SHIFT INTERLOCK SYSTEM
Transaxle is equipped with a shift lock and key lock system. Shift lock system prevents selector lever from being moved from Park unless brake pedal is depressed. In case of a malfunction, selector lever can be released by depressing shift lock override button located near selector lever. Key lock system prevents ignition key from being moved from ACC to LOCK position on ignition switch unless selector lever is in Park. For additional information on shift lock and key lock system, see appropriate SHIFT INTERLOCK SYSTEMS article.
ELECTRONIC CONTROL MODULE
The ECM monitors transaxle operation and contains a self-diagnostic system which stores DTCs if a transaxle electronic control system failure or problem exists. A malfunction Indicator Light (MIL) on instrument panel will illuminate to warn driver a malfunction has occurred. DTCs can be retrieved to determine transaxle problem area. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM.
ECM receives information from various input devices and uses this information to control shift solenoids and torque converter lock-up. To locate ECM (Scheme 19)
Scheme 19
Stop Light Switch
Stop light switch delivers input signal to ECM, indicating vehicle braking. Stop light switch is located on brake pedal support.
Counter Gear Speed Sensor
Counter gear speed sensor (NC) detects rotation of counter drive gear. By comparing counter gear speed sensor signal and input turbine speed sensor (NT) signal, ECM detects shift timing of gears and controls engine torque and hydraulic pressure in response to various conditions, resulting in smooth transaxle shifting. (Scheme 20)
Scheme 20
Engine Coolant Temperature Sensor
Engine coolant temperature sensor delivers input signal to ECM, indicating engine coolant temperature. ECT sensor is located at right rear corner of engine, near upper radiator hose.
Input Turbine Speed Sensor
Input turbine speed sensor (NC) detects rotation of input shaft. By comparing input turbine speed sensor signal and counter gear speed sensor signal, ECM detects shift timing of gears and controls engine torque and hydraulic pressure in response to various conditions, resulting in smooth transaxle shifting. (Scheme 20)
Park/Neutral Position Switch
Park/Neutral Position (PNP) switch delivers an input signal to ECM to indicate selector lever position. PNP switch is located on side of transaxle, below solenoid connector.
Throttle Position Sensor
TP sensor delivers an input signal to ECM indicating throttle position. TP sensor is located on side of throttle body.
Vehicle Speed Sensor
Vehicle speed signal is delivered to ABS ECU by ABS wheel speed sensors. ABS ECU converts signals into a 4-pulse signal and outputs signal to instrument cluster. Instrument cluster converts signal to a more precise waveform and outputs signal to ECM. Speed sensors are located at each wheel.
ECM OUTPUT DEVICES
Note. In case of a short in a shift solenoid circuit, ECM will stop sending current to the shift solenoid with the shorted circuit.
Shift Solenoid DSL
ECM uses signals from TP sensor, airflow meter and crankshaft position sensor to monitor torque converter lock-up engagement condition. ECM compares torque converter lock-up engagement condition with lock-up schedule in ECM memory to detect a malfunction with valve body, torque converter clutch or shift solenoid DSL. Shift solenoid DSL controls hydraulic pressure acting on lock-up relay valve, which contains torque converter clutch lock-up. Shift solenoid DSL is located on transaxle valve body. (Scheme 21)
Shift Solenoids SL1, SL2 & S4
ECM controls transaxle shifting by delivering an output signal to operate proper shift solenoid. Solenoids are located on transaxle valve body. (Scheme 21) Solenoids are operated in accordance with selector lever position. If a solenoid malfunctions, ECM defaults transaxle to a designated gear. (Scheme 22)
Note. ECM provides a fail-safe system which places transaxle in a designated gear depending on which solenoid fails. In some gears, fail-safe system will not be activated and transaxle will shift to the fail-safe gear. (Scheme 22)
Shift Solenoid SLT
ECM controls line pressure by sending a predetermined duty ratio to shift solenoid SLT, modulating line pressure and generating throttle pressure. Shift solenoid SLT is used to precisely and minutely modulate and generate line pressure according to accelerator pedal effort, or engine power output detected. Shift solenoid SLT is located on transaxle valve body. (Scheme 21)
Scheme 21
Scheme 22
The vehicle is equipped with a shift interlock and key lock system. The shift interlock system prevents the gearshift lever from being moved from the PARK position unless brake pedal is depressed. In case of a malfunction, the gearshift lever can be released by depressing the shift interlock override button located near the gearshift lever. The key lock system prevents ignition key from being moved from ACC to LOCK position on ignition switch unless the gearshift lever is in the PARK position. For more information on shift interlock and key lock system, see appropriate SHIFT INTERLOCK SYSTEMS article.
Harsh Engagement From Neutral To Drive
Check forward clutch accumulator, forward clutch, underdrive clutch and No. 1 one-way clutch.
Harsh Engagement From Neutral To Reverse
Check accumulators, lower valve body control valves, direct clutch and 1st/reverse brake.
