Diagnosis code 22: Driver's Air Bag Module (Squib) System Fault 2 (Open in the Squib Circuit)

OPERATION

The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and 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.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code 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 the followings:

Open circuit in the driver's air bag module (squib) or harness

Open circuit in the clock spring

Malfunction of connector contact

However, if no diagnosis code resets, the SRS warning lamp will be switched off (diagnosis code will be retained).

PROBABLE CAUSES

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 PROCEDURE

STEP 1. Check the driver's air bag module (Check whether the diagnosis code is reset).

Disconnect the negative battery terminal.

By sliding the A section (in the figure) of air bag module connector C-306 in the arrow direction, disconnect the connector.

Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).

CAUTION

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

Insert special tool MB991866 into clock spring side air bag module connector C-306 by backprobing.

Connect the negative battery terminal.

Erase the diagnosis code memory, and check the diagnosis code.

Q: Is diagnosis code 22 set?

YES: Go to Step 2

.
NO: Replace the driver's air bag module (Refer to

). Then go to Step 4

STEP 2. Check the clock spring (Check whether the diagnosis code is reset).

Disconnect the negative battery terminal.

Disconnect the clock spring connector C-307.

Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).

CAUTION

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

Insert special tool MB991866 into clock spring harness side connector C-307 (terminal No.3 and 4) by backprobing.

Connect the negative battery terminal.

Erase the diagnosis code memory, and check the diagnosis code.

Q: Is diagnosis code 22 set?

YES: Go to Step 3

.
NO: Replace the clock spring (Refer to

). Then go to Step 4

STEP 3. Check the harness between the SRS-ECU connector C-115 (terminal No.11 and 12) and the clock spring connector C-307 (terminal No.3 and 4) for open circuit.

Disconnect SRS-ECU connector C-115 and clock spring connector C-307.

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 the following terminals.

SRS-ECU connector C-115 (terminal No.11) and the clock spring connector C-307 (terminal No.3)

SRS-ECU connector C-115 (terminal No.12) and the clock spring connector C-307 (terminal No.4)

OK: Less than 2 Ω

Q: Are the check results normal?

YES: Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 22 sets, replace the SRS-ECU (Refer to

). Then go to Step 4

.
NO: Repair the harness wires between SRS-ECU connector C-115 and clock spring connector C-307. Then go to Step 4

STEP 4. Check whether the diagnosis code is reset.

Q: Is diagnosis code 22 set?

YES: Return to Step 1

.
NO: The procedure is complete (If no malfunctions are found in all steps, an intermittent malfunction is suspected). Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points


Diagnosis code 22: Driver's Air Bag Module (Squib) System Fault 2 (Open in the Squib Circuit)

OPERATION The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and 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.
DIAGNOSIS CODE SET CONDITIONS This diagnosis code 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 the followings: Open circuit in the driver's air bag module (squib) or harness Open circuit in the clock spring Malfunction of connector contact However, if no diagnosis code resets, the SRS warning lamp will be switched off (diagnosis code will be retained).
PROBABLE CAUSES 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 PROCEDURE

	STEP 1. Check the driver's air bag module (Check whether the diagnosis code is reset). Disconnect the negative battery terminal.
	By sliding the A section (in the figure) of air bag module connector C-306 in the arrow direction, disconnect the connector.
	Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866). CAUTION Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened. Insert special tool MB991866 into clock spring side air bag module connector C-306 by backprobing. Connect the negative battery terminal. Erase the diagnosis code memory, and check the diagnosis code. Q: Is diagnosis code 22 set? YES: Go to Step 2. NO: Replace the driver's air bag module (Refer to ). Then go to Step 4.
	STEP 2. Check the clock spring (Check whether the diagnosis code is reset). Disconnect the negative battery terminal. Disconnect the clock spring connector C-307.
	Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866). CAUTION Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened. Insert special tool MB991866 into clock spring harness side connector C-307 (terminal No.3 and 4) by backprobing. Connect the negative battery terminal. Erase the diagnosis code memory, and check the diagnosis code. Q: Is diagnosis code 22 set? YES: Go to Step 3. NO: Replace the clock spring (Refer to ). Then go to Step 4.
	STEP 3. Check the harness between the SRS-ECU connector C-115 (terminal No.11 and 12) and the clock spring connector C-307 (terminal No.3 and 4) for open circuit. Disconnect SRS-ECU connector C-115 and clock spring connector C-307.
	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 the following terminals. SRS-ECU connector C-115 (terminal No.11) and the clock spring connector C-307 (terminal No.3) SRS-ECU connector C-115 (terminal No.12) and the clock spring connector C-307 (terminal No.4) OK: Less than 2 Ω Q: Are the check results normal? YES: Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 22 sets, replace the SRS-ECU (Refer to ). Then go to Step 4 . NO: Repair the harness wires between SRS-ECU connector C-115 and clock spring connector C-307. Then go to Step 4.
	STEP 4. Check whether the diagnosis code is reset. Q: Is diagnosis code 22 set? YES: Return to Step 1 . NO: The procedure is complete (If no malfunctions are found in all steps, an intermittent malfunction is suspected). Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points .