DTC 22

Driver's Air Bag Module (Squib) System Fault 2 (Open in the Squib Circuit)

Driver's Air Bag Module (Squib) Circuit:

CIRCUIT OPERATION
- The SRS-ECU judges how severe a collision is by detecting signals from the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU outputs an ignition signal. At this time, if the front air bag safing G-sensor is on, the SRS air bag will inflate.
- The ignition signal is input to the air bag module via the clock spring to inflate the air bag.

DTC SET CONDITIONS
- This DTC is set if an open circuit is detected between the terminals of the driver's side air bag module (squib). However, if the vehicle condition returns to normal, the SRS warning light will go out, but the DTC will be retained.

TROUBLESHOOTING HINTS
- Open circuit in the clock spring
- Open circuit due to improper neutral position of the clock spring
- Open circuit in the driver's air bag module (squib) circuit
- Disengaged driver's air bag module (squib) connector
- Improper connector contact
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991613: SRS Check Harness
- MB991865: Dummy Resistor
- MB991866: Resistor Harness
- MB991223 (MB991222): Harness Set (Probe)

STEP 1. Check the SRS-ECU to clock spring line.




1. Disconnect the clock spring connector C-204 (4-pin).




2. Connect special tool MB991865 to special tool MB991866.

CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.

3. Insert special tool MB991866 into the clock spring harness side connector C-204 (terminal No.3 and 4) by backprobing.
4. Connect the negative battery terminal.
5. Erase the DTC memory, and then recheck the DTC.

Q: Is DTC 22 set?

YES: Go to Step 3.
NO: Go to Step 2.

STEP 2. Check the clock spring and the driver's air bag module.
1. Disconnect the negative battery terminal.




2. Connect connector(4) of special tool MB991613 to clock spring connector C-208.
3. Connect connector (1) of special tool MB991613 to connector (2).
4. Connect terminals 22 to 24, and terminals 23 to 25 of special tool MB991613 to connector (5).
5. Connect the clock spring to the instrument panel wiring harness.
6. Connect the negative battery terminal.
7. Erase the DTC memory, and then recheck the DTC.

Q: Is DTC 22 set?

YES: Replace the clock spring. Then go to Step 4.
NO: Replace the driver's air bag module. Then go to Step 4.

STEP 3. Check the harness between the SRS-ECU connect or C-137 (terminal No.7 and 8) and the clock spring connector C-204 (terminal No.3 and 4) for open circuit.







1. Disconnect the SRS-ECU connector C-137 and the clock spring connector C-204.

CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.




2. Check for continuity between the following ?terminals.
C-137 connector C-204 connector

7 - 3

8 - 4

It should be less than 2 ohms.

Q: Does continuity exist?

YES: Erase the DTC memory, and recheck if any DTC sets. If DTC 22 sets, replace the SRS-ECU Then go to Step 4.
NO: Repair the harness wires between the SRS-ECU connector C-137 and the clock spring connector C-204. Then go to Step 4.

STEP 4. Check the DTC.

Q: Is DTC 22 set?

YES: Return to Step 1.
NO: The procedure is complete. (If no malfunctions are not found in all steps, an intermittent malfunction is suspected. Refer to INTRODUCTION, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.)