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DTC B1408: Front Impact Sensor (RH) Communication Error
DTC B1409: Front Impact Sensor (RH) Communication Impossible
 
 
cautionIf DTC B1408 or B1409 is set in the SRS-ECU, always diagnose the CAN main bus line.
 
 
CIRCUIT OPERATION
The front impact sensor (RH) transmits acceleration data to the SRS-ECU. The SRS-ECU then determines whether to operate the front air bags, and then outputs an ignition signal when necessary. The front impact sensor also diagnoses itself, and sends a DTC to the SRS-ECU if a malfunction occurs.
 
 
DTC SET CONDITIONS
The DTC is set if the communication between the front impact sensor (RH) and SRS-ECU is abnormal (No. B1408), or impossible (No. B1409).
 
 
TROUBLESHOOTING HINTS
  • Damaged wiring harnesses or connectors
  • Malfunction of the front impact sensor (RH)
  • Malfunction of the SRS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the scan tool ."
(2) Turn on the power supply mode of the electric motor switch.
(3) Diagnose the CAN bus line.
(4) Turn off the power supply mode of the electric motor switch.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ). Then go to Step 2.
 
STEP 2. Recheck for DTC.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn on the power supply mode of the electric motor switch.
(3) Check if the DTC is set.
(4) Turn off the power supply mode of the electric motor switch.
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 the front impact sensor (RH).
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Alternate the front impact sensor (RH) and the front impact sensor (LH), and then install the alternated sensor.
(3) Connect the negative battery terminal.
(4) After erasing the DTC memory, check the DTC again.
(5) Disconnect the negative battery terminal.
Is DTC B1408 or B1409 set?
Replace the front impact sensor (RH) with a new one. (Refer to ).
Go to Step 4.
 
STEP 4. Check of short to power supply, short to ground, and open circuit in FRH-, FRH+ line between SRS-ECU connector and front impact sensor (RH) connector.
Is the check result normal?
Go to Step 5.
Repair the wiring harness.
 
STEP 5. Recheck for DTC.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn on the power supply mode of the electric motor switch.
(3) Check if the DTC is set.
(4) Turn off the power supply mode of the electric motor switch.
Is DTC B1408 or B1409 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 ).