Automatic Transmission Diagnosis - U-340-E & U-341-E: Other Toyota Echo I

ENGINE CONTROL MODULE

ECM receives information from various input devices and uses this information to control shift solenoids and torque converter lock-up. ECM contains a self-diagnostic system, which will store a Diagnostic Trouble Code (DTC) if failure or problem exists in the electronic control system.

DTC can be retrieved to determine transaxle problem area. See SELF-DIAGNOSTIC SYSTEM. On Celica, ECM is located in engine compartment, near battery. On ECHO, ECM is located behind glove compartment. (Scheme 17)and (Scheme 18).

Park/Neutral Position Switch Signal

PNP switch delivers an input signal to ECM indicating selector lever position. Switch is located on side of transaxle.

Shift Switch (Celica)

When gearshift lever is in "M" position, the shift range can be switched UP or DOWN using the shift switch located on the steering wheel. Shifting is limited to the maximum gear step and enables automatic shift-up and shift-down within the allowable range.

Throttle Position Sensor Signal

TP sensor delivers an input signal to ECM indicating throttle position. TP sensor is located on side of throttle body.

Vehicle Speed Sensor Signal

VSS detects transaxle output shaft RPM. (Scheme 17)and (Scheme 18). VSS outputs a 4-pulse signal for every revolution of transaxle output shaft. Signal is converted into a more precise rectangular wave form by combination meter. Signal is then delivered to ECM. Gear shift point and lock-up timing are controlled by ECM based on signals from vehicle speed sensor and throttle position sensor.

Input Turbine Speed Sensor

Note. Also referred to as NT speed sensor and O/D direct clutch speed sensor on Celica.

Input turbine speed sensor detects rotation of input shaft. By comparing input turbine speed sensor signal and vehicle 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. Input turbine speed sensor is located on transaxle. (Scheme 17)and (Scheme 18).

Brakelight Switch Signal

Brakelight switch delivers input signal to ECM, indicating vehicle braking. Brakelight switch is located on brake pedal support.

O/D Switch Signal

O/D switch provides an input signal to ECM to indicate when overdrive is selected by vehicle operator. O/D switch is mounted on selector lever.

Engine Coolant Temperature Sensor Signal

Coolant temperature sensor delivers input signal to ECM, indicating engine coolant temperature. Engine coolant temperature sensor is located at right rear of cylinder head.

ATF Temperature Sensor

ATF temperature sensor, located on wiring harness inside transaxle oil pan, converts fluid temperature into a resistance value, which is input to ECM. (Scheme 19)

Cruise Control Electronic Control Unit (Celica)

Cruise control ECU delivers an input signal to control overdrive operation in accordance with vehicle speed when cruise control is operating. When in overdrive with cruise control on, if vehicle speed drops 10 MPH less than set speed, overdrive is released to prevent reduction in vehicle speed. Once vehicle speed is more than set speed, overdrive is resumed. Cruise control ECU is located behind instrument panel on driver's side of vehicle.

Scheme 17

Scheme 18

Scheme 19

Shift Solenoid No. 1 & No. 2

Note. Shift solenoids also be referred to as S1 and S2 solenoid.

ECM controls transaxle shifting by delivering an output signal to operate proper solenoid. Solenoids are located on transaxle valve body. (Scheme 20) Solenoids are operated in accordance with selector lever position. If a solenoid malfunctions, fail-safe gear may be selected. (Scheme 21)

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 21)

Shift Solenoid SL

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 SL. Shift solenoid SL controls hydraulic pressure acting on lock-up relay valve, which contains torque converter clutch lock-up. Shift solenoid SL is located on transaxle valve body. (Scheme 20)

Shift Solenoid ST

ECM sends a signal to shift solenoid ST to turn solenoid on and off. This controls 2nd brake timing by operating orifice control valve located in valve body. Solenoid is operated during application and release of reverse clutch. Shift solenoid ST is located on valve body. (Scheme 20)

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 20)

Scheme 20

Scheme 21

SHIFT INTERLOCK SYSTEM

Note. For system description and repair information, see appropriate SHIFT INTERLOCK SYSTEMS article.

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, forward clutch, reverse clutch, 1st/reverse brake and No. 2 one-way clutch.

Vehicle Does Not Move In Reverse

Check front planetary gear, rear planetary gear, reverse clutch and 1st/reverse brake.

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 2nd coast and O/D brake.

No Lock-Up Or Lock-Up Off

Check lock-up relay valve, lock-up control valve, solenoid relay valve, solenoid modulator valve and torque converter clutch.

No 4-3 Downshift

Check 3-4 shift valve.

No 3-2 Downshift

Check 2-3 shift valve.

No 2-1 Downshift

Check 1-2 shift valve.

Harsh Engagement Neutral To Drive

Check forward clutch accumulator, forward clutch and No. 2 one-way clutch.

