electric motor varies the throttle with each different cruise mode command CAUTION The cruise control module is not dealer serviceable DO NOT TO REPAIR C Figure 3 2B Plunger Type Cruise Release Switch _ me Electro Motor Cruise Block Diagram and System Layout GMT 400 AC Electro Motor Cruise System Service Manual Component Relationship Figure 4 1 is a block diagram showing the component and operational relationships in the AC Electro Motor Cruise System The cruise control module using an electric motor and an electronic controller see Figure 3 4 operates the connecting strap and throttle linkage The module receives input signals from the turn signal mode Switches brake and clutch release switches and vehi cle speed circuitry The Internal Transmission Speed Sensor ITSS generates a high frequency sine wave which is converted to a square wave by the vehicle spee
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