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




OPERATION


The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analogue 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.

DIAGNOSIS CODE SET CONDITIONS


This diagnosis code is set if seat belt pre-tensioner (driver’s side) squib wire(s) are open-circuited.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. Check the diagnosis code by connecting a dummy resistor. (M.U.T.-III diagnosis code)
(1)Disconnect the negative battery terminal.


(2)Disconnect seat belt pre-tensioner (driver’s side) connector D-15 <LHD> or D-23 <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 D-15 <LHD> or D-23 <RHD> harness side connector.
(5)Connect the negative battery terminal.
(6)Erase diagnosis code memory, and then check the diagnosis code.

Q. Is diagnosis code B1604 set?

Go to Step 2.

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

STEP 2. Resistance measurement between SRS-ECU connector C-130(terminal No.29 and 30) and the seat belt pre-tensioner (driver’s side) connector D-15 <LHD>/D-23 <RHD> (terminal No.2 and 1).
(1)Disconnect the negative battery terminal.



(2)Disconnect SRS-ECU connector C-130 and seat belt pre-tensioner (driver’s side) connector D-15 <LHD> or D-23 <RHD>, and measure at the wiring harness side. For connector D-15 <LHD> or D-23 <RHD>, use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.

(3)Connect D-15 <LHD> or D-23 <RHD> harness side connector to special tool resistor harness (MB991884).

(4)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Resistance measurement between the following terminals.

  • SRS-ECU connector C-130 terminal No.29 and special tool terminal No.1
  • SRS-ECU connector C-130 terminal No.30 and special tool terminal No.2
OK: Continuity (Less than 2 Ω)

Q. Are the check results normal?

Go to Step 3.

Repair the harness wires between SRS-ECU connector C-130 (terminal No.29 and 30) and the seat belt pre-tensioner (driver’s side) connector D-15 <LHD>/D-23 <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 ).