Winter 04 - The Subaru SVX World Network
Contents
1. SENSOR Throttle Sensor The throttle sensor idle switch is basically electrical throttle pressure The load signal affects shifting line pres sure and lock up The closed throttle input affects the lock up release mode as well as smooth downshifting into 2nd gear It also causes a reduction in the pressure Vehicle speed sensor 1 is mounted to the transmission and is basically electrical governor pressure It is used to detect vehicle speed and it affects shift points lock up and line pressure In FWD transmissions the speed sensor reads parking gear rotation at the front output shaft In AWD transmis sions it senses the transfer clutch drum rotation at the rear output shaft Vehicle speed sensor 2 is built into the combination meter In FWD units it is used as a back up for speed sen sor 1 In AWD units it is used as the front output shaft speed sensor An electric speedometer system was first introduced on the SVX in 1992 It was later added to the 1995 Legacy 1996 Impreza and 1998 Forester The system uses a Magnetic Winter 2004 gt Number 25 5 4EAT Transmission Diagnosis amp Service Resistance Effect MRE speed sensor driven by a con ventional speedometer drive gear system The speed sensor which generates four pulses per revolution is located on the front differential housing The Speedometer Driving Unit SDU receiving pulses from the MRE sensor processes the signal send ing the information t2. seconds to full engagement It should take less than 1 2 seconds Then shift into R and measure the time It should take less than 1 5 seconds Time Lag Results If the time takes longer from N to D it may indicate one or more of the following Low line pressure Worn forward clutch OWC problem If the time takes longer from N to R it may indicate one or more of the following Low line pressure Worn reverse clutch Worn low rev brake Pressure Test Perform a pressure test when all the circuits show evidence of slippage or when the circuits show negative results from the time lag test This test should also be performed if there is excessive shift shock delayed shifting or it the vehicle is immobile Perform this test by connecting the pressure gauge to the oil pump outlet test port in order to determine the overall line pressure Should a particular component be suspected perform pressure tests at its unique test port Check for minimum and maximum values at each port Transmission Pressure Test Port On Car Service Adjustments The following can be performed on the vehicle Checking changing fluids Band adjustment Valve body servicing Shift Linkage adjustment replacement Inhibitor switch adjustment replacement Harness repair replacement Transfer clutch assembly servicing replacement Speed sensors replacement www endwrench com
3. Impreza amp Forester The manual light is activated when the manual button is depressed On the 1990 91 model year the 3 2 1 light box changed color from green to yellow This fea ture was discontinued in the 1992 model year The Manual Light and Switch were discontinued in all models but the SVX in 1995 The POWER light is activated momentarily whenev er the vehicle is started The computer monitoring how quickly the gas pedal is depressed selects the POWER mode This changes the performance characteristics of the transmission It delays upshifts and may downshift if necessary When selected the computer turns the POWER light ON The POWER light was eliminated on Legacy beginning with the 1995 model year but the TCU logic is the same www endwrench com Note There are a number of predetermined rates based on the relation ship between vehicle speed and throttle angle These determine ease of access to the power mode As a general rule it is easier to activate power mode at lower speeds from a light throttle than it is at higher speeds from a light throttle Power Pattern Mode increases up and down shift points It is deactivated by vehicle speed and throttle angle For example if speed is equal to or greater than approximate ly 40 MPH with a light throttle deactivation is immediate Conversely if the speed is less than approximately 40 MPH a time lag up to 3 seconds will occur before resuming nor mal shift patter
