CODE NO. U0173 Left side impact sensor (rear) communication error













caution If the diagnosis code U0173 is set to SRS-ECU, be sure to diagnose the CAN bus line.

OPERATION


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

TROUBLE JUDGMENT


The code is set if the communication with the left side impact sensor (rear) and side impact sensor (front), or with SRS-ECU is abnormal.

PROBABLE CAUSES



  • Malfunction of CAN bus line
  • Malfunction of left side impact sensor (rear)
  • Damaged wiring harness and connectors
  • Malfunction of SRS-ECU

DIAGNOSIS PROCEDURE


STEP 1. M.U.T.-III CAN bus diagnostics.


Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).

STEP 2. Check whether the diagnosis code is reset.


(1)Connect the negative battery terminal.
(2)After erasing the diagnosis code memory, check the diagnosis code again.
(3)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. U0173 set?

Go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

STEP 3. Left side impact sensor (rear) check.


(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2)Alternate the right side impact sensor (rear) and left side impact sensor (rear), and then install the alternated sensors.
(3)Connect the negative battery terminal.
(4)After erasing the diagnosis code memory, check the diagnosis code again.
(5)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. U0176 set?

Replace the left side impact sensor (rear) (Refer to ).
Go to Step 4.

STEP 4. Wiring harness check between the D-115 left side impact sensor (rear) connector terminal No. 1/2 and the D-121 left side impact sensor (front) terminal No. 4/3.



  • Open circuit check for power supply wires of side impact sensor front and rear

Q. Is the check result normal?

Go to Step 5.
Repair the wiring harness.

STEP 5. Wiring harness check between the D-121 left side impact sensor connector terminal No. 1/2 and the C-31 SRS-ECU connector terminal No. 49/50.



  • Open circuit check for the SRS-ECU power supply wire

Q. Is the check result normal?

Go to Step 6.
Repair the wiring harness.

STEP 6. Check whether the diagnosis code is reset.


Q. Is the diagnosis code No. U0173 set?

Replace SRS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).