Inspection of Electronic Control Components

ELECTRONIC CONTROL CIRCUIT

ELECTRONIC CONTROL COMPONENTS

TROUBLESHOOTING FLOW-CHARTS

Trouble No.1: No Shifting

Trouble No.2: Shift Point Too High Or Too Low

Trouble No.3 No Up-shift To Overdrive (After Warm-up)

Trouble No.4 No Lock-up (After Warm-up)

INSPECTION OF T(T) TERMINAL VOLTAGE

1. INSPECT THROTTLE POSITION SENSOR SIGNAL
a. Turn the ignition switch to ON. Do not start the engine.

b. Connect a voltmeter to terminals T(T) and E(1).

c. While slowly depressing the accelerator pedal, check that T(T) terminal voltage rises in sequence.
If the voltage does not change in proportion to the throttle opening angle, there is a malfunction in the throttle position sensor or circuit.

2. INSPECT BRAKE SIGNAL
a. Depress the accelerator pedal until the T(T) terminal indicates 8 V.
b. Depress the brake pedal and check the voltage reading from the or T(T) terminal.

Brake pedal depressed: 0 V
Brake pedal released: 8 V

If not as indicated, there is a malfunction in either the stop light switch or circuit.

3. INSPECT EACH UP-SHIFT POSITION
a. Warm up the engine.

Coolant temperature: 176°F (80°C)

b. Turn the O/D switch to "ON".
c. Place the pattern select switch in "Normal" and the shift lever into the D range.
d. During a road test (above 10 km/h or 6 mph) check that voltage at the T(T) terminal is as indicated below for each up-shift position.

If the voltage rises from 0 V to 7 V in the sequence shown, the control system is okay.
The chart above shows the voltmeter reading and corresponding gears.

NOTE: Determine the gear position by a light shock or change in engine rpm when shifting. The lock-up clutch will turn ON only infrequently during normal 2nd and 3rd gear operation. To trigger this action, press the accelerator pedal to 50% or more of its stroke. At less than 50%, the voltage may change in the sequence 2 V - 4 V - 6 V - 7 V.

INSPECTION OF ELECTRONIC CONTROL COMPONENTS

1. INSPECT VOLTAGE OF TCCS ECU CONNECTOR

TCCS ECU Pinout Values:

a. Turn on the ignition switch.
b. Measure the voltage at each terminal.

2. INSPECT VOLTAGE OF ECT ECU CONNECTOR

ECT ECU Pinout Values:

a. Turn on the ignition switch.
b. Measure the voltage at each terminal.

3. INSPECT SOLENOID VALVES

a. Disconnect the connector from ECT ECU.
b. Measure the resistance between S(1), S(2), S(L) and body ground.

Resistance: 11 - 15 ohm

c. Apply battery voltage to each terminal.
Check that an operation noise can be heard from the solenoid.

4. INSPECT CENTER DIFFERENTIAL CONTROL SOLENOID VALVES

a. Disconnect the connector from ECT ECU.
b. Measure the resistance between SD(1), SD(2) and body ground.

Resistance: 11 - 15 ohm

c. Apply battery voltage to each terminal.
Check that an operation noise can be heard from the solenoid.

5. CHECK SOLENOID SEALS
If there is foreign material in the solenoid valve, there will be no fluid control even with solenoid operation.

a. Check No. 1 and No. 2 solenoid valves.
- Applying 5 kg/Sq. cm (71 psi, 490 kPa) of compressed air, check that the solenoid valves open do not leak the air.
- When supply battery voltage to the solenoids, check that the solenoid valves open.

b. Check the lock-up solenoid valve.

- Applying 5 kg/Sq. cm (71 psi, 490 kPa) of compressed air, check that the solenoid valve opens.
- When supply battery voltage to the solenoid, check that the solenoid valve does not leak the air.

c. Check No. 1 and No. 2 center differential control solenoid valves.

- Applying 5 kg/Sq. cm (71 psi, 490 kPa) of compressed air, check that the solenoid valves open do not leak the air.
- When supply battery voltage to the solenoids, check that the solenoid valves open.

6. INSPECT NEUTRAL START SWITCH

Using an ohmmeter, check the continuity of the terminals for each switch position shown in the table below.

7. INSPECT THROTTLE POSITION SENSOR

Using an ohmmeter, check the resistance between each terminal.

8. INSPECT VEHICLE SPEED SENSOR AND REAR WHEEL SPEED SENSOR
a. Disconnect the connector from ECT ECU.

b. Measure the resistance between FR and FR+ (vehicle speed sensor), and between RR and RR+ (rear wheel speed sensor).
Resistance: 620 ± 60 ohm

9. INSPECT PATTERN SELECTION SWITCH

Inspect that there is continuity between 5 and each terminal.

NOTE: As there are diodes inside, be careful of the tester probe polarity.

10. INSPECT O/D MAIN SWITCH

Inspect that there is continuity between terminals 1 and 3.

11. INSPECT CENTER DIFFERENTIAL CONTROL SWITCH

a. Disconnect the connector from center differential control switch.
b. Inspect that there is continuity between terminals 1 and 4.