ENGINE CONTROL MODULE
ECM receives information from various input devices and uses this information to control shift solenoids on transmission valve body for transmission shifting and lock-up solenoid (also called SLU solenoid) for torque converter lock-up. ECM contains a self-diagnostic system, which will store Diagnostic Trouble Codes (DTC) if a failure or problem exists in electronic control system. Trouble codes can be retrieved to determine problem area. See SELF DIAGNOSTIC SYSTEM. For ECM locations (Scheme 20)- (Scheme 24).
ATF Temperature Sensor
Sensor delivers an input signal to ECM to indicate fluid temperature. Sensor converts fluid temperature into a resistance value. Sensor is connected to internal transmission wiring harness.
Stop Light Switch Signal
Stop light switch delivers input signal to ECM, indicating vehicle braking. Stop light switch is located on brake pedal support.
Cruise Control Electronic Control Unit
Cruise control ECU delivers an input signal to control overdrive operation in accordance with vehicle speed when cruise control is operating.
Engine Coolant Temperature Sensor Signal
Coolant temperature sensor delivers input signal to ECM, indicating engine coolant temperature. Engine coolant temperature sensor is located at top left or right front of engine, near thermostat housing.
O/D Direct Clutch Speed Sensor Signal
Sensor delivers input signal to ECM, indicating O/D input shaft RPM. By comparing O/D direct clutch drum signal and vehicle speed sensor signal, ECM detects shift timing of gears and controls engine torque and hydraulic pressure in response to various conditions. Sensor is located on left side of transmission, near torque converter housing.
Park/Neutral Position Switch Signal
PNP switch delivers an input signal to ECM indicating gearshift lever position. Switch is located on side of transmission.
Pattern Select Switch Signal
Pattern select switch delivers an input signal to ECM to indicate transmission shift points selected by vehicle operator. Pattern select switch is located near the gearshift lever on center console. (Scheme 20)- (Scheme 24).
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
Vehicle speed sensor signal is delivered to ECM by VSS. VSS detects transmission output shaft speed. Gear shift point and lock-up timing are controlled by ECM based on signals from vehicle speed sensor and throttle position sensor.
Scheme 20
Scheme 21
Scheme 22
Scheme 23
Scheme 24
ECM OUTPUT DEVICES
Note. In some gears, ECM provides a fail-safe system which will place transmission in designated gear depending on solenoid failure.
No. 1, No. 2, No. 3 & No. 4 Solenoids
ECM controls transmission shifting by delivering an output signal to operate proper solenoid. Solenoids are located on transmission valve body. see scheme 3 Solenoids are operated in accordance with gearshift lever position. If a solenoid malfunctions, fail-safe gear may be selected. (Scheme 25)
SLU Solenoid
ECM controls torque converter lock-up by delivering an output signal to lock-up solenoid. Lock-up solenoid (also called SLU solenoid) is activated when the gearshift lever is in "D" position and vehicle is at specified speed. Lock-up solenoid is located on transmission valve body.
SLN Solenoid
SLN solenoid controls hydraulic pressure acting on accumulator control valve when transmission shifts and assists in smooth shifting. ECM determines optimum control pressure according to signals from TP sensor, vehicle speed sensor and direct clutch drum speed sensor, and controls volume of current flow to SLN solenoid. Amount of current flow to SLN solenoid is controlled by duty cycle ratio of ECM output signal, causing a momentary change in hydraulic pressure acting on clutches during shifting. When duty cycle ratio is high, pressure is low. SLN solenoid is located on transmission valve body. (Scheme 25)
Scheme 25
Delayed 1-2, 2-3 Or 3-O/D Upshifts, Or Downshifts From O/D-3 Or 3-2, Then Changes Back To O/D Or 3rd
Faulty valve body, ECM or solenoid valve.
Downshifts Early Or Late When Coasting
Faulty valve body, solenoid valve or ECM.
Drag Or Binding On Upshifts
Shift linkage out of adjustment or faulty valve body.
Engine Stalls When Starting Off Or Stopping
Faulty torque converter.
Harsh Downshift
Accumulator pistons, valve body or ECM faulty.
Harsh Engagement Into Any Drive Range
Faulty valve body, primary regulator or accumulator pistons. Faulty O/D brake, O/D direct clutch, O/D planetary gear unit or torque converter. Faulty 1st and reverse brake, direct clutch or forward clutch.
No Downshift When Coasting
Faulty valve body, solenoid valve or ECM.
No Downshift 2-1
Faulty 3rd coast brake or faulty 2nd brake.
No Engine Braking 1st-3rd
Faulty O/D direct clutch, 1st and reverse brake or 3rd coast brake.
No Engine Braking In "2" Or "L" Range
Faulty valve body, solenoid valve or ECM.
No Lock-Up Or No Lock-Up Off
Faulty torque converter or solenoid.
No Lock-Up In 2nd, 3rd Or O/D
Faulty valve body, solenoid valve or ECM.