Harsh Engagement From Neutral To Low
Check solenoid modulator valve.
Harsh Engagement During Upshift
Check upper valve body check, control and lock valves.
Harsh Lock-Up Engagement
Check lock-up relay valve and torque converter clutch.
No 1-2 Upshift
Check lower valve body control valves, 2nd brake and No. 1 one-way clutch.
No 2-3 Upshift
Check lower valve body control valves and direct clutch.
No 3-4 Upshift
Check 3-4 shift valve and underdrive clutch.
No Lock-Up Or Lock-Up Off
Check lock-up relay valve and torque converter clutch.
No 4-3 Downshift
Check 3-4 shift valve.
No 3-2 Downshift
Check lower valve body control valves.
No 2-1 Downshift
Check lower valve body control valves.
No Engine Braking In Low
Check solenoid modulator valve and 1st/reverse brake.
No Engine Braking In "2" Position
Check solenoid modulator valve and 2nd brake.
No Kickdown
Check lower valve body control valves and 3-4 shift valve.
Poor Acceleration (All Positions)
Check torque converter clutch and underdrive planetary gear.
Poor Acceleration In Overdrive
Check underdrive clutch and underdrive planetary gear.
Slip Or Shudder In 1st Gear
Check No. 1 one-way clutch.
Slip Or Shudder In 2nd Gear
Check 2nd brake and No. 2 one-way clutch.
Slip Or Shudder In 3rd Gear
Check direct clutch.
Slip Or Shudder In Overdrive
Check underdrive clutch.
Slip Or Shudder In Reverse
Check direct clutch and 1st/reverse brake.
Slip Or Shudder In Forward Position After Warm-Up
Check upper valve body, oil strainer, torque converter clutch, forward clutch, direct clutch, underdrive brake, No. 1 one-way clutch and underdrive clutch.
Vehicle Does Not Move In Any Forward Or Reverse Gear
Check manual valve, primary regulator valve, parking lock pawl, front planetary gear, rear planetary gear, underdrive planetary gear, forward clutch, underdrive brake and No. 2 one-way clutch.
Vehicle Does Not Move In Reverse
Check front planetary gear, rear planetary gear, underdrive planetary gear, direct clutch, underdrive brake and 1st/reverse brake.
"D" Position
- Place selector lever in "D" position. Hold accelerator pedal constant at full throttle. Check 1-2, 2-3 and 3-4 upshift and lock-up points. See appropriate table under «SHIFT SPEED SPECIFICATIONS»(ref-142323-S34174336702002072900000) . NOTE: There is no overdrive lock-up when coolant temperature is less than 128°F (55°C). There is no lock-up when brake pedal is depressed There in no 5th gear up-shift under the above conditions. If no 1-2 upshift occurs, check lower valve body control valves or shift solenoid. If no 2-3 upshift occurs, check lower valve body control valves or shift solenoid. If no 3-4 upshift occurs, check 3-4 shift valve or shift solenoid. If all shift points are incorrect, check upper valve body, lower valve body control valves and 3-4 shift valve. If all lock-up points are incorrect, check lock-up relay valve or shift solenoid.
- Use procedure outlined in step 1) to check for shock and slip between 1-2, 2-3 and 3-4 upshifts. If shock is harsh, line pressure may be too high. Check accumulator or check ball.
- Drive vehicle in "D" position lock-up or overdrive gear. Check for abnormal noise and vibration. NOTE: Check for cause of abnormal noise and vibration must be made with extreme care as problem could be due to an unbalanced axle shaft, differential, tire, torque converter, etc.
- While driving in "D" position, confirm correct kickdown vehicle speed limits for 2-1, 3-2, 4-3 shift points. Check for abnormal shock and slip at kickdown.
- Check lock-up function. Drive vehicle in overdrive in "D" position with lock-up on. Hold vehicle speed steady at 37 MPH. Lightly depress accelerator pedal. Ensure engine RPM does not change abruptly. Large increase in engine RPM indicates lock-up function is faulty.
"2" Position
- Place selector lever in "2" position. Drive vehicle with accelerator pedal held constantly at full throttle. Ensure 1-2 upshift points take place and are operating properly. NOTE: In "2" position, there will be no lock-up to 2nd gear.
- While driving in "2" position, release accelerator pedal and check engine braking effect. If there is no engine braking effect, 2nd brake is defective. Check for abnormal noise and shock at acceleration and deceleration.
"L" Position
While driving, place selector lever to "L" position and ensure there is no upshift to 2nd gear. While driving in "L" position, release accelerator pedal. If there is no engine braking effect, 1st/reverse brake is defective. Check for abnormal noise during acceleration and deceleration.
"R" Position
Place selector lever in "R" position. Accelerate in Reverse from a stop at full throttle. Ensure slipping does not occur.
"P" Position
Stop vehicle on grade of more than 5 percent. Place selector lever in "P" position. Release parking brake. Ensure parking lock pawl holds vehicle.
