Electronic Control AWD

DTC C1078: Tire with incorrect diameter equipped

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

OPERATION

If the vehicle is driven with a tire with incorrect diameter (high-pressure type spare tire or flat tire) installed to either wheel in the AWD mode, AWD-ECU controls the coupling in high torque. If this is the case, the coupling temperature may rise to cause a seizure.

DTC SET CONDITIONS

If the following conditions are met simultaneously, AWD-ECU gradually reduces the AWD control torque to the specified torque, flashes the AWD/LOCK indicators alternately, and sets the DTC C1078.

- AWD selector switch: AWD/LOCK

- Difference in rotation speed between the front and rear wheels exceeds continuously a specific value.

TROUBLESHOOTING HINTS

Current trouble

- Tire with incorrect diameter (high-pressure type spare tire or flat tire) equipped

- Improper adjusted tire pressure
Past trouble

- Tire with incorrect diameter (high-pressure type spare tire or flat tire) has been installed.

- The tire pressure has been adjusted due to improper tire pressure.

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface

- MB991827: M.U.T.-III USB Cable

- MB991910: M.U.T.-III Main Harness A

STEP 1. Scan tool MB991958 CAN bus diagnostics

Use scan tool MB991958 to diagnose the CAN bus lines.

Q. Is the check result normal?

YES Go to Step 3.
NO Repair the CAN bus line CAN Bus Diagnostics Chart). On completion, go to Step 2.
STEP 2. Check whether the DTC is reset after repairing the CAN bus line.

(1)Erase the DTC.

(2)Drive the vehicle straight with throttle opening angle of approximately 50% or less, and constant vehicle speed of 30 km/h or higher for 20 seconds or longer.

(3)Check if the DTC is set.

Q. Is the DTC C1078 set?

YES Go to Step 3.
NO The procedure is complete.
STEP 3. Tire check

Q. Are all installed wheels and tires same in size?

YES Go to Step 4.
NO Install the same size wheels and tires. Then go to Step 4.
STEP 4. Tire pressure check

Check that the tire pressure of the installed tires agrees with the tire pressure specified on the tire pressure label.

Q. Is the tire pressure normal?

YES Go to Step 6.
NO Adjust the tire pressure. Then go to Step 5.
STEP 5. Check whether the DTC is reset.

Drive the vehicle straight with throttle opening angle of approximately 50% or less, and constant vehicle speed of 30 km/h (18.6 mph) or higher for 20 seconds or longer.

Q. Is the DTC C1078 set?

YES Go to Step 6.
NO This code is set because the tire pressure was improper or a tire with incorrect diameter is installed.
STEP 6. Scan tool MB991958 data list

Check the following data list (Refer to Data List Reference Table).

- Item 16: FL wheel speed sensor

- Item 17: FR wheel speed sensor

- Item 18: RL wheel speed sensor

- Item 19: RR wheel speed sensor

Q. Is the check result normal?

YES Go to Step 7.
NO Troubleshoot the ABS system Anti-Lock Braking System (ABS)[Vehicles with ABS]), the ASC system
Active Stability Control System (ASC) [Vehicles with ASC]). Then go to Step 7.
STEP 7. Check whether the DTC is reset.

Drive the vehicle straight with throttle opening angle of approximately 50% or less, and constant vehicle speed of 30 km/h (18.6 mph) or higher for 20 seconds or longer.

Q. Is the DTC C1078 set?

YES Replace AWD-ECU (Refer to Electronic Control AWD). Then go to Step 8 .
NO The procedure is complete.
STEP 8. Check whether the DTC is reset.

Q. Is the DTC C1078 set?

YES Diagnose again from Step 1.
NO The procedure is complete.