Code No. C1456: Wiring harness or coupling coil overcurrent failure

caution

If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus lines.

OPERATION

The current flowing the coupling coil is monitored, and if it exceeds the specified value, the system is deactivated.

DIAGNOSIS CODE SET CONDITIONS

If the following conditions are met when the system is in operation (always), 4WD-ECU switches the control from 4WD to 2WD, flashes the 4WD/LOCK indicators alternately, and sets the diagnosis code No. C1456.

Electronic control coupling solenoid current monitor value: 6 A or more (deviated from the normal current value range)

PROBABLE CAUSES

Current trouble

Damaged harness wires and connector (Short to earth between 4WD-ECU and the electronic control coupling solenoid)
4WD-ECU internal error
Short circuit in the coupling coil

Past trouble

Intermittent wiring harness or connector failure

note For diagnosis procedures, refer to "How to treat past trouble". (Refer to GROUP 00, How to Treat Past Trouble .)
Intermittent electronic control coupling failure (solenoid failure)

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics

Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 3.

	Repair the CAN bus line. (Refer to GROUP 54C - Troubleshooting .) On completion, go to Step 2.

STEP 2. Check whether the diagnosis code is reset after repairing the CAN bus line.

(1)Erase the diagnosis code.

(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.

(3)Use M.U.T.-III to activate the electronic control coupling to the maximum 4WD control torque. (Refer to Actuator Test Table

(4)Check if the diagnosis code is set.

Q. Is the diagnosis code No. C1456 set?

	Go to Step 3.

	This diagnosis is complete.

STEP 3. M.U.T.-III data list

Check the following service data. (Refer to

Item 04: Coupling current command value
Item 05: Coupling current monitor value

Q. Is the check result normal?

	Replace 4WD-ECU. (Refer to .)

	Go to Step 4.

STEP 4. Check the following connector:

Check the connectors below for improper engagement, terminal damage or terminal drawn in the connector case.

C-130 4WD-ECU connector
D-113 electronic control coupling solenoid connector
C-35 intermediate connector

Q. Are the connectors and terminals in good condition?

	Go to Step 5.

	Repair the connector(s) or terminal(s). Then go to Step 10.

STEP 5. Wiring harness check

Check the wiring harness between the C-130 4WD-ECU connector and the D-113 electronic control coupling solenoid connector for damage or other problem.

Q. Is the wiring harness in good condition?

	Go to Step 6.

	Repair damage or other problem in the wiring harness. Then go to Step 10.

STEP 6. Resistance measurement between electronic control coupling solenoid connector terminals

Disconnect the D-113 connector, and measure the resistance value between the connector terminals on the electronic control coupling side.

Standard value: 2.2 - 4.0 Ω

Q. Is the measured resistance value within the standard value range?

	Go to Step 7.

	Replace the electronic control coupling. (Refer to .) Then go to Step 10.

STEP 7. Voltage measurement at the 4WD-ECU connector

(1)Disconnect the C-130 4WD-ECU connector.

(2)Measure the voltage between the C-130 wiring harness side connector terminals No. 3/4 and No. 10.
OK: Battery voltage

Q. Is the check result normal?

	Go to Step 9.

	Go to Step 8.

STEP 8. Wiring harness check

note

Prior to the wiring harness inspection, check the C-315 ETACS-ECU connector, and repair if necessary.

Check the wiring harness between the C-130 4WD-ECU connector (terminal No. 3) and the C-309 ETACS-ECU connector (terminal No. 1) for damage or other problem.

Q. Is the wiring harness in good condition?

	Go to Step 9.

	Repair the wiring harness. Then go to Step 10.

STEP 9. Check whether the diagnosis code is reset.

(1)Erase the diagnosis code.

(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.

(3)Use M.U.T.-III to activate the electronic control coupling to the maximum 4WD control torque. (Refer to Actuator Test Table

(4)Check if the diagnosis code is set.

Q. Is the diagnosis code No. C1456 set?

	Replace 4WD-ECU. (Refer to .) Then go to Step 10.

	The trouble can be an intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)

STEP 10. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. C1456 set?

	Diagnose again from Step 1.

	This diagnosis is complete.