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DTC C1078: Tire with incorrect diameter equipped
 
 
cautionIf there is any problem in the CAN bus lines, an incorrect DTC may be stored. 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 stores 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
STEP 1. Scan tool MB991958 CAN bus diagnostics
Use scan tool MB991958 to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 3.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting/CAN Bus Diagnostics Table ). 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 stored.
Is the DTC C1078 stored?
Go to Step 3.
The procedure is complete.
 
STEP 3. Tire check
Are all installed wheels and tires same in size?
Go to Step 4.
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.
Is the tire pressure normal?
Go to Step 6.
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.
Is DTC C1078 stored?
Go to Step 6.
This code is stored 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 ).
  • Item 16: FL wheel speed sensor
  • Item 17: FR wheel speed sensor
  • Item 18: RL wheel speed sensor
  • Item 19: RR wheel speed sensor
Is the check result normal?
Go to Step 7.
Troubleshoot the ASC system (Refer to GROUP 35C - Troubleshooting/DTC Chart ). 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.
Is DTC C1078 stored?
Replace AWD-ECU (Refer to ). Then go to Step 8 .
The procedure is complete.
 
STEP 8. Check whether the DTC is reset.
Is DTC C1078 stored?
Diagnose again from Step 1.
The procedure is complete.