Code No.B1604: Seat belt pre-tensioner (driver’s side) (squib) system (open-circuited in the squib circuit)












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. 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)Disconnect seat belt pre-tensioner (driver’s side) connector C-18 <LHD> or C-31 <RHD>. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then 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 the diagnosis code No. B1604 set?

Go to Step 2

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

STEP 2. Resistance measurement at the B-111 SRS-ECU connector and the C-18 <LHD> or C-31 <RHD> seat belt pre-tensioner 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 prevents the seat belt pre-tensioner from operating unintentionally, disconnect the seat belt pre-tensioner (driver’s side) connector to short the squib circuit.
Disconnect seat belt pre-tensioner (driver’s side) connector C-18 <LHD> or C-31 <RHD>. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then 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 the short spring, and release the short spring.

(5)Connect special tool resistor harness (MB991884) to the removed C-18 <LHD> or C-31 <RHD> harness side connector.

(6)
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 resistor harness and B-111 harness side connector.

  • Continuity between B-111 SRS-ECU connector terminal No. 51 and resistor harness connector terminal No. 1
  • Continuity between B-111 SRS-ECU connector terminal No. 52 and resistor harness connector terminal No. 2
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?

Go to Step 3

Repair the harness wires between SRS-ECU connector B-111 (terminal No.51 and 52) and the seat belt pre-tensioner (driver’s side) connector C-18 <LHD> or C-31 <RHD> (terminal No.2 and 1)

STEP 3. Check whether the diagnosis code is reset.

Q. Is diagnosis code No.B1604 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).