HYDRAULIC PRESSURE TESTS
| CAUTION | Perform test at normal operating fluid temperature of 122-176°F (50-80°C). |
- Ensure transaxle fluid is at operating temperature. Raise and support vehicle. Remove transaxle case test plugs. (Scheme 23) Install hydraulic pressure gauges. Lower vehicle.
- Fully apply parking brake. Block all wheels. Start engine and ensure idle speed is 650-750 RPM. Place selector lever in "D" position. Read and record pressures at idle. Fully apply brakes. Depress accelerator pedal to floor. DO NOT apply full throttle for more than 5 seconds.
- Measure highest line pressure. Refer to specifications. See «LINE PRESSURE SPECIFICATIONS»(ref-142323-S25531778582002072900000) table. Repeat test in "R" position. If pressures exceed specifications in all ranges, regulator valve or control valve in upper valve body is defective. Ensure no Throttle Position (TP) sensor-related trouble codes are present.
- If pressures in both positions are lower than specifications, oil pump, regulator valve or underdrive clutch is defective. Ensure no TP sensor related trouble codes are present.
- If pressure is lower than specifications in "D" position only, forward clutch is defective or "D" range circuit has a fluid leak. If pressure is lower than specifications in "R" position only, direct clutch is defective, 1st/reverse brake is defective or "R" range circuit has a fluid leak.
Scheme 23
| Engine RPM | "D" Range - psi (kg/cm 2 ) | "R" Range - psi (kg/cm 2 ) |
|---|---|---|
| Idle Speed | 54-60 (3.8-4.2) | 97-106 (6.8-7.5) |
| Stall Speed | 134-150 (9.5-10.5) | 256-286 (18.0-20.1) |
LINE PRESSURE SPECIFICATIONS
CIRCUIT TESTS
Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .
COMPONENT TESTS
Note. For circuit reference, see CONNECTOR IDENTIFICATION and/or WIRING DIAGRAMS .
Note. The following information may also be used to diagnose DTC P0770. For testing of shift solenoid SLT, see DTC P1760: SHIFT SOLENOID MALFUNCTION under DIAGNOSTIC TESTS.
Scheme 24
- Raise and support vehicle. Remove transaxle oil pan. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Remove shift solenoid DSL. (Scheme 21) Connect battery voltage to solenoid. Apply 71 psi (5 kg/cm 2 ) of compressed air to solenoid with battery voltage connected. (Scheme 24)
- With battery voltage connected, air should not pass through solenoid. Disconnect voltage to solenoid. Ensure air passes through solenoid. Replace solenoid as necessary.
SHIFT SOLENOIDS SL1, SL2, SL3, SR & S4
Note. The following information may also be used to diagnose DTCs P0750, P0755, P0760, P0765 and P1815. For testing of shift solenoid SLT, see DTC P1760: SHIFT SOLENOID MALFUNCTION under DIAGNOSTIC TESTS.
Shift Solenoids SL1, SL2 & SL3
Raise and support vehicle. Remove transaxle oil pan. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Remove shift solenoid(s). (Scheme 21) Using a DVOM, measure resistance between shift solenoid terminals. Resistance should be 5.1-5.5 ohms for each solenoid. If resistance is not as specified, replace faulty solenoid.
To check shift solenoid operation, connect terminal No. 1 of solenoid to battery positive using a test lead with an in-line 23-watt bulb. Connect terminal No. 2 of solenoid to ground. With power supplied to solenoid, ensure solenoid valve moves outward. With power disconnected, ensure solenoid valve moves inward. If solenoid does not operate as described, replace solenoid. If solenoid operates, diagnose valve body malfunction.
Shift Solenoids SR & S4
Raise and support vehicle. Remove transaxle oil pan. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Remove shift solenoid(s). (Scheme 21) Measure resistance terminal of each solenoid. see scheme 12 Resistance should be 11-15 ohms at 68°F (20°C). If resistance is not as specified, replace faulty solenoid.
To check shift solenoid S4 operation, connect solenoid terminal to battery positive using a test lead with an in-line 23-watt bulb. Connect solenoid body to ground. see scheme 13 With power supplied to solenoid, ensure solenoid valve moves outward. With power disconnected, ensure solenoid valve moves inward. If solenoid does not operate as described, replace solenoid. If solenoid operates, diagnose valve body malfunction.
On models with cruise control (2-pin connector), continuity should exist between terminals No. 1 and 2 with brake pedal depressed and should not exist with brake pedal released. On models with cruise control (4-pin connector), continuity should exist between terminals No. 1 and 2 with brake pedal depressed and should not exist with brake pedal released. Continuity should not exist between terminals No. 3 and 4 with brake pedal depressed and should exist with brake pedal released. (Scheme 25) Replace switch if continuity is not as specified.
Scheme 25
PIN VOLTAGE TESTS
Access ECM located behind glove compartment. Turn ignition switch to ON position. Using a DVOM, backprobe ECM harness connector. Measure voltage between specified terminals. (Scheme 26) Ensure voltage is as specified.