No Movement In Any Gear
Shift linkage out of adjustment. Faulty valve body or primary regulator. Parking lock pawl faulty. Faulty torque converter. Converter drive plate damaged or broken. Oil pump intake screen blocked. ECM faulty. Control shaft lever out of adjustment. Faulty O/D one-way clutch, O/D brake, O/D direct clutch or O/D planetary gear.
No O/D-4, O/D-3, 3-2 Or 2-1 Kickdown
Faulty valve body, solenoid valve or ECM.
No Upshift 1-2, 2-3, 3-O/D, 3-4, 4-O/D
Faulty 2nd brake or No. 1 one-way clutch. Faulty direct clutch. Faulty O/D brake.
Poor Acceleration
Faulty torque converter, O/D direct clutch, O/D planetary gear unit or O/D brake. Faulty 3rd coast brake, direct clutch, 2nd brake or 1st and reverse brake. Faulty forward clutch.
Selector Lever Position Incorrect
Shift linkage out of adjustment. Faulty manual valve and lever.
Slips On Any Upshift Or Slips Or Shudders On Acceleration
Shift linkage out of adjustment. Faulty valve body or solenoid valve.
Slip Or Shudder In "D", "R", 1st, 2nd, 3rd, 4th Or O/D
Faulty torque converter, O/D one-way clutch or O/D direct clutch. Faulty 1st and reverse brake or direct clutch. Faulty forward clutch or No. 2 one-way clutch. Faulty 2nd brake, 3rd coast brake or No. 1 one-way clutch. Faulty O/D brake.
Vehicle Does Not Hold In "P" Range
Shift linkage faulty or out of adjustment. Defective parking lock pawl assembly.
Vehicle Does Not Move In "D", "2" Or "L" Range
Faulty forward clutch. Faulty No. 2 one-way clutch. Faulty 1st and reverse brake. Faulty 3rd coast brake, direct clutch or 2nd brake.
Vehicle Does Not Move In "R" Range
Faulty 3rd coast brake, front and rear planetary gear unit or direct clutch. Faulty 1st and reverse brake. Faulty O/D direct clutch.
HYDRAULIC PRESSURE TESTS
Note. Hydraulic pressure test should be performed with transmission fluid temperature at 122-176°F (50-80°C).
- Ensure transmission fluid is at normal operating temperature. Remove plug from left side of transmission case, next to 3rd coast brake servo cover and install appropriate pressure gauge. (Scheme 26)
- Apply parking and service brakes. Start engine. Ensure idle speed is within manufacturer's specifications. Place transmission in "D" range.
- Check main line pressure at engine idle. Repeat procedure in "R" range. Compare all readings to specification. See «LINE PRESSURE SPECIFICATIONS»(ref-140961-S25497654312001072700000) table.
- Check main line pressure at full throttle (stall speed). Read highest pressure when engine reaches stall speed. Repeat procedure in "R" range. Compare all readings to specification.
Scheme 26
NORMAL Mode Code Retrieval
- Connect scan tool to Data Link Connector (DLC3). (Scheme 27) DLC3 is located under left side of instrument panel. Turn ignition on, engine off. Turn scan tool on. Using scan tool manufacturer's instructions, check for DTCs and freeze-frame data.
- If scan tool displays UNABLE TO CONNECT TO VEHICLE, DLC3 must be checked. See «DLC3 INSPECTION»(ref-140961-S10922429942002061000000) under SCAN TOOL PROBLEMS. If scan tool does not display UNABLE TO CONNECT TO VEHICLE, go to next step.
- 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.
- If any DTCs are present, perform appropriate test under «DIAGNOSTIC TESTS»(ref-140961-S40642277862002061000000). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-140961-S39848087492002070200000).
- After repairs for DTC have been completed, DTCs must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-140961-S16684393182002061000000).
Scheme 27
SUMMARY
Note. Always clear DTCs once repairs are complete. See CLEARING DIAGNOSTIC TROUBLE CODES . Road test vehicle and retrieve DTCs to determine if complaint or DTC is repaired.
If no hard DTCs are present, and driveability symptoms or intermittent DTCs exist, attempt diagnosis by symptom, or by testing individual components related to system fault. See SYMPTOM DIAGNOSIS TROUBLE SHOOTING and/or COMPONENT TESTS . If no problem is found, verify proper electronic control system circuit operation. See PIN VOLTAGE TESTS .
Note. To access all solenoids, see LUBRICATION in appropriate SERVICING article.
Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .
- To check solenoid seals, remove suspect solenoid. Connect battery voltage to solenoid. Apply 71 psi (5 kg/cm 2 ) to solenoid with battery voltage connected.
- With battery voltage applied, air should pass through solenoid. Disconnect voltage to solenoid. Ensure air does not pass through solenoid. Replace solenoid if defective.
- Using ohmmeter, measure resistance between case and solenoid connector terminal. Resistance should be 11-15 ohms. Replace solenoid as necessary.
O/D DIRECT & VEHICLE SPEED SENSOR
Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .
- Remove speed sensor from transmission. Using 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, go to next step.
