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 there is abnormal resistance between the input terminals of the driver's side air bag module (squib). The most likely causes for this code to be set are shown in the table: However, if no DTC resets, the SRS warning light will be switched off (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

Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991613: SRS Check Harness
- MB991865: Dummy resister
- MB991866 Resister harness

STEP 1. Check the driver's air bag module.

1. Disconnect the negative battery terminal.
2. Remove the driver's air bag module.




3. Connect connector (4) of special tool MB991613 to clock spring connector C-81. Special tool MB991613 to special tool MB991866.
4. Connect connector (1) of special tool MB991613 to connector (2).
5. Connect terminals 22 to 24, and terminals 23 to 25 of special tool MB991613 to connector (5).
6. Connect the clock spring to the body wiring harness.
7. Connect the negative battery terminal.
8. Erase the DTC memory, and then recheck the DTC.

Q: Is DTC 22 out put?

YES: Go to Step 2.

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

STEP 2. Check the clock spring.

1. Disconnect the negative battery terminal.
2. Disconnect the clock spring connector C-85.




3. 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.

4. Insert special tool MB991866 into clock spring harness side connector C-85 (terminal No.3 and 4) by backprobing.
5. Connect the negative battery terminal.
6. Erase the DTC memory, and then recheck DTC.

Q: Is DTC 22 output?

YES: Go to Step 3.

NO: Replace the clock spring. Then go to Step 4.

STEP 3. Check the harness between the SRS-ECU and the clock spring for open circuit.










1. Disconnect SRS-ECU connector C-72 and clock spring connector C-85, and measure at the wiring harness side.

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 the continuity between the following terminals.
C-72 connector C-85 connector
7 3
8 4
- Should be less than 2 Ohms.

Q: Is the continuity normal?

YES: Eras 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 SRS-ECU connector C-72 and clock spring connector C-85.
Then go to Step 4.

STEP 4. Check the DTC.

Q: Is DTC 22 output?

YES: Return to Step 1.

NO: This diagnosis is complete. (If no malfunctions are not found in all steps, an intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.)