Harsh Engagement Neutral To Reverse

Check accumulators, lower valve body control valves, reverse clutch and 1st/reverse brake.

Harsh Engagement Neutral To Low

Check solenoid modulator valve.

Harsh Lock-Up Engagement

Check lock-up relay valve and torque converter clutch.

Harsh Engagement During Upshift

Check accumulator control valve and accumulators.

No Engine Braking In Low

Check reverse control valve and 1st/reverse brake.

No Engine Braking In "2" Position

Check 3-4 shift valve and 2nd coast and O/D brake.

No Kickdown

Check lower valve body control valves and 3-4 shift valve.

Slip Or Shudder In 1st Gear

Check No. 2 one-way clutch.

Slip Or Shudder In 2nd Gear

Check 2nd brake and No. 1 one-way clutch.

Slip Or Shudder In 3rd Gear

Check direct clutch.

Slip Or Shudder In Overdrive

Check 2nd coast and O/D brake.

Slip Or Shudder In Reverse

Check reverse 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, 2nd coast and O/D brake, 2nd brake and No. 1 one-way clutch.

Poor Acceleration (All Positions)

Check torque converter clutch.

"D" Position

1. Shift transaxle into Drive. Hold accelerator pedal constant at full throttle. Check 1-2, 2-3, and 3-4 upshift and lock-up points. See appropriate table in «SHIFT SPEED SPECIFICATIONS»(ref-140773-S06153994972002052900000) and «LOCK-UP SPEED SPECIFICATIONS»(ref-140773-S33939038362002053100000) . NOTE: There is no overdrive lock-up when coolant temperature is below 140°F (60°C) or when vehicle speed is 6 MPH less than the set cruise control speed. There is no lock-up when brake pedal is depressed. 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.
2. 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.
3. Drive vehicle in Drive during lock-up or Overdrive. 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 drive axle, differential, tire, torque converter, etc.
4. While driving in Drive, confirm correct kickdown vehicle speed limits for 2-1, 3-2, 4-3 shift points. Check for abnormal shock and slip at kickdown.
5. Check lock-up function. Drive vehicle in Overdrive ("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

1. Shift transaxle to manual 2nd gear. 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.
2. While driving in manual 2nd gear, 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 in Low, ensure there is no upshift to 2nd gear. While driving in Low, 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

Shift transaxle into Reverse. 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. Shift transaxle into Park. Release parking brake. Ensure parking pawl holds vehicle.

HYDRAULIC PRESSURE TESTS

1. Ensure transaxle fluid is at operating temperature. Raise and support vehicle. Remove transaxle case line pressure test plug. (Scheme 22) Install hydraulic pressure gauge. Lower vehicle.
2. Fully apply parking brake. Block all wheels. Start engine and ensure idle speed is 700-800 RPM on Celica, or 650-750 RPM on ECHO. Shift transaxle into Drive. Read and record line pressure at idle. Fully apply brakes. Depress accelerator pedal to floor. DO NOT apply full throttle for more than 10 seconds.
3. Measure highest line pressure. Refer to specifications in appropriate LINE PRESSURE SPECIFICATIONS table. Repeat test in Reverse. If pressures exceed specifications in all ranges, regulator valve or shift solenoid SLT in upper valve body is defective. Ensure no TP sensor related trouble codes are present.
4. If pressures in both positions are lower than specifications, oil pump, regulator valve or shift solenoid SLT is defective. Ensure no TP sensor related trouble codes are present.
5. If pressure is lower than specifications in Drive only, forward clutch is defective or Drive circuit has a fluid leak. If pressure is lower than specifications in Reverse only, reverse clutch is defective, 1st/reverse brake is defective or Reverse circuit has a fluid leak.

Scheme 22

LINE PRESSURE SPECIFICATIONS (CELICA)

LINE PRESSURE SPECIFICATIONS (ECHO)

NORMAL Mode Code Retrieval

1. Connect scan tool to Data Link Connector (DLC3). (Scheme 23) DLC3 is located under left side of instrument panel. Turn ignition on with engine off. Turn scan tool on. Using scan tool manufacturer's instructions, check for DTCs and freeze-frame data.
2. If scan tool displays UNABLE TO CONNECT TO VEHICLE, DLC3 must be checked. See «DLC3 INSPECTION»(ref-140773-S12456075182002052900000). If scan tool does not display UNABLE TO CONNECT TO VEHICLE, go to next step.
3. Record any DTCs and freeze-frame data displayed for system diagnosis. If driveability problem exists and no DTCs are present, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
4. If any DTCs are present, perform appropriate test in «DIAGNOSTIC TESTS»(ref-140773-S27879351892002052900000). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-140773-S34633571942002052900000).
5. After repairs for DTC have been completed, DTCs must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-140773-S02148857992002052900000).

