Wireless Control Module (WCM)

DTC C1901: Vehicle Speed Information Abnormality

CAUTION: If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to Trouble code diagnosis). Can Bus Diagnostics Table

DTC SET CONDITION
KOS-ECU receives the wheel speed information from ASC-ECU via the CAN-bus line. Although KOS-ECU receives the information that the wheel is not currently rotated from ASC-ECU, if the TPMS transmitter sends the information that the wheel is rotated, this code is set.

TROUBLESHOOTING HINTS
The most likely causes for this DTC to set are:
- Damaged wiring harness and connector
- Malfunction of TPMS transmitter
- Malfunction of KOS-ECU
- Malfunction of ASC-ECU
- Malfunction of ETACS-ECU

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.

Use scan tool to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : Go to Step 3.

NO : Repair the CAN bus lines. On completion, go to Step 2.

STEP 2. Diagnostic trouble code recheck after resetting CAN bus lines

1. Turn the ignition switch to the "LOCK" (OFF) position.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC C1901 set?

YES : Go to Step 3.

NO : The procedure is complete.

STEP 3. Check for other diagnostic trouble code.

Check if the diagnostic trouble code is set from ASC-ECU (Refer to diagnostic trouble code chart). Diagnostic Trouble Code Descriptions

Q: Is the check result normal?

YES : Go to Step 4.

NO : Carry out the troubleshooting for ASC-ECU (Refer to diagnostic trouble code chart). Diagnostic Trouble Code Descriptions Then go to Step 6.

STEP 4. Check for other diagnostic trouble code.

Check if the diagnostic trouble code is set from ETACS-ECU (Refer to ETACS - diagnostic trouble code chart). Diagnostic Trouble Code Descriptions

Q: Is the check result normal?

YES : Go to Step 5.

NO : Troubleshoot the set DTC (Refer to ETACS - diagnostic trouble code chart). Diagnostic Trouble Code Descriptions Then go to Step 6.

STEP 5. Check the TPMS transmitter acceleration.

Check the acceleration value of each TPMS transmitter by the air pressure of data list. Data List Reference Table

OK: Acceleration value: 5G or less

Q: Is the check result OK?

YES : Replace the WCM and register ID codes. Then go to Step 6.

NO : Replace the TPMS transmitter and register ID codes. Then go to Step 6.

STEP 6. Recheck for diagnostic trouble code.

1. Turn the ignition switch to the "LOCK" (OFF) position.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC C1901 set?

YES : Start over at Step 1.

NO : The procedure is complete.