Code No.B1470: Seat Belt Pre-Tensioner (LH) (Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)




caution If diagnosis code B1470 is set in the SRS-ECU, always diagnose the CAN main bus line.

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 there is abnormal resistance between the input terminals of the seat belt pre-tensioner (LH) (squib).

PROBABLE CAUSES



note *: The squib circuit connectors integrate a "short" spring (which prevents the seat belt pre-tensioner from deploying unintentionally due to static electricity by shorting the positive wire to the earth wire in the squib circuit when the connectors are disconnected) (Refer to ). Therefore, if connector C-120 or D-19 is damaged or improperly engaged, the short spring may not be released when the connector is connected.

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the 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 54F, Diagnosis ).

STEP 2. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition: LOCK (OFF) position to ON
(3)On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code set?
Go to Step 3 .
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 3. M.U.T.-III diagnosis code
caution To prevent damage to M.U.T.-III MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting M.U.T.-III MB991958.
(1)Turn the ignition switch to the "ON" position.
(2)Check if the diagnosis code is set.
(3)Turn the ignition switch to the "LOOK (OFF)" position.

Q. Is diagnosis code B1519 set?
Go to Step 4 .
Go to Step 5 .

STEP 4. Connector lock check: SRS-ECU connector C-120 (M.U.T.-III diagnosis code).
(1)Disconnect the negative battery terminal.

(2)Disconnect the connectors C-120 and then reconnect them.
(3)Connect the negative battery terminal.
(4)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1470 set?

Go to Step 5 .

The procedure is complete. It is assumed that diagnosis code B1470 set as connector C-120, D-19 was engaged improperly.

STEP 5. Connector lock check: SRS-ECU connector C-120 and seat belt pre-tensioner (LH) connector D-19 (M.U.T.-III diagnosis code).
(1)Disconnect the negative battery terminal.



(2)Disconnect connectors C-120 and D-19, and then reconnect them. For connector D-19, use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.
(3)Connect the negative battery terminal.
(4)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1470 set?

Go to Step 6 .

The procedure is complete. It is assumed that diagnosis code B1470 set because connector C-120 or D-19 was engaged improperly.

STEP 6. Check the driver’s seat belt pre-tensioner (M.U.T.-III diagnosis code).
(1)Disconnect the negative battery terminal.


(2)Disconnect seat belt pre-tensioner (LH) connector D-19. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, 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-19 harness side connector.
(5)Connect the negative battery terminal.
(6)Erase diagnosis code memory, and then check the diagnosis code.

Q. Is diagnosis code B1470 set?

Go to Step 7 .

Replace the seat belt pre-tensioner (LH) (Refer to ).

STEP 7. Check the seat belt pre-tensioner (LH) circuit. Resistance measurement at the SRS-ECU connector C-120.

(1)Disconnect SRS-ECU connector C-120.


(2)
danger To prevent the seat belt pre-tensioner from deploying unintentionally, disconnect the seat belt pre-tensioner (LH) connector D-19 to short the squib circuit.
Disconnect seat belt pre-tensioner (LH) connector D-19. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.

(3)
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 7, 8 and the short spring to release the short spring.

(4)
caution Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
Check for continuity between C-120 harness side connector terminals 7 and 8.
OK: Open circuit.

Q. Is the check result normal?

Go to Step 8 .

Repair the harness wires between SRS-ECU connector C-120 (terminal No.7 and 8) and seat belt pre-tensioner (LH) connector D-19 (terminal No.1 and 2).

STEP 8. Check whether the diagnosis code is reset.

Q. Is diagnosis code B1470 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points ).