DTC U0171: Front Impact Sensor (RH) Communication Error: 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)

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

   • YES:  Go to Step 2.
   • NO:  Repair the CAN bus line (Refer to DIAGNOSIS ).
     Fig 1: Connecting Special Tool MB991910 To Data Link Connector

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. 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? 

   • YES:  Go to Step 3.
   • NO:  There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
3. STEP 3. Check for any diagnostic trouble code. 

   Check the front impact sensor (RH).

   1. Disconnect the negative battery terminal.
   2. Alternate the front impact sensor (RH) and front impact sensor (LH), 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 U0170 set? 

   • YES:  Replace the front impact sensor (RH) with a new one (Refer to FRONT IMPACT SENSORS  ). Go to  Step 5.
   • NO:  Go to Step 4.
4. STEP 4. Check the harness wires for open circuit and short circuit between SRS-ECU connector C-122 (terminal No. 23 and 24) and front impact sensor (RH) connector A-41 (terminal No. 2 and 1). 
   NOTE: After inspecting intermediate connector A-33, C-128 inspect the wiring harness. If the intermediate connector A-33, C-128 is damaged, repair or replace it.

   Q: Are the harness wires between SRS-ECU connector C-122 (terminal No. 23 and 24) and front impact sensor (RH) connector A-41 (terminal No. 2 and 1) in good condition? 

   • YES:  Go to Step 5.
   • NO:  Repair the harness wires between SRS-ECU connector C-122 and front impact sensor (RH) connector A-41.
5. 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 U0171 set? 

   • YES:  Replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ).
   • NO:  There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).