If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Diagnose the CAN bus lines before the diagnosis codes (Refer to GROUP 54C, CAN bus-line diagnostic flow ).
Whenever the ECU is replaced, ensure that the communication circuit is normal.
OPERATION
ASTC-ECU detects the rear differential lock operation status by the following information.
Rear differential lock detection switch: ON
Rear differential lock indicator lamp: illuminates or flashes
If these signals become effective, it is judged that the rear differential lock is activated and ABS (EBD)/ASC/TCL control is prohibited. The ASTC indicator lamp, the ASTC OFF indicator lamp, the ABS warning lamp, and brake warning lamp illuminate at the same time.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set in the following cases.
Rear differential lock engage switch: ON, Rear differential lock indicator signal: When the OFF signal is received for a certain period at the same time
Rear differential lock engage switch: OFF, Rear differential lock indicator signal: When the ON signal is received for a certain period at the same time
PROBABLE CAUSES
Damaged wiring harness or connector
Malfunction of rear differential lock detection switch
Malfunction of rear differential lock-ECU
Malfunction of ASTC-ECU
DIAGNOSIS
STEP 1. M.U.T.-III CAN bus diagnosis
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, CAN bus line Diagnostic flow ). Then go to Step 2.
STEP 2. Check whether the diagnosis code is reset.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Start the engine.
(6)Drive the vehicle more than 10 seconds at the speed exceeds 10 km/h.
(7)Check if the diagnosis code is set.
Q.
Is code No.C1293 set?
Go to Step 3.
The procedure is complete.
STEP 3. Check the M.U.T.-III data list.
(1)Turn the ignition switch to the "ON" position.
(2)Operate the rear differential lock switch, and check if the operation status matches the service data output.
Item No.63: Rear differential lock switch
OK:
(Rear differential lock switch: ON): ON (Rear differential lock switch: OFF): OFF
Replace the Rear differential lock detection switch (Refer to GROUP 27 - Rear differential lock ). Then go to Step 16.
STEP 6. Rear differential lock-ECU check
Refer to GROUP 27 - Rear differential lock-ECU .
Q.
Is the check result normal?
Go to Step 7.
Replace the Rear differential lock-ECU (Refer to GROUP 27 - Rear differential lock-ECU ). Then go to Step 16.
STEP 7. Resistance measurement at the C-23 rear differential lock-ECU connector
(1)Disconnect the C-23 rear differential lock-ECU connector and measure the resistance at the harness side.
(2)Disconnect the A-68 ASTC-ECU connector.
(3)Measure the resistance between the C-23 rear differential lock-ECU connector terminal No.10 and body earth. OK: No continuity
Q.
Is the check result normal?
Go to Step 8.
Repair the wiring harness. Then go to Step 16.
STEP 8. Voltage measurement at the C-23 rear differential lock-ECU connector
(1)Disconnect the C-23 rear differential lock-ECU connector and measure the voltage at the harness side.
(2)Disconnect the A-68 ASTC-ECU connector.
(3)Measure the voltage between the C-23 rear differential lock-ECU connector terminal No.10 and body earth. OK: 1 V or less
Q.
Is the check result normal?
Go to Step 9.
Repair the wiring harness. Then go to Step 16.
STEP 9. Resistance measurement at the A-68 ASTC-ECU connector and C-23 rear differential lock-ECU connector
(1)Disconnect the connector A-68, and connect special tool ASC check harness (MB992159) to the wiring harness-side connector.
note
Do not connect special tool ASC check harness (MB992159) to the ASTC-ECU.
(2)Disconnect the C-23 rear differential lock-ECU connector. (3)Measure the resistance between the A-68 ASTC-ECU connector terminal No.41 and C-23 rear differential lock-ECU connector terminal No.10. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 10.
Repair the wiring harness. Then go to Step 16.
STEP 10. Resistance measurement at the C-23 rear differential lock-ECU connector
(1)Disconnect the C-23 rear differential lock-ECU connector and measure the resistance at the harness side.
(2)Disconnect the A-68 ASTC-ECU connector and D-22-1 rear differential lock detection switch connector.
(3)Measure the resistance between the C-23 rear differential lock-ECU connector terminal No.8 and body earth. OK: No continuity
Q.
Is the check result normal?
Go to Step 11.
Repair the wiring harness. Then go to Step 16.
STEP 11. Resistance measurement at the A-68 ASTC-ECU connector and C-23 rear differential lock-ECU connector
(1)Disconnect the connector A-68, and connect special tool ASC check harness (MB992159) to the wiring harness-side connector.
note
Do not connect special tool ASC check harness (MB992159) to the ASTC-ECU.
(2)Disconnect the C-23 rear differential lock-ECU connector. (3)Measure the resistance between the A-68 ASTC-ECU connector terminal No.19 and C-23 rear differential lock-ECU connector terminal No.8. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 12.
Repair the wiring harness. Then go to Step 16.
STEP 12. Resistance measurement at the A-68 ASTC-ECU connector and D-22-1 rear differential lock detection switch connector
(1)Disconnect the connector A-68, and connect special tool ASC check harness (MB992159) to the wiring harness-side connector.
note
Do not connect special tool ASC check harness (MB992159) to the ASTC-ECU.
(2)Disconnect the D-22-1 rear differential detection switch connector. (3)Measure the resistance between the A-68 ASTC-ECU connector terminal No.19 and D-22-1 rear differential detection switch connector terminal No.2. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 13.
Repair the wiring harness. Then go to Step 16.
STEP 13. Resistance measurement at the D-22-1 rear differential lock detection switch connector
(1)Disconnect the D-22-1 rear differential lock detection switch connector and measure the resistance at the harness side.
(2)Measure the resistance between the D-22-1 rear differential lock detection switch connector terminal No.1 and body earth. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 14.
Repair the wiring harness. Then go to Step 16.
STEP 14. Check whether the diagnosis code is reset.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Start the engine.
(6)Drive the vehicle more than 10 seconds at the speed exceeds 10 km/h.
(7)Check if the diagnosis code is set.
Q.
Is code No.C1292 set?
Replace the Rear differential lock-ECU (Refer to GROUP 27 - Rear differential lock-ECU ). Then go to Step 15.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
STEP 15. Check whether the diagnosis code is reset.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Start the engine.
(6)Drive the vehicle more than 10 seconds at the speed exceeds 10 km/h.
(7)Check if the diagnosis code is set.
Q.
Is code No.C1292 set?
Replace the ASTC-ECU (Refer to ). Then go to Step 16.
This diagnosis is complete.
STEP 16. Check whether the diagnosis code is reset.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Start the engine.
(6)Drive the vehicle more than 10 seconds at the speed exceeds 10 km/h.
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Go to Step 3.
Repair the CAN bus line (Refer to GROUP 54C, CAN bus line Diagnostic flow 
). Then go to Step 2.)
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