4. N D 3 2 1 The 1 HOLD button has been deleted and a manual button has been added When the selector is in 3rd range manual switch ON the transmission will start in 2nd gear and shift to 3rd In 2nd range XT Selector Lever www endwrench com manual the transmission starts and stays in 2nd gear but will upshift to 3rd gear at 6500 RPM to prevent damage to the engine In 1st range manual the transmission stays in 1st gear and also will upshift to second at 6100 RPM to prevent dam age to the engine Additionally on all wheel drive AWD vehicles the TCU applies a more aggressive AWD map when the selector is in the 1st position manual switch ON or OFF These changes result in improved driveability on low traction road surfaces In 1995 the manual button was deleted When 3 is select ed the transmission shifts through1st 2nd and 3rd When 2 is selected the transmission shifts 1st and 2nd When Ist is selected the transmis sion stays in Ist On 1995 through 1998 ist 2 785 model year vehicles the ond 1 545 TCU controlled upshift 3rd 1 000 logic was replaced by a Ath 0 694 ON re Pe eee ae Final Drive 3 70 1 or 3 90 1 introduced with fuel cut Ax Esa RT logic never having an 3 70 1 FWD auto up shift logic 1992 through 1997 Refer to Service Manual for specific model gear ratios SVX used the same shift logic as the 1990 94 Legacy The Manual but ton was retained until production of the vehicle was discon
5. mode detected by the TCM The TCM continuously monitors the torque convert er clutch system A fault will register if the following condition is present The End Wrench HARA HA A HRA Torque Converter Clutch Monitor Engine speed is equal to or greater than output shaft speed speed sensor 1 multiplied 4th gear ratio multi plied by 9 8 The following conditions must be met before the test is performed 1 The transmission is in 4th gear 2 The duty ratio for lockup duty solenoid is equal to or greater than 90 The DTC will set and the MIL will illuminate if a fault is registered during two consecutive trips Control Unit Networking Engine Speed Signal Torque Control Cut Signal Mass Air Flow Signal AT Diagnosis Input Signal fifa 1 Fol s B40 B78 OBD Il Data Link Connector Service Connector Connector Both the Fuel Injection control unit and the Transmission control unit share processed information and sensor input by shared signals Engine speed signal is sent to the TCM from the ECM influencing Torque Converter lock up Torque Control Cut signal is sent to the TCM from the ECM preventing fuel cut under certain condi tions Diagnostics are provided by the TCM as code 16 signal diagnostics are not provided in OBD II www endwrench com Torque control signal unique from the Torque Control Cut signal is created in the TCM logic to communicate to the ECM that to
6. EAT Ph ase 1 sor controlled transmission that was installed in many 1987 5 98 Subaru vehicles It is not a three speed transmission with overdrive It features a lock up torque converter which locks up in all forward gears except 1st T he Subaru 4EAT is a four speed microproces 4EAT assembly The shift quadrant has been designed in accor dance with the four forward speeds In P R or N there aren t any special features With the selector in D the transmission shifts through all four gears With the selector in 3 the transmission shifts 1 2 3 When the selector is in the 2 position the trans mission shifts through 1st and 2nd If necessary 3rd The End Wrench ransmission iagnosis ree Te ey gear is computer selected to prevent the engine from over revving Manual 1st gear is only activated when the 1 HOLD button is depressed and the shifter is in manually selected 2 This will provide engine brak ing The transmission will upshift through 2nd and 3rd if necessary in order to prevent the engine from over revving The 1 HOLD indicator is displayed on the com bination meter when the button is activated When the computer overrides the 1 HOLD gear selection the display will change An enhanced version of the 4EAT was intro duced with the 1990 asad Although similar in design to the earlier z 4EAT the shift quadrant is different The Legacy 4EAT has a seven posi tion quadrant P R
7. and double check the operation After adjusting the gearshift cable verify the correct inhibitor switch position Remove the cable from the inhibitor switch in order to perform the adjustment The switch must be in neutral Then insert the special tool 499267300 Stopper Pin available from Kent Moore by calling 800 345 2233 through the two levers of the switch into the depression in the switch body Next loosen the three retaining bolts and rotate the inhibitor to adjust Finally reinstall the cable and reconfirm the cable adjustment Oa 499267300 Inhibitor Switch Adjustment Stall Test The stall test checks the operating condition of the AT clutches the torque converter and the engine Perform these checks in D 3 2 and Reverse Stall Test Results Higher than normal RPM indicates one or more of the following Slippage of the forward clutch One way clutch OWC not holding Low Rey brake slipping Overall low line pressure Lower than normal RPM indicates one or more of the following Incorrect throttle adjustment Poor engine operation Torque converter stator slippage Time Lag Test The time lag test checks the operation of the forward clutch the reverse clutch the low reverse brake OWC 3 4 and OWC 1 2 The End Wrench Perform this test at operating temperature Idle the engine with the NC OFF Confirm the proper idle speed in N and correct if necessary Then shift into D and measure the time
