B1401
This document has been updated per Mitsubishi TSB# 06-52b-001DTC B1401: Driver's Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit)
DTC B1481: Driver's Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit)
Driver's Air Bag Module (1st And 2nd Squib) Circuit:
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.
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 the following:
- Open circuit in the driver's air bag module (squib) or harness
- Open circuit in the clock spring
- Malfunction of connector contact
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:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: MUT-III USB Cable
- MB991910: MUT-III Main Harness A
- MB991865: Dummy resister
- MB991866: Resister harness
STEP 1. Check the driver's air bag module. (Using scan tool MB991958, read the diagnostic trouble code.)
1. Disconnect the negative battery terminal.
2. Slide the outer housing of the driver' s air bag module connector C-201 in the arrow direction shown, and disconnect the connector.
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 side of driver's air bag module connector C-201 (terminal No.1 and 2 <1st squib> or terminal No.3 and 4 <2nd squib>) by backprobing.
5. Connect the negative battery terminal.
CAUTION: Always DTC B1481 is set when checking DTC B1401. This is because the second side terminal is isolated when checking it, DTC B1481 is set but this is not a fault. In addition, always DTC B1401 is set when checking DTC B1481 because the first side terminal is isolated.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q: Is DTC B1401 <1st squib> or B1481 <2nd squib> set?
YES: Go to Step 2.
NO: Replace the driver's air bag module. Then go to Step 4.
STEP 2. Check the clock spring. (Using scan tool MB991958, read the diagnostic trouble code.)
1. Disconnect the negative battery terminal.
2. Disconnect the clock spring connector C-205.
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 harness side of clock spring connector C-205 (terminal No.3 and 4 <1st squib> or terminal No.1 and 2 <2nd squib>) by backprobing.
5. Connect the negative battery terminal.
CAUTION: Always DTC B1481 is set when checking DTC B1401. This is because the second side terminal is isolated when checking it, DTC B1481 is set but this is not a fault. In addition, always DTC B1401 is set when checking DTC B1481 because the first side terminal is isolated.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q: Is DTC B1401 <1st squib> or B1481 <2nd squib> set?
YES: Go to Step 3.
NO: Replace the clock spring. Then go to Step 4.
STEP 3. Check the harness between the SRS-ECU connector C-28 and the clock spring connector C-205 for open circuit.
1. Disconnect the negative battery terminal.
2. Disconnect SRS-ECU connector C-28 and clock spring connector C-205.
CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
3. Check for continuity between the following terminals. It should be less than 2 ohms.
<1st squib>
- SRS-ECU connector C-28 (terminal No.36) and the clock spring connector C-205 (terminal No.3)
- SRS-ECU connector C-28 (terminal No.37) and the clock spring connector C-205 (terminal No.4)
<2nd squib>
- SRS-ECU connector C-28 (terminal No.33) and the clock spring connector C-205 (terminal No.1)
- SRS-ECU connector C-28 (terminal No.34) and the clock spring connector C-205 (terminal No.2)
Q: Does continuity exist?
YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1401 <1st squib> or B1481 <2nd squib> set, replace the SRS-ECU. Then go to Step 4.
NO: Replace the harness wires between SRS-ECU connector C-28 and clock spring connector C-205. Then go to Step 4.
STEP 4. Recheck for diagnostic trouble code.
Check again if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC B1401 <1st squib> or B1481 <2nd squib> set?
YES: Return to Step 1.
NO: The procedure is complete.