- Check voltage between sensor terminals when a magnet is put close to tip of speed sensor. see scheme 13 If a low intermittent voltage is generated, sensor is okay. Check and repair circuits between sensor and ECM. If no voltage is generated, replace speed sensor.
PARK/NEUTRAL POSITION SWITCH
Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .
Disconnect harness connector at park/neutral position switch. Switch is located on side of transmission. Using ohmmeter, check for continuity between specified terminals in accordance with the gearshift lever position. For GS 300 and GS 430, see PNP SWITCH CONTINUITY (GS 300 & GS 430) table and see scheme 24. For IS 300, LS 430 and SC 430 (Scheme 28) On all models, replace PNP switch if defective.
| Selector Lever Position | Continuity @ Terminals No. |
|---|---|
| "P" | 1 & 3; 6 & 9 |
| "R" | 2 & 3 |
| "N" | 3 & 5; 6 & 9 |
| "D" 4, Or "M" | 3 & 7 |
| "2" | 3 & 4 |
| "L" | 3 & 8 |
PNP SWITCH CONTINUITY (GS 300 & GS 430)
Scheme 28
PATTERN SELECT SWITCH
Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .
Disconnect pattern select switch connector. Using ohmmeter, check continuity between specified terminals. See PATTERN SELECT SWITCH CONTINUITY table. Replace switch as necessary.
| Switch Position | Terminals No. | Continuity | |
|---|---|---|---|
| GS 300 & GS 430 (1) | |||
| PWR | 3 & 7 | Yes | |
| NORM | 1 & 3; 3 & 7 | No | |
| SNOW | 1 & 3 | Yes | |
| IS 300 (2) | |||
| PWR | 1 & 6 | Yes | |
| NORM | 1 & 3; 1 & 6 | No | |
| SNOW | 1 & 3 | Yes | |
| LS 430 (3) | |||
| PWR | 1 & 6 | Yes | |
| NORM | 1 & 3 & 1 & 6 | No | |
| SNOW | 1 & 3 | Yes | |
| SC 430 (3) | |||
| PWR | 1 & 6 | Yes | |
| NORM | 1 & 3; 1 & 6 | No | |
| SNOW | 1 & 3 | Yes | |
| (1) see scheme 20 (2) see scheme 28 (3) see scheme 27 | |||
| (1) | See scheme 20 |
| (2) | See scheme 28 |
| (3) | See scheme 27 |
PATTERN SELECT SWITCH CONTINUITY
Scheme 29
SLN, SLT & SLU SOLENOID
Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .
Raise and support vehicle. Remove transmission oil pan. See LUBRICATION in appropriate SERVICING article. Remove appropriate solenoid. see scheme 3 To check solenoid operation, connect positive battery voltage to solenoid terminal No. 1. Ensure an 8-10-watt bulb is placed in-line of positive lead. see scheme 15 Connect ground to terminal No. 2 and monitor valve's movement. Replace as necessary.
TRANSMISSION CONTROL SWITCH
Note. For circuit reference, see WIRING DIAGRAMS and/or CONNECTOR IDENTIFICATION .
Disconnect transmission control switch connector. Using ohmmeter, check continuity between specified terminals. See TRANSMISSION CONTROL SWITCH CONTINUITY table. Replace switch as necessary.
| Selector Lever Position | Terminals No. | Continuity | |
|---|---|---|---|
| GS 300 & GS 430 (1) | |||
| "D" | 10 & 2 | No | |
| "4" | 10 & 2 | Yes | |
| "2" | 9 & 5 | No | |
| "L" | 9 & 5 | Yes | |
| IS 300 (2) | |||
| "P" | 1 & 6 | No | |
| "M" | 1 & 6 | Yes | |
| "2" | 4 & 5 | No | |
| "L" | 4 & 5 | Yes | |
| LS 430 & SC 430 (3) | |||
| "D" | 2 & 10 | No | |
| "4" | 2 & 10 | Yes | |
| "2" | 3 & 6 | No | |
| "L" | 3 & 6 | Yes | |
| (1) see scheme 27 (2) see scheme 28 (3) see scheme 29 | |||
| (1) | See scheme 27 |
| (2) | See scheme 28 |
| (3) | See scheme 29 |
TRANSMISSION CONTROL SWITCH CONTINUITY
| CAUTION | If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. |
Note. Wipe any water off on the ECM cover and the circumference. Procedure should be done indoors where it is dry. Do not put any water into the inside of the engine control module (connector part or screw part). When exchanging ECM, check that there is no trash and foreign objects stuck in the ECM box side (adhesive side).
PIN VOLTAGE TESTS
Note. In the following pin voltage tables, the letter "L" under wiring color represents the color Blue.
Access ECM. See ENGINE CONTROL MODULE under REMOVAL & INSTALLATION. Turn ignition on. Using voltmeter, measure voltage at ECM harness connector. Check voltage between selected terminal and terminal E1 (ground). Voltage should be as specified in pin voltage tables. (Scheme 30)- (Scheme 37).
