Code No.B1604 Seat belt pre-tensioner (driver’s side) (squib) system (open circuit of squib circuit)


caution If the diagnosis code B1604 is set to SRS-ECU, be sure to diagnose the CAN bus line.

OPERATION



TROUBLE JUDGEMENT



PROBABLE CAUSES



  • Open circuit to seat belt pre-tensioner (driver’s side) (squib) circuit
  • Damaged wiring harness and connector
  • 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. B1604 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 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 the 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 diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1604 set?

Go to Step 4.

Replace the seat belt with pre-tensioner (driver’s side) (Refer to ).

STEP 4. Resistance measurement at the SRS-ECU connector and the 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, and disconnect the SRS-ECU connector.

(3)
danger To 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 (driver’s side) harness side connector.

(4)
caution The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm or more.
Insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the PTD-, PTD+ line the short spring, and release the short spring.

(5)Connect special tool resistor harness (MB991884) to the removed seat belt pre-tensioner (driver’s side) harness side connector.

(6)Take the measurements below at the resistor harness and SRS-ECU harness side connector.

  • Continuity PTD- line between SRS-ECU connector and resistor harness connector
  • Continuity PTD+ line between SRS-ECU connector and resistor harness connector
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?

Go to Step 5.

Repair the wiring harness PTD-, PTD+ line between the SRS-ECU connector and the seat belt pre-tensioner (driver’s side) connector.

STEP 5. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1604 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 ).