Component Tests and General Diagnostics

Differential Locking System:

1. Inspect differential lock system.
a. Inspect the indicator lights Check that the indicator lights (front side and rear side) light up for approx. 1 second when the ignition switch is turned ON.





b. Inspect the differential lock operation.
(1) Jack up the vehicle then start the engine.
(2) Put the transfer shift lever on the L position.
(3) When the Differential. Lock control switch is set to the RR position, the indicator light (rear side) is turned on. Differential lock is applied to the rear wheel at this time.

HINT: If the gears of the differential lock system are not meshed, the indicator light remains blinking, so rotate the tires to mesh the gear.





(4) When the Differential. lock control switch is at the OFF position, the indicator light goes off. Differential lock is released for the rear wheel at this time.





(5) When the Differential. Lock control switch is set to the FR/RR position, the indicator lights (front side and rear side) are turned on. Differential lock is applied to both the front wheels and rear wheels at this time.





(6) Check the voltage between the terminals of the Differential. Lock ECU when switching the Differential. Lock control switch with the speedometer, registering approx. 8 km/in (5 MPH) or more.





(7) Check that the indicator lights blink when center Differential. Lock release mode is set. Differential. Lock is released for both the front wheels and rear wheels at this time.
(8) Return the Differential. Lock control switch to OFF.
(9) Stop the engine and lower the vehicle.

Differential Lock System Circuit Chart:

2. Inspect Differential. Lock system circuit.
a. Inspect the system circuit with connector disconnected. Disconnect the connector from the Differential. lock ECU and inspect the connector on the wire harness side, as shown in the chart.

HINT: When a signal enters the ECU to LOCK the front differential and set the rear differential to FREE (when battery positive voltage is inputted to terminal 6 (RF) of ECU and about 0 V is inputted to terminal 12 (R)), or a signal to FREE both the front and rear differentials, the indicator lights keep blinking until the ignition switch is turned off (Fail-safe function). If the circuit is not as specified, check and repair or replace the trouble part shown in the table.

b. Inspect the battery positive voltage Battery positive voltage: 1 - 14.5 V
c. Inspect the system circuit with connector connected.
(1) Turn the ignition switch to the ON position.
(2) Keep the center Differential. Lock condition.
(3) Remove the Differential. Lock ECU.








(4) Using a voltmeter, measure the voltage when the differential lock control switch is in the position, as shown below.
^ If the circuit is not as specified, replace the ECU.

(5) Install the ECU in place.








3. Inspect Differential. Lock actuator.
a. Jack up the vehicle.
b. Use the heater main relay and connect it.

NOTICE:Connect the terminals being careful not to touch the neighboring terminals or metallic parts of relay housing.

c. Rotate the tire and check that differential lock has occurred.
^ If operation is not as specified, replace the actuator.








4. Inspect Differential. Lock control switch.
Inspect the switch continuity between terminals, as shown.
If continuity is not as specified, replace the switch.





5. Inspect Differential. Lock position switch.
a. Inspect the Differential. Lock position switch (Front and Rear):
(1) Check that there is continuity between terminals when the switch is pushed (differential connected position).
(2) Check that there is no continuity when the switch is free (differential disconnected position).
^ If operation is not as specified, replace the switch.

b. Inspect the center cliff. indicator switch.

6. Inspect vehicle speed sensor and indicator light.
a. Inspect the vehicle speed sensor.
b. Inspect the indicator light.