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DTC B1603: Seat belt pre-tensioner (driver’s side) (squib) system (short circuit between squib circuit terminals)
 
 
cautionIf DTC B1603 is stored in the SRS-ECU, always diagnose the CAN main bus line.
 
 
CIRCUIT OPERATION
The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the analog G-sensor in the SRS-ECU. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, the pre-tensioner will deploy.
 
 
DTC SET CONDITIONS
This DTC is stored if there is abnormal resistance between the input terminals of the driver's side seat belt pre-tensioner (squib).
 
 
TROUBLESHOOTING HITS
  • Improper engaged connector or defective short spring*
  • Short circuit between the driver's seat belt pre-tensioner (squib) circuit terminals
  • Damaged connector(s)
  • Malfunction of the SRS-ECU
note*: The squib circuit connectors integrate a "short" spring (which prevents the seat belt pre-tensioner from deploying unintentionally due to static electricity by shorting the positive wire to the ground wire in the squib circuit when the connectors are disconnected) (Refer to ). Therefore, if connector is damaged or improperly engaged, the short spring may not be released when the connector is connected.
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). 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. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTC stored?
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. Connector check: SRS-ECU connector, seat belt pre-tensioner (driver’s side) connector.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever. After disconnecting the SRS-ECU connector, connect it again.
(3) After disconnecting the SRS-ECU harness side connector, connect the connector again. For the seat belt pre-tensioner (driver’s side) harness side connector disconnection, use the flat-tipped screwdriver to pull out the harness side connector locking button. After releasing the lock, disconnect the harness side connector.
(4) Connect the negative battery terminal.
(5) After erasing the DTC memory, check the DTC again.
(6) Disconnect the negative battery terminal.
Is DTC B1603 stored?
Go to Step 4.
Replace the connector concerned.
 
STEP 4. 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 seat belt pre-tensioner (driver’s side) harness side connector.
(3) Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4) Connect special tool resistor harness to the seat belt pre-tensioner (driver’s side) 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 B1603 stored?
Go to Step 5.
Replace the seat belt with pre-tensioner (driver’s side) (Refer to ).
 
STEP 5. Resistance check at the SRS-ECU connector (PTD+, PTD- line).
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the SRS-ECU connector.
(3)
dangerTo release the SRS-ECU connector short spring in the following operations, disconnect this seat belt pre-tensioner 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 seat belt pre-tensioner (RH) 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 [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] such as cable tie PTD+, PTD- line between the SRS-ECU connector and the seat belt pre-tensioner (RH) connector.
(5) Take the measurements below at the SRS-ECU harness side connector.
  • Continuity PTD+, PTD- line between the SRS-ECU connector and the seat belt pre-tensioner (RH) connector.
OK: No continuity
Is the check result normal?
Go to Step 6.
Repair the wiring harness PTD+, PTD- line between the SRS-ECU connector and the seat belt pre-tensioner (RH) connector.
 
STEP 6. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC B1603 stored?
Replace SRS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).