Code No.4A: Curtain air bag module (squib) (LH) system (short-circuited between terminals of the squib circuit)




OPERATION


The SRS-ECU judges how severe a collision is by detecting signals from the side impact sensors and the side air bag safing G-sensor. If the impact is over a predetermined level, the SRS-ECU outputs an ignition signal. At this time, if the side air bag safing G-sensor is on, the curtain air bag module will deploy.

DIAGNOSIS CODE SET CONDITIONS


This diagnosis code is set if one curtain air bag module squib (LH) wire shorted to the other. However, if no diagnosis code resets, the SRS warning lamp will be switched off (diagnosis code will be retained).

PROBABLE CAUSES



note *: The squib circuit connectors integrate a "short" spring (which prevents the air bag 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). Therefore, if connector C-146, G-01 or G-22 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 diagnosis code

Q. Is diagnosis code 34 set?
Go to Step 2.
Go to Step 3.

STEP 2. Connector lock check: SRS-ECU connector C-146 (M.U.T.-III diagnosis code).
(1)Disconnect the negative battery terminal.

(2)Disconnect connectors C-146, and then reconnect them.
(3)Connector the negative battery terminal.
(4)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code 4A set?

Go to Step 3.

The procedure is complete. It is assumed that diagnosis code 4A set as connector C-146 was engaged improperly.

STEP 3. Connector lock check: SRS-ECU connector C-146, intermediate connector G-22 and curtain air bag module connector G-01 (M.U.T.-III diagnosis code).


(1)Disconnect the negative battery terminal.




(2)Disconnect connectors C-146, G-22 and G-01, and then reconnect them. For connector G-01, use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.
(3)Connector the negative battery terminal.
(4)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code 4A set?

Go to Step 4.

The procedure is complete. It is assumed that diagnosis code 4A set as connector C-146, G-22 or G-01 was engaged improperly.

STEP 4. Check the diagnosis code by connecting a dummy resistor (M.U.T.-III diagnosis code).
(1)Disconnect the negative battery terminal.

(2) Disconnect intermediate connector G-22 (connection between curtain air bag harness and floor harness).

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Connect special tool (MB991884) to the G-22 harness side connector by back probing.
(5)Connect the negative battery terminal.
(6)Erase diagnosis code memory, and then check the diagnosis code.

Q. Is diagnosis code 4A set?

Go to Step 5.

Go to Step 6.

STEP 5. Resistance measurement at the SRS-ECU connector C-146.
(1)Disconnect the negative battery terminal.


(2)Disconnect SRS-ECU connector C-146.
danger To prevents the air bag from deploying unintentionally, disconnect the curtain air bag harness connector G-22 to short the squib circuit.

(3)
caution Insert an insulator such as a cable tie to a depth of 4mm or more, otherwise the short bar will not be released.
Insert a cable tie [3 mm wide, 0.5 mm thick] between terminals 27, 28 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.
Resistance measurement between C-146 harness side connector terminals 27 and 28.
OK: Open circuit

Q. Is the check result normal?

Go to Step 7.

Repair the harness wire between SRS-ECU connector C-146 (terminal No.27 and 28) and harness side connector G-22 (terminal No.1and 2).

STEP 6. Resistance measurement at intermediate connector G-22.

(1)Disconnect the negative battery terminal.
danger To prevents the air bag from deploying unintentionally, disconnect the curtain air bag module connector G-01 to short the squib circuit.

(2)Disconnect curtain air bag module connector G-01. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.
(3) Disconnect intermediate connector G-22 (connection between curtain air bag harness and floor harness).

(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 1, 2 and the short spring to 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.
Resistance measurement between G-22 curtain air bag module (LH) side connector terminals 1 and 2.
OK: Open circuit

Q. Is the check result normal?

Replace the curtain air bag module (Refer to).

Repair the harness wire between curtain air bag module (LH) side connector G-22 (terminal No.1 and 2) and curtain air bag module connector G-01 (terminal No.1and 2).

STEP 7. Check whether the diagnosis code is reset.


Q. Is diagnosis code 4A set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points ).