8. ck Duty Solenoid C is located in the extension housing It is also controlled by the TCU It varies the degree of AWD Combination Meter Light Operation XT 6 and L Series The XT 6 and L Series gear indicator bar is located in the combination meter shift position indicator Controlled by the TCU other quadrant indicators are controlled by the inhibitor switch both providing a path to ground 2nd indicator bar is affected by the 1 HOLD switch input With the 1 HOLD button switched OFF amp the shift selector in the 2nd Select position the TCU grounds the 2nd indicator light circuit illuminating the 2nd gear indicator The 1 HOLD indicator light L and XT only is locat ed near the shift position indicator It is activated by the TCU whenever the 1 HOLD button is depressed with the shift lever in 2 It changes the display and cancels the 2 indicator The vehicle stays in 1 HOLD unless the TCU deter mines a potential engine over rev condition at which point the transmission will then upshift Note When 1 HOLD is activated all other shifting inputs are ignored ATF temperature warning light was used on AWD vehi cles only indicates overheating ATF See description of TCU inputs for control unit logic in response of hot ATF The Power indicator was a frame that illuminates around the word POWER on the combination meter Activation logic of the power mode is the same as later models Late Model Combination Meter Legacy SVX
9. d year vehicle the data list displayed can be extensive OBD II functions also have freeze frame data on 1995 and newer Subaru vehicles 1995 98 Legacy 1996 98 Impreza 1996 97 SVX 1998 Forester Diagnostics OBD II Vehicles The AT Oil Temperature light operates under the fol lowing conditions Ignition switch ON engine OFF is the bulb check mode the light remains ON Normal Ignition switch ON Engine ON light remains on for two seconds from engine start www endwrench com Note A failure is never reported via the AT oil temp light during current operation The TCU waits until the next ignition cycle to dis play the following AT oil temp light condition Therefore the driver may detect an abnormal driveability condition fail safe operation with no AT oil temp light indicating a failure Abnormal With the ignition switch ON and the engine running the light remains ON for 2 seconds from engine start OFF for 0 25 seconds ON for 0 25 seconds 4 times then OFF for 2 seconds Cycle repeats 4 times for a total of 16 Blinks Abnormal ATF Temperature is too high The AT temp light comes ON and stays ON until the ATF temperature returns to normal Trouble Codes Trouble code retrieval is similar to previous models except for grounding terminal 5 of connector B82 a 6 pole black right side of steering column Trouble codes will be displayed through AT Temp light with the following differences There are 14 possible tro
10. located on the upper valve body It is used to control downshifts It quickly releases the 3 Release pressure during low speed heavy load situation in order to provide smooth 3 2 downshifts It operates the overrunning clutch in order to provide engine brak ing during deceleration It is also used to cancel the overrunning clutch momentarily during light throttle 3 2 downshifts or closed throttle 2 1 downshifts This reduces the shift shock Duty Solenoid A is located on the upper valve body It regulates line pressure at 3 levels Basic Altered with load vehicle speed and range signal Shifting Lower line pressure in between shifts to minimize shift shock Start up With low ATF temperature or a low tachometer signal cranking speed it sets line pres sure to a minimum Dropping Resistor The dropping resistor is wired in parallel with duty solenoid A and is used to regulate line pressure It is located on the right front shock tower behind the MPI fuel system dropping resistor It takes over line pressure control during the OFF portion of the duty cycle for the duty solenoid In other words the duty solenoid is never fully OFF Duty Solenoid B The End Wrench Duty Solenoid B is located on the lower valve body next to the ATF temperature sensor It operates the lock up clutch in 3 modes ON OFF and a gradual ON OFF control of the lock up clutch during gear shifting in order to reduce shift sho
11. lure has no effect If multiple signals are seen in the forward ranges the inhibitor switch is ignored and there is no fourth gear If the 1 HOLD switch is defective the system operates in the same manner as an inhibitor switch failure in the for ward ranges If the MANUAL switch is defective Legacy only the transmission will shift normally in D position It will oper ate the same as an inhibitor switch failure when the selector position 3 2 1 Winter 2004 gt Number 25 11 4EAT Transmission Diagnosis amp Service If shift solenoids 1 or 2 malfunction the TCU deactivates the other This results in either 3rd gear or Reverse when selected If duty solenoid A fails line pressure goes to maximum If duty solenoid B fails the torque converter lock up will not occur If shift solenoid 3 malfunctions the overrunning clutch is always ON and there will be engine braking during deceleration If duty solenoid C should fail the AWD control will be set to maximum and the rear wheels will always be powered Self Diagnostic System The 4EAT self diagnostic system has three modes a user mode and two dealer modes In the first instance the user is notified through the POWER light when a malfunction occurs The failure is com municated after the next ignition OFF ON cycle Por a more detailed description of the user mode see the appropriate troubleshooting section of the service manual Note The sys
