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 Controller Area Network, Trouble code diagnosis).

DTC SET CONDITION
WCM receives the wheel speed information from ASC-ECU via the CAN-bus line.Although WCM 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 WCM
- 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. M.U.T.-III CAN bus diagnostics

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 (Refer to Controller Area Network - CAN Bus Diagnostics table). 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 Active Skid Control System (ASC), diagnostic trouble code chart).

Q: Is the check result normal?

YES: Go to Step 4.

NO: Carry out the troubleshooting for ASC-ECU (Refer to Active Skid Control System (ASC), diagnostic trouble code chart). 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 Chassis Electrical, ETACS - diagnostic trouble code chart).

Q: Is the check result normal?

YES: Go to Step 5.

NO: Troubleshoot the set DTC (Refer to Chassis Electrical, ETACS - diagnostic trouble code chart). Then go to Step 6.

STEP 5. Check the TPMS transmitter acceleration.

Check the acceleration value of each TPMS transmitter by the TPMS transmitter check function (Refer to ID Codes Registration Procedure).

OK: Acceleration value: 5G or less

Q: Is the check result OK?

YES: Replace the WCM and register ID codes (Refer to ID Codes Registration Judgment Table). Then go to Step 6.

NO: Replace the TPMS transmitter and register ID codes (Refer to ID Codes Registration Judgment Table). 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.