Scheme 23

CIRCUIT TESTS

Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .

Scheme 24

1. Access the ECM, located in engine compartment, near battery. (Scheme 17) Turn ignition switch to ON position. Using a DVOM, measure voltage (backprobe) between terminal OD1 of appropriate ECM harness connector and ground. (Scheme 30) If 10-14 volts is present, substitute known-good ECM and retest. If voltage is not as specified, go to next step.
2. Turn ignition off. Disconnect cruise control ECU harness connector located behind instrument panel, on driver's side of vehicle. Turn ignition on. Measure voltage between terminal O/D and ground. (Scheme 24) If 10-14 volts is present, replace cruise control ECU and retest. If 10-14 volts is not present, check and repair circuit between cruise control ECU and ECM. If circuit is okay, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.

COMPONENT TESTS

Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .

BRAKELIGHT SWITCH

Disconnect electrical connector from brakelight switch located near brake pedal. Using ohmmeter, ensure continuity exists between switch terminals No. 1 and 2 with brake pedal depressed. (Scheme 25) Continuity should exist between terminals No. 3 and 4 (with cruise control) with pedal released. Replace switch if continuity is not as specified.

Scheme 25

OVERDRIVE SWITCH

Disconnect electrical connector from O/D switch located on selector lever. Using a DVOM, ensure continuity exists between terminals No. 5 and 6 on Celica or terminals No. 2 and 4 on ECHO, with switch depressed (ON). (Scheme 26)and (Scheme 27). Ensure no continuity exists with switch released (OFF). Replace switch if defective.

Scheme 26

Scheme 27

PARK/NEUTRAL POSITION SWITCH

Disconnect harness connector at park/neutral position switch. Switch is located on side of transaxle. Using ohmmeter, check for continuity between specified terminals in accordance with selector lever position. See PNP SWITCH CONTINUITY table. Replace PNP switch if continuity is not as specified. If switch is okay, check and repair wiring harness or connector between PNP switch and ECM.

PNP SWITCH CONTINUITY

Note. The following information can also be used to diagnose DTC P0770. For testing of shift solenoid SLT, see DTC P1760: SHIFT SOLENOID SLT CIRCUIT under DIAGNOSTIC TESTS.

1. Raise and support vehicle. Remove transaxle oil pan. See LUBRICATION in appropriate SERVICING article. Remove shift solenoid SL. (Scheme 20) Connect battery voltage to solenoid. Apply 71 psi (5 kg/cm 2 ) of compressed air to solenoid with battery voltage connected. (Scheme 28)
2. With battery voltage applied, air should pass through solenoid. Disconnect voltage to solenoid. Ensure air does not pass through solenoid. Replace solenoid as necessary.
3. Using a DVOM, measure resistance between solenoid body and solenoid connector terminal. Resistance should be 11-15 ohms. Replace solenoid as necessary.

Note. For testing of shift solenoid SLT, see DTC P1760: SHIFT SOLENOID SLT CIRCUIT under DIAGNOSTIC TESTS.

Scheme 28

1. Raise and support vehicle. Remove transaxle oil pan. See LUBRICATION in appropriate SERVICING article. To check solenoid seals, remove suspect solenoid. Connect battery voltage to solenoid. Apply 71 psi (5 kg/cm 2 ) of compressed air to solenoid with battery voltage connected.
2. With battery voltage applied, air should pass through solenoid. Disconnect voltage to solenoid. Ensure air does not pass through solenoid. (Scheme 28) Replace solenoid if necessary.
3. Using a DVOM, measure resistance between solenoid body and solenoid connector terminal. Resistance should be 11-15 ohms. Replace solenoid as necessary.

Scheme 29

1. Remove speed sensor from transaxle. Using a DVOM, measure resistance between sensor terminals. Resistance should be 560-680 ohms. If resistance is not as specified, replace sensor. If resistance is as specified, check and repair circuits between sensor and ECM.
2. Check voltage between sensor terminals when a magnet is put close to tip of speed sensor. (Scheme 29) If a low intermittent voltage is generated, sensor is okay. If no voltage is generated, replace speed sensor.

Note. Brakelight switch may also be referred to as stoplight switch.

ECM PIN VOLTAGES

Access the ECM, located in engine compartment, near battery on Celica, and behind glove compartment on ECHO. (Scheme 17)and (Scheme 18). Turn ignition switch to ON position. Using a DVOM, backprobe appropriate ECM harness connector. Check voltage between selected terminals. (Scheme 30)and (Scheme 31). Voltage should be as specified.

Scheme 30

Scheme 31

Transaxle Electronic Control System Wiring Diagram (2001-02 Celica). Scheme 32

Transaxle Electronic Control System Wiring Diagram (2001-02 ECHO). Scheme 33