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DTC U0172: Side Impact Sensor (LH) Communication Error








caution If DTC U0172 is set in the SRS-ECU, always diagnose the CAN main bus line.

CIRCUIT OPERATION


If an impact of set value or more is detected, the side impact sensor sends the coded acceleration data to SRS-ECU. Based on the acceleration data, SRS-ECU determines the necessity of side-airbag and curtain air bag deployment, and then turns ON the power supply circuit to the inflator.

DTC SET CONDITIONS


These DTCs are set if communication between the side impact sensor (LH) and the SRS-ECU is not possible or faulty.

TROUBLESHOOTING HINTS



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 (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 ."
(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?

Go to Step 2.

Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).

STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1)Erase the DTC.
(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 set?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 3. Check for any diagnostic trouble code.
Check the side impact sensor (LH).
(1)Disconnect the negative battery terminal.
(2)Alternate the side impact sensor (LH) and side impact sensor (RH), and then install the alternated sensors.
(3)Connect the negative battery terminal.
(4)Erase diagnostic trouble code from memory, and check the diagnostic trouble code.

Q. Is DTC U0175 set?
Replace the side impact sensor (LH) with a new one (Refer to ). Go to Step 5.
Go to Step 4.

STEP 4. Check the harness wires for open circuit and short circuit between SRS-ECU connector C-30 (terminal No.49 and 50) and side impact sensor (LH) connector D-22 (terminal No.1 and 2).

Q. Are the harness wires between SRS-ECU connector C-30 (terminal No.49 and 50) and side impact sensor (LH) connector D-22 (terminal No.1 and 2) in good condition?

Go to Step 5.
Repair the harness wires between SRS-ECU connector C-30 and side impact sensor (LH) connector D-22.

STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1)Erase the DTC.
(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 DTC U0172 set?
Replace the SRS-ECU (Refer to ).
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).