Code No.B1605 Seat belt pre-tensioner (driver’s side) (squib) system (shorted to squib circuit earth)

caution

If the diagnosis code B1605 is set to 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 analogue G-sensor and safing G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the seat belt pre-tensioner (squib).

TROUBLE JUDGEMENT

The code is set when the input terminal of SRS-ECU seat belt pre-tensioner (driver’s side) (squib) is shorted to earth

PROBABLE CAUSES

Damaged wiring harness and connector
Seat belt pre-tensioner (driver’s side) (squib) harness shorted to earth.
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. B1605 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 D-28 <LHD> and D-03 <RHD> harness side connector.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4)Connect special tool resistor harness to the D-28 <LHD> and D-03 <RHD> 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. B1605 set?

Go to Step 4.

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

STEP 4. Resistance measurement at the C-124 SRS-ECU 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 C-124 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 D-28 <LHD> and D-03 <RHD> 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 terminal 54/55 the short spring, and release the short spring.
(5)Take the measurements below at the C-124 harness side connector.

Continuity between terminal No. 54/55 and body earth

OK: No continuity

Q. Is the check result normal?

Go to Step 5.

Repair the wiring harness between the C-124 SRS-ECU connector terminal No. 54/55 and the D-28 <LHD> and D-03 <RHD> seat belt pre-tensioner connector terminal No. 1/2.

STEP 5. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1605 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 ).