B1490

DTC B1490: Passenger's (Front) Air Bag Module (2nd Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit)

Passenger's (Front) Air Bag Module (1st Squib And 2nd Squib) Circuit Part 1:

Passenger's (Front) Air Bag Module (1st Squib And 2nd Squib) Circuit Part 2:

CAUTION: If DTC B1410 <1st squib> or B1490 <2nd squib> is set in the SRS-ECU, always diagnose the CAN main bus line.

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 sends 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 passenger's side air bag module (squib). However, if no DTC reset, the SRS warning light will be switched off (DTC will be retained).

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

NOTE: *: The squib circuit connectors integrate a "short" spring (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). (Refer to Description and Operation/General Description). Therefore, if connector C-121 or C-110 is damaged or improperly engaged, the short spring may not be released when the connector is connected.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991910: MUT-III Main Harness A (Vehicles with CAN Communication System)
- MB991865: Dummy resister
- MB991866: Resister harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.




1. Connect scan tool MB991958. Refer to "How to connect the scan tool." Reading Diagnostic Trouble Codes
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES: Go to Step 2.

NO: Repair the CAN bus line (Refer to Diagnosis). Component Tests and General Diagnostics




STEP 2. 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 the DTC set?

YES: Go to Step 3.

NO: There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to How to Cope with Intermittent Malfunction).




STEP 3. Using scan tool MB991958, read the diagnostic trouble code.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1. Turn the ignition switch to the "ON" position.
2. Check if the DTC is set.
3. Turn the ignition switch to the "LOOK (OFF)" position.

Q: Is DTC B1519 set?

YES: Go to Step 4.

NO: Go to Step 5.




STEP 4. Check SRS-ECU connector C-121.

Q: Is the connector correctly engaged?

YES: Go to Step 5.

NO: Engage the connector correctly. Then go to Step 9.

STEP 5. Check SRS-ECU connector C-121 and passenger's air bag module connector C-110. (Using scan tool MB991958, read the diagnostic trouble code.)

1. Disconnect the negative battery terminal.







2. Disconnect connectors C-121 and C-110, and then reconnect them.




3. Slide the outer housing of the clock spring side of driver's air bag module connector C-110 in the arrow direction shown, and disconnect the connector.
4. Connect the negative battery terminal.
5. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC B1410 <1st squib> or B1490 <2nd squib> set?

YES: Go to Step 6.

NO: The procedure is complete. It is assumed that DTC B1410 <1st squib> or B1490 <2nd squib> set as connector C-121 or C-110 was engaged improperly.

STEP 6. Check the passenger's air bag module. (Using scan tool MB991958, read the diagnostic trouble code.)

1. Disconnect the negative battery terminal.




2. Disconnect the passenger's air bag module connector C-110.




3. Slide the outer housing of the clock spring side of passenger's air bag module connector C-110 in the arrow direction shown, and disconnect the connector.




4. 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.

5. Insert special tool MB991866 into the harness side connector C-110 (terminal No.1 and 2 <1st squib> or terminal No.3 and 4 <2nd squib>) by backprobing.
6. Connect the negative battery terminal.
7. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC B1410 <1st squib> or B1490 <2nd squib> set?

YES: Go to Step 7.

NO: Replace the passenger's air bag module. Then go to Step 9.

STEP 7. Check the passenger's air bag module circuit at SRS-ECU connector C-121.




1. Disconnect SRS-ECU connector C-121.






DANGER: To prevent the air bag from deploying unintentionally, disconnect the passenger's air bag module connector C-110 to short the squib circuit.

2. Disconnect the passenger's air bag module connector C-110.




3. Slide the outer housing of the clock spring side of driver's air bag module connector C-110 in the arrow direction shown, and disconnect the connector.









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

4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 27 and 28 <1st squib> or 30 and 31 <2nd squib>, and the short spring to release the short springr.









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 for continuity between C-121 harness side connector terminals 27 and 28 <1st squib> or 30 and 31 <2nd squib>.
It should be open circuit.

Q: Does continuity exist?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1410 <1st squib> or B1490 <2nd squib> set, replace the SRS-ECU. Then go to Step 9.

NO: Go to Step 8.










STEP 8. Check the harness for short circuit between SRS-ECU connector C-121 (terminal No.27 and 28 <1st squib> or terminal No.30 and 31 <2nd squib>) and passenger's air bag module connector C-110 (terminal No.1 and 2 <1st squib> terminal No.4 and 3 <2nd squib>).

NOTE: After inspecting intermediate connector C-22 inspect the wiring harness. If the intermediate connector C-22 is damaged, repair or replace it.

Q: Are harness wires between SRS-ECU connector C-121 (terminal No.27 and 28 <1st squib> or terminal No.30 and 31 <2nd squib>) and passenger's air bag module connector C-110 (terminal No.1 and 2 <1st squib> terminal No.4 and 3 <2nd squib>) in good condition?

YES: Go to Step 9.

NO: Replace the harness wires between SRS-ECU connector C-121 and passenger's air bag module connector C-110. Then go to Step 9.




STEP 9. Check 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 B1410 <1st squib> or B1490 <2nd squib> set?

YES: Return to Step 1.

NO: The procedure is complete.