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




OPERATION



DIAGNOSIS CODE SET CONDITIONS



PROBABLE CAUSES



  • Improper connector contact
  • Open circuit in the seat belt pre-tensioner (driver’s side) (squib) circuit
  • Malfunction of the SRS-ECU

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-155 (terminal No.51 and 52) and the seat belt pre-tensioner (driver’s side) connector D-15 <LHD> or D-23 <RHD> (terminal No.2 and 1).
(1)Disconnect the negative battery terminal.

(2)Disconnect SRS-ECU connector C-155.


(3)
danger To prevents the seat belt pre-tensioner from operating unintentionally, disconnect the seat belt pre-tensioner (driver’s side) connector D-15 <LHD> or D-23 <RHD> to short the squib circuit.
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.

(4)
caution Insert an insulator such as a cable tie to a depth of 4mm or more, otherwise the short spring will not be released.
Insert a cable tie [3 mm wide, 0.5 mm thick] between terminals 51, 52 and the short spring to release the short spring.

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

(6)
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-155 terminal No.51 and special tool terminal No.1
  • SRS-ECU connector C-155 terminal No.52 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-155 (terminal No.51 and 52) and the seat belt pre-tensioner (driver’s side) connector D-15 <LHD> or 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 ).