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DTC B1632 Knee air bag module (squib) system (open circuit of squib circuit terminals)
 
 
cautionIf DTC B1632 is set in SRS-ECU, be sure to diagnose the CAN bus line.
 
 
OPERATION
Only when the frontal impact exceeding the threshold is simultaneously detected (turned ON) by the front impact sensor as well as by the analog G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the knee air bag module (squib).
 
 
TROUBLE JUDGMENT
The code is set when the open circuit occurs to the SRS-ECU driver's knee air bag module (squib) circuit.
 
 
PROBABLE CAUSES
  • Poor contact of connector
  • Open circuit to driver's knee air bag module (squib) circuit
  • Malfunction of 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 the ignition switch to the "LOCK" (OFF) position 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 the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
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. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
(1) Connect the negative battery terminal.
(2) After erasing the DTC memory, check the DTC again.
(3) Disconnect the negative battery terminal.
Is DTC B1632 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. Diagnosis check by dummy resistor connection.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the knee air bag module harness side connector.
(3) Connect the special tool dummy resistor (MB991865) to the special tool resistor harness (MB991884).
(4) Connect the special tool resistor harness to the knee air bag module harness side connector.
(5) Connect the negative battery terminal.
(6) After erasing the DTC memory, check the DTC again.
(7) Disconnect the negative battery terminal.
Is DTC B1632 set?
Go to Step 4.
Replace the knee air bag module (Refer to ).
 
STEP 4. Resistance measurement at the SRS-ECU connector and the knee air bag module connector.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Disconnect the SRS-ECU connector.
(3)
dangerTo release the SRS-ECU connector short spring in the following operations, disconnect this harness side connector, and keep the squib circuit shorted.
Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the knee air bag module harness side connector.
(4)
cautionThe short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm (0.16 inch) or more.
Insert an insulator [width: 3 mm (0.12 inch), thickness: 0.5 mm (0.02 inch)] such as cable tie between the KDS-, KDS+ line and the short spring, and release the short spring.
(5) Connect special tool resistor (MB991884) to the removed knee air bag module harness side connector.
(6) Take the measurements below at the resistor harness and C-126 harness side connector.
  • Continuity KDS- line between SRS-ECU connector and resistor harness connector
  • Continuity KDS+ line between SRS-ECU connector and resistor harness connector
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 5.
Repair the wiring harness KDS-, KDS+ line between the SRS-ECU connector and the knee air bag module connector.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC B1632 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 ).