12. n ATF temperature warning light is provided on both FWD and AWD vehicles It is activated by the TCU indicating over heated ATF The TCU logic will shift the transaxle as if in the power mode moving more ATF volume through the cooler The indicator light was discontinued in the 1993 model year but the logic for controlling hot ATF remained Starting in the 1995 model year the HOT ATF indicator light was reintroduced It performs the same as in the past with an added function When the vehicle is started it is lit momentarily If it is flashing when the vehicle is started this indicates the TCU has detected an electrical failure When the TCU is programmed to do so it will flash a trouble code to assist in diagnostics Fail Safe System Note The 4EAT is a highly reliable transmission Should an electrical component malfunction it will enter failsafe mode Fail Safe Components and Failure Results If a speed sensor fails the remaining sensor signal will be used In case of throttle sensor failure the idle contacts will signal the throttle opening Line pressure will go to maximum at open throttle and it will go to minimum at closed throttle Although the inhibitor switch may fail the manual valve will still be in the correct position for all selected ranges In P and N however it may affect start up therefore there is a potential for a no start condition In Reverse the TCU is passive Therefore an inhibitor switch fai
13. o the FWD connector located under the hood Failure to do so could result in movement of vehicle TCU Outputs There are two types of outputs solenoid controls and light controls The solenoids control shifting line pres sure lock up and AWD www endwrench com B A Shift Solenoids and Valves The light controls indicate operating conditions to the driver They indicate the POWER mode manually selected Ist or 2nd gear or hot ATF AWD only On 1990 and later Legacy models the light controls indicate hot ATF FWD and AWD gears 3 2 1 MAN UAL mode and POWER mode Shift solenoids 1 and 2 are located on the upper valve body The TCU induces ON OFF conditions which regulate the shifting of the forward gears When a shift solenoid is ON it passes pilot pressure to shift valve A and or shift valve B The valve s will then shift feeding the appropriate controlling member circuits high clutch band etc Note Pilot pressure is nothing more than a pressure held at a con stant value When a shift solenoid is OFF the affected shift valve will move to its static position due to spring pressure The appro priate controlling member circuit will than be fed high clutch band etc COMPONENT APPLICATION REV C B B HIGH C FWD C OWC OVR C Lo OWC Sol 1 Sol 2 3 4 REV B 1 2 Winter 2004 e Number 25 9 4EAT Transmission Diagnosis amp Service Shift Modes Shift solenoid 3 is
14. o the transmission control unit The TCU compares the speed signal from the front output shaft with the signal from the rear output shaft sensor 1 The speed differential helps the TCU determine the degree of AWD along with other inputs The tachometer signal affects the shift points at kick down The TCU uses the signal to prevent the engine from over revving Note The TCU will override the inhibitor switch if necessary to prevent the engine from over revving The cruise control signal tells the TCU of cruise con trol activation This allows for a wider operating range in 4th gear unless a large speed differential exists from the set speed in which case the transmission may downshift This improves fuel economy ATF Temperature Sensor The ATF temperature sensor is located on the lower valve body next to duty solenoid B When the ATF is cold the TCU won t allow an upshift into 4th gear The object is to warm the engine quickly for lower emissions It is more sophisticated than the KDLH sys tem and less objectionable for the consumer When the ATF is hot AWD only the TCU shifts the transmission as if in the POWER mode This push es the shift points higher which allows the engine to run faster The oil pump then circulates ATF through the oil cooler more quickly so as not to overheat the engine coolant TheTCU also monitors system voltage in order to cor rectly interpret the inputs and alter the control of the
