Code No.B1603: Seat belt pre-tensioner (driver’s side) (squib) system (short-circuit between terminals of the squib circuit)

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 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 short circuit occurs between the terminals of SRS-ECU seat belt pre-tensioner (driver’s side) (squib) circuit.

PROBABLE CAUSES

Damaged short spring ^*
Short circuit between terminals of seat belt pre-tensioner (driver’s side) (squib) circuit
Damaged connector(s)
Malfunction of SRS-ECU

note

*: The squib circuit connectors integrate a short spring (which prevents the seat belt pre-tensioner from being unintentionally deployed because of static electricity by shorting the positive wire to the earth wire in the squib circuit when the connectors are disconnected). Therefore, when the above codes are set, the short spring may not be released due to the damaged connector even when the connectors are connected.

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code.

Q. Is diagnosis code B1519 set?

	Go to Step 2

	Go to Step 3

STEP 2. Connector lock check: B-111 SRS-ECU connector.

(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.

(2)Disconnect the connectors B-111 and then reconnect it.

(3)Connect the negative auxiliary battery terminal.

(4)After erasing the diagnosis code memory, check the diagnosis code again.

(5)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1603 set?

	Go to Step 3

	The procedure is complete. It is assumed that diagnosis code B1603 set as connector B-111 was engaged improperly.

STEP 3. Connector lock check: B-111 SRS-ECU connector and C-18 <LHD> or C-31 <RHD> seat belt pre-tensioner connector (driver’s side).

(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.

(2)After disconnecting B-111 SRS-ECU and driver’s pre-tensioner connector (harness side), reconnect the connector. For the connector disconnection, use a flat-tipped screwdriver to pull out the harness side connector locking button. After releasing the lock, disconnect the connector.
(3)Connect the negative auxiliary battery terminal.
(4)After erasing the diagnosis code memory, check the diagnosis code again.
(5)Disconnect the negative auxiliary battery terminal.

Q. Is the diagnosis code No. B1603 set?

Go to Step 4

The procedure is complete. It is assumed that diagnosis code B1603 set as connector B-111 or C-18 <LHD> or C-31 <RHD> was engaged improperly.

STEP 4. Diagnosis check by dummy resistor connection.

(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.

(2)After disconnecting B-111 SRS-ECU and driver’s pre-tensioner connector (harness side), reconnect the connector. For C-18 <LHD> or C-31 <RHD> connector disconnection, use a flat-tipped screwdriver to pull out the harness side connector locking button. After releasing the lock, disconnect the connector.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4)Connect special tool (MB991884) to the C-18 <LHD> or C-31 <RHD> harness side connector.
(5)Connect the negative auxiliary battery terminal.
(6)After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1603 set?

Go to Step 5

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

STEP 5. Resistance measurement at the B-111 SRS-ECU connector.

(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.

(2)Disconnect the B-111 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 a flat-tipped screwdriver to pull out the locking button at the driver’s pre-tensioner connector (wiring harness side), then unlock and disconnect the 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 51/52 and the short spring, and release the short spring.
(5)

caution

Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.

Take the measurements below at the B-111 harness side connector.

Continuity between terminals 51 and 52

OK: No continuity

Q. Is the check result normal?

Go to Step 6.

Repair the wiring harness between the B-111 SRS-ECU connector terminal No. 51/52 and the C-18 <LHD> or C-31 <RHD> seat belt pre-tensioner connector terminal No. 2/1.

STEP 6. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1603 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 ).