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Home >> Mitsubishi >> 2002 >> Lancer O-Z Rally Edition L4-2.0L SOHC >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> Manufacturer Code Charts >> Air Bag Systems >> DTC 21

DTC 21

Driver's Air Bag Module (Squib) System Fault 1 (Short Circuit between Terminal of 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
These DTC are output 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 below. However, if no DTC resets, the SRS warning light will be switched off (DTC will be retained).

TROUBLESHOOTING HINTS
- Improper engaged connector or defective short bar*
- Short circuit in the clock spring
- Short circuit between the driver's air bag module (squib) circuit terminals
- Damaged connector(s)
- Malfunction of the SRS-ECU

NOTE: *: The squib circuit connectors integrate a "short" bar (which prevents the air bag from deploying unintentionally due to static electricity by shorting the positive wire to the ground wire in the squib circuit when the connectors are disconnected). Therefore, if connector C-12 C-205 or C-201 is damaged or improperly engaged, the short bar may not be released when the connector is connected.

DIAGNOSIS

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

STEP 1. Check the DTC.

Q: Is DTC 34 output?

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




STEP 2. Check SRS-ECU connector C-12.

Q: Is the connector correctly engaged?

YES: Go to Step 3.
NO: Engage the connector correctly. Then go to Step 8.







STEP 3. Check SRS-ECU connector C-12, clock spring connector C-205 and driver's air bag module connector C-201.
1. Disconnect connectors C-12, C-205 and C-201, and then reconnect them.
2. Connect the negative battery terminal.
3. Erase the DTC memory, and then check the DTC.

Q: Is DTC 21 output?

YES: Go to Step 4.
NO: The inspection is complete. It is assumed that DTC 21 set as connector C-12, C-205 or C-201 was engaged improperly.







STEP 4. Check the driver's air bag module.
1. By sliding the A section (in the figure) of air bag module connector C-201 in the arrow direction, disconnect the connector
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 clock spring side air bag module connector C-201 by backprobing.
4. Connect the negative battery terminal.
5. Erase the DTC memory, and then recheck the DTC.

Q: Is DTC 21 output?

YES: Go to Step 5.
NO: Replace the driver's air bag module. Then go to Step B.




STEP 5. Check the clock spring.
1. Disconnect two-pin clock spring connector C-205.
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 clock spring harness side connector C-205 by backprobing.
4. Connect the negative battery terminal.
5. Erase the DTC memory, and then recheck the DTC.

Q: Is DTC 21 output?

YES: Go to Step 6.
NO: Replace the clock spring. Then go to Step 8.

STEP 6. Check harness between the SRS-ECU and the clock spring for short circuit.




1. Disconnect SRS-ECU connector C-12.






CAUTION: To release the short bar in the SRS-ECU connector, disconnect connector C-205 to short the squib circuit.

2. Disconnect the clock spring connector C-205.






CAUTION: Insert an insulator such as a cable tie to a depth of 4 mm (0.16 inch) or more, otherwise the short bar will not be released.

3. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 11,12 and the short bar to release the short bar.
4. 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.




5. Check the continuity between terminals 11 and 12.
- There should be open circuit.

Q: Is the continuity normal?

YES: Erase the DTC memory, and recheck if any DTC sets. If DTC 21 sets, replace the SRS-ECU. Then go to Step 8.
NO: Go to Step 7.







STEP 7. Check the harness for short circuit between SRS-ECU connector C-12 and clock spring connector C-205.

Q: Are harness wires between SRS-ECU connector C-12 and clock spring connector C-205 in good condition?

YES: Go to Step 8.
NO: Repair the harness wires between SRS-ECU connector C-12 and clock spring connector C-205 Then go to Step 8.

STEP 8. Check the DTC.

Q: Is DTC 21 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.)
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