Supplemental Restraint System (SRS)

DTC U0154: Occupant Classification-ECU CAN Time-out

CAUTION:

- If the DTC U0154 is set, be sure to diagnose the CAN main bus line.
- When replacing the ECU, always check that the communication circuit is normal.

DIAGNOSTIC FUNCTION

When the signals from occupant classification-ECU cannot be received, the SRS-ECU sets the DTC U0154.

DTC SET CONDITION

Because of the CAN-B bus circuit malfunction, if SRS-ECU becomes unable to perform the normal data transmission, SRS-ECU determines that an abnormality is present.

TROUBLESHOOTING HINTS

- The CAN bus line may be defective
- The occupant classification-ECU may be defective
- The SRS-ECU may be defective

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

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





(1)
CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Connect scan tool MB991958. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 2.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

STEP 2. Using scan tool MB991958, read the occupant classification-ECU diagnostic trouble code.

Check if the DTC is set to the occupant classification-ECU.

Q. Is the DTC set?

YES Diagnose the occupant classification-ECU. Then go to Step 4.
NO Go to Step 3.
STEP 3. Using scan tool MB991958, read diagnostic trouble code No.
U0154 for other system.

Check if the DTC U0154 is set in ETACS-ECU, combination meter, A/C-ECU, KOS-ECU or WCM, hands free module, CAN box unit, radio and CD player, satellite radio tuner.

Q. Is the DTC set?

YES Replace the passenger seat cushion frame assembly Front Seat Assembly Removal and Installation).
NO Go to Step 4.
STEP 4. Recheck for diagnostic trouble code.

Check again if the DTC is set to the SRS-ECU.

(1)Erase the DTC.

(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.

(3)Check if DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Replace the SRS-ECU (Refer to Service and Repair).
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).