15. outputs For example the system is designed for 12 volt The End Wrench operation When running however most vehicles have other than 12 volts available The 1 HOLD switch is located aft of the shift quadrant When activated it creates a forced 1st gear Note The TCU will shift 2nd to 3rd if necessary to prevent the engine from over revving FWD Fuse The FWD fuse changes the driving mode from AWD to FWD The FWD fuse is located on the left front shock tower It is activated by inserting the spare fuse into the under hood connector The FWD light on the combina tion meter verifies that the vehicle is in FWD The Legacy FWD fuse is located on the right strut tower The SVX and Forester fuse is located in the main fuse box Legacy TCU Inputs The Legacy fuel system ECM beginning with the 1990 model year sends new inputs to the TCU for line pressure control It networks the MPFI ECU RPM sig nal and altitude compensation inputs This provides additional line pressure control for high altitude com pensation to reduce shift shock ABS system inputs turn OFF the over running clutch when ABS is active and fixes the duty ratio of the MPT to mostly FWD Maintenance Precautions Before jacking up one or two wheels for mainte nance with the engine running or before running the vehicle on a chassis dynamometer the electronic AWD engagement system must be disengaged by installing the spare fuse 15A of the fuse box int
16. rammed for self diagnostics Shift Solenoid 1 defective position 4 in sequence POWER light OFF for 25 seconds light ON for 2 seconds 3 flashes at 10 duty 0 1 second 4th flash at 60 duty 0 6 seconds 7 flashes at 10 duty cycle repeats 1990 94 Legacy 1992 95 SVX 1993 95 Impreza Diagnostics The procedure to retrieve trouble codes is similar to previous years The manual button replaces the 1 HOLD button function Three modes are available Current trouble codes Past trouble codes Long term memory Clear memory The codes are communicated on the POWER light There are 12 codes for the AWD and 11 codes for the FWD vehicles They are displayed similar to fuel system codes one long flash 10 1 2 seconds one short flash 1 0 3 seconds For example one long two short Code 12 Select Monitor Analysis The Select Monitor is a powerful tool for analysis of an electrical condition This form of analysis is the preferred troubleshoot ing self diagnostic method The Select Monitor identi fies current problems past problems through long term memory and indicated actual circuit and component performance Other functions that can be useful diagnostic aids are graphing LED display of switched components Max amp Min readings and save data and play back Also the Select Monitor Oscilloscope function serves to assist in finding intermittent electrical conditions using the trigger function Depending on the model an
17. rque reduction fuel cut is required to reduce shift shock during a wide open throttle upshift Diagnostics are provided by the TCM as code 25 and also in OBD II logic as DTC P1103 The Mass Airflow signal is sent to the TCM from the ECM as a back up for influencing the shift points in the event of a throttle position signal loss Line pressure is also affected by the Mass Airflow sensor input lowering the line pressure during up shifts reducing shock There are no corresponding onboard diagnostic codes for this signal in the TCM Automatic Transmission Diagnosis Input Signals represent an electrical check for the circuit that networks the TCM and ECM communicating diagnostic information to the ECM This signal has no corresponding 4EAT code Troubleshooting and Adjustments Preliminary Inspection Check the following 1 Fluid level 2 ATF leaks 3 Road Test Check proper shift points Engine performance Correctly adjusted throttle sensor Gearshift cable adjustment Correct stall test results Inhibitor switch connections Correct pressure test results 4 5 6 ve 8 Gearshift Cable Adjustment Cable Adjustment Winter 2004 gt Number 25 15 16 Place the transmission in neutral with the engine OFF Then loosen the locking nut and the adjusting nut Push the shift lever arm rearward and tighten the adjusting nut until it contacts the connecting block Finally secure the cable with the locking nut
