Inspection Procedure 17: 4LLc operation detection switch system

OPERATION

A battery voltage is applied to the 4LLc operation detection switch output terminal (terminal 1) from the A/T-ECU (terminal 9) via the resistance in the unit.
The 4LLc operation detection switch is grounded through the transfer case to the vehicle body.

COMMENTS ON TROUBLE SYMPTOM

If the transmission shifts to 4th gear when the transfer lever is in the 4L position, the cause is probably a malfunction of the 4LLc operation detection switch.

PROBABLE CAUSES

Malfunction of the 4LLc operation detection switch
Damaged harness wires and connectors
Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Item 31: 4LLc operation detection switch (Refer to data list reference table

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

	Go to Step 2.

STEP 2. Check the 4LLc operation detection switch.

Refer to

Q. Is the check result normal?

	Go to Step 3.

	Replace the 4LLc operation detection switch.

STEP 3. Measure the voltage at 4LLc operation detection switch connector B-05.

(1)Disconnect the connector, and measure the resistance between terminal 1 and earth at the wiring harness side.
(2)Turn the ignition switch to the ON position.
OK: System voltage

Q. Is the check result normal?

Go to Step 4.

Go to Step 5.

STEP 4. M.U.T.-III data list

Item 31: 4LLc operation detection switch (Refer to data list reference table

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

	Replace the A/T-ECU.

STEP 5. Measure the voltage at A/T-ECU connector C-19.

(1)Disconnect 4LLc operation detection switch connector B-05.

(2)Turn the ignition switch to the ON position.

(3)Measure the voltage between A/T-ECU connector C-19 terminal No.9 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 6.

Go to Step 8.

STEP 6. Connector check: B-05 4LLc operation detection switch connector, A-115 and C-29 intermediate connector, C-19 A/T-ECU connector

Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 7.

Repair the defective connector.

STEP 7. Check the harness between 4LLc operation detection switch connector B-05 terminal No.1 and A/T-ECU connector C-19 terminal No.9.

Check the power supply line for open circuit.

Q. Is the check result normal?

Go to Step 4.

Repair the wiring harness.

STEP 8. Connector check: B-05 4LLc operation detection switch connector, A-115 and C-29 intermediate connector, C-19 A/T-ECU connector

Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 9.

Repair the defective connector.

STEP 9. Check the harness between 4LLc operation detection switch connector B-05 terminal No.1 and A/T-ECU connector C-19 terminal No.9.

Check the power supply line for short circuit.

Q. Is the check result normal?

Go to Step 4.

Repair the wiring harness.