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DTC B1605: Driver's Seat belt Pre-tensioner (Squib) System (Shorted to Squib Circuit Ground)
 
 

cautionIf DTC B1605 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 front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the front air bag safing G-sensor is on, 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 seat belt pre-tensioner (squib).
 
 
TROUBLESHOOTING HITS
  • Damaged wiring harnesses or connectors
  • Short to the ground in the driver's seat belt pre-tensioner (squib) harness
  • Malfunction of the SRS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
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.
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 the "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. Check the driver's seat belt pre-tensioner.
(1) Disconnect the negative battery terminal.
(2) Disconnect driver's seat belt pre-tensioner connector D-28. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.
(3) Connect special tool MB991865 to special tool MB991884.
(4) Connect special tool MB991884 to the D-28 harness side connector.
(5) Connect the negative battery terminal.
(6) Erase diagnostic trouble code memory, and check the diagnostic trouble code.
Is DTC B1605 stored?
Go to Step 4.
Replace the driver's seat belt with pre-tensioner (Refer to ). Then go to Step 6.
 
STEP 4. Check the driver's seat belt pre-tensioner circuit. Measure the resistance at the SRS-ECU connector C-124.
(1) Disconnect the negative battery terminal.
(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 C-124 SRS-ECU connector.

(3)
dangerTo prevent the seat belt pre-tensioner from deploying unintentionally, disconnect the driver’s seat belt pre-tensioner connector D-28 to short the squib circuit.
Disconnect driver's seat belt pre-tensioner connector D-28. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.

(4)
cautionInsert an insulator such as a cable tie to a depth of 4mm (0.16 inch) or more, otherwise the short spring will not be released.
Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 54, 55 and the short spring to release the short spring.

(5) Check for continuity between C-124 harness side connector terminals 54, 55 and body ground.It should be an open circuit.
Is it open circuit?
Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1605 is stored, replace the SRS-ECU (Refer to ). Then go to Step 6.
Go to Step 5.
 
STEP 5. Check harness wires for short circuit to ground between SRS-ECU connector C-124 (terminal No.54 and 55) and driver's seat belt pre-tensioner connector D-28 (terminal No.1 and 2).
Is the check result normal?
Go to Step 6.
Repair the harness wires between SRS-ECU connector C-124 and driver's seat belt pre-tensioner connector D-28. Then go to Step 6.
 
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 B1605 stored?
Return to Step 1.
The procedure is complete.