18. t established DTCs that are to be used by the automobile industry beginning with the 1996 model year DTCs that use a PO prefix are SAE assigned DTCs that use a P1 prefix are categorized by SAE but are assigned by a vehicle manufacturer OBD II checks a component and its operation similar to OBD 1 which is used on pre 1995 model vehicles OBD for example checks the Torque Converter Clutch System Electrical by monitoring for minimum and maximum voltage signals OBD II also performs this function For example examine DTC P0743 The TCM continuously monitors duty solenoid B Circuit A fault will register if the following conditions are met 1 When the TCM supplies an ON signal to the coil of the solenoid the voltage from the coil is lower than pre established parameters 2 When the TCM supplies an OFF signal to the coil of the solenoid the voltage from the coil is higher than pre established parameters Bae TCM Monitor Condition a or b will cause the DTC to register in the ECM memory on OBD I or OBD II systems OBD II in addition to the previous will monitor for performance of the Torque Converter Clutch System For example examine DTC P0740 The detecting condition Slipped wheel RPM absolute value of difference from transmission input RPM computed from engine speed and vehicle speed continues greater than 40 vehicle speed 2 for 10 2 seconds When the lockup duty ratio is greater then 90 in lock up control
19. tem will fail safe for limp home when a component fails The light will not illuminate until the ignition is switched OFF and then switched to ON again For specific information on the self diagnostics deal er modes see the appropriate trouble shooting section of the service manual XT and L Series Diagnostics To enter into the dealer mode to retrieve trouble codes it is necessary to operate the inhibitor switch in a specific sequence as outlined in the service manual Once this has been performed the POWER light will flash a code sequence Shift Solenoid NO 3 Shift Solenoid NO 2 Duty Solenoid B Duty Solenoid C ATF Temp Sensor Ignition Pulse ae Solenoid A Throttle Sensor Speed Sensor NO 2 Speed Sensor NO 1 a ON Repeat Seconds ON 129 2 i1 Seconds TheTCU checks 11 components and displays the codes differently than other on board diagnostic functions When activated the POWER light flashes OFF for 2 5 seconds ON for 2 5 seconds then 11 flashes This sequence will repeat after the 11th flash The End Wrench Each component is assigned a position in the sequence i e ignition pulse is position 10 and each position has a duty cycle of one second Normal functioning components Flash on at a 10 duty light ON for 0 1 second light OFF for 0 9 second Malfunctioning components flash on at a 60 duty light ON for 0 6 second light OFF for 0 4 second Example TCU prog
20. tinued in 1997 The TCU monitors various engine and vehicle inputs i e throttle posi tion and vehicle speed etc It also controls the electronic shift solenoids in the transmission TCU Electronic Control System Overview The electronic control system consists of various inputs sensors and outputs lights and solenoids in addition to the Transmission Control Unit TCU This is the second generation of Subaru automatic transmission In addition to being smoother and quieter it is designed to help maximize fuel economy while pro viding performance It monitors the engine and transmission performance con ditions the driver s demands and the vehicle speed Transmission Control Unit The TCU is a highly sophisticated microprocessor with a self diagnostic long term memory It also has a failsafe func tion which maintains driveability in case of a major electri cal component failure BI 71E In a transmission equipped for AWD the TCU utilizes a program which continually changes the degree of AWD based upon vehicle operating condition s The TCU controls shifting and line pressure in addition to the lock up torque converter and the MPT clutch TCU Inputs Throttle sensor idle switch Vehicle speed sensor 1 Vehicle speed sensor 2 Tachometer signal Inhibitor switch Cruise control signal ATF temperature sensor Ignition battery voltage 1 HOLD switch Forced front wheel drive FWD Nit BOTTLE
21. uble codes communicated from the TCU They are displayed in the same format as old fuel system trou ble codes long Flash 10 short flash 1 For example 2 long and 4 short code 24 Duty Solenoid C The clear memory procedure is simple and quick just remove fuse No 14 for at least one minute Eco TCM Rey IC ATF Temp Check Engine Trans Dia gnosis OBD Il Current Code Current Code Memory Code gt Memory Code reeze Frame Data OBD II Logic Tree OBD II Operation Overview The system monitors components and their operation conducting continuity and performance checks The check engine light or MIL illuminates when a code is set into ECU memory Problems with the 4EAT are communicated from the TCU to the ECU There are 2 trouble codes that are generated as soon as a problem occurs turning on the MIL With 22 others requir ing a fault or error during two consecutive trips before turn ing on the MIL A trip is defined as a driving pattern in which test parameters are reached for a given time A failed trip will be erased if the next trip is a good one Winter 2004 gt Number 25 13 14 Transmission codes generated in OBD II have freeze frame information available on the Select Monitor in the fuel system section of data display OBD II Purpose The Society of Automotive Engineers SAE in coop eration with the EPA have in accordance with regulation J2012 of the 1990 Clean Air Ac
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