Air Bag System - Diagnosis/Troubleshooting
Bulletin No.: 014/96Issued: 06/27/96
Revised: 08/10/96
Category
T
Applicable Model/s
See Below
Subject:
AIR BAG WARNING LIGHT
The revised section of this bulletin is indicated with an asterisk. Replace the original bulletin with this revised copy.
APPLICABLE MODELS
1995 and after Protege, Millenia and 626 / MX-6 (GE)
DESCRIPTION
This Service Bulletin contains prominent service points for air bag system troubleshooting.
This information will reduce the amount of unnecessary air bag replacements when the air bag system warning light illuminated.
CAUTION:
1. In some cases the air bag system warning light illuminates under the normal operating condition. If insufficient voltage is supplied to the SAS unit (for example the battery is dead), the warning light may come on.
2. If the air bag system warning light illuminates, pay close attention to the investigation of the main cause of this problem.
CONDITIONS LEADING TO AIR BAG LIGHT ILLUMINATION
1. A poor air bag module connector connection is a possible cause.
^ The air bag module and the horn are connected in series to the clock spring with a double-lock type connector. If the horn does not sound, the air bag module connectors may be the possible cause.
2. The voltage supplied to the SAS unit goes down momentarily, then recovers. Cause:
^ Battery Not Fully Charged
^ Battery Deteriorated
3. If a large load is applied to the battery momentarily under one of the above conditions (Battery Not Fully Charged, Battery Deteriorated), the voltage supplied to the SAS unit goes down, and the warning light illuminates. Even if the voltage goes up, the warning light stays on for a while.
4. There is a possibility of momentary poor connection in the system connectors.
^ The connectors may be connected incompletely, or a short-circuit may occur in the wire.
^ Even if the connection of the connectors is presently good, there is a possibility that the problem will recur in the future. To avoid this, it is necessary to inspect the connectors.
^ If you receive repeated customer complaints, a closer inspection is necessary.
5. Problem exists in the air bag warning circuit.
^ Repair the faulty circuit according to the Workshop Manual (Section T).
6. Problem exists in the air bag system.
^ Determine the malfunction location according to the diagnostic trouble code in the Workshop Manual (Section T, and then take a corrective action.
A. Air bag warning light flashes 3 times.
This condition is caused when an insufficient amount of voltage is available for the SAS unit (i.e. during long cranking and similar conditions).
^ As the voltage goes up, the warning light returns to normal. Even if the warning light illuminates. there as no problem with the system including the SAS unit.
^ Check the battery voltage, and charge the battery if necessary.
B. Air bag warning light stays on.
The major cause is an SAS unit internal problem or a not completely connected connector. Verify that the connector of SAS unit is properly connected.
1. Turn the ignition switch to ON, and confirm that the warning light stays on.
^ If the warning light does not stay on during inspection but the customer complains that the light has illuminated for a long time, proceed to step 2.
2. Push in the connector of the SAS unit, and confirm that a click is heard.
^ If a click is heard, a not completely connected connector is the cause of warning light staying on. The inspection is completed.
^ If a click is not heard, turn the ignition off and remove the connector to see if any foreign substances have entered. If found, remove and proceed to step 3.
CAUTION:
^ Don't pull connector out. Just push in the not completely connected connector.
^ Don't give a shock to the unit. Otherwise the air bag system is inflated.
3. Visually inspect the terminals of the connector.
^ Confirm that there is no crack in the connector.
^ Check that terminals 1 and 2 make contact with the appropriate areas of the unit.
4. Confirm that the resistance between terminals V and Y is 0 ohms.
^ If no problem is found, the connector is good.
NOTE:
If the resistance is not 0 ohms, inspect the harness between the terminals V and Y and repair the faulty location.
* 5. Disconnect the SAS unit connector with the ignition off.
* 6. Turn the ignition on and verify that the voltage of each of the following locations is more than 9 V.
Between the terminal B and ground
Between the terminal AB and ground
Between the terminal Z and ground
^ If less than 9 V, inspect the harness, fuse, connector and terminal, then repair the faulty part.
C. Diagnose SAS unit internal problems
^ If no problem is found during the step (1), an SAS unit internal problem may be the cause. Before replacing the SAS unit with a new one, verify, that the warning light illuminates according to the following:
1. Turn the ignition switch to ON, and wait for six seconds.
2. Turn the ignition switch to OFF, then to ON again. Observe the air bag warning light.
^ If the warning light does not illuminate, repeat step 1.
^ If the warning light stays on, replace the SAS unit with a new one.
^ If the air bag warning light flashes six or seven times.
This problem is related to the circuit of either the driver or passenger-side air bag module, and is not caused by the SAS unit.
^ Follow the Troubleshooting Procedure in the Workshop Manual (Section T).
3. Check the air bag module connection on both the driver and passenger sides.
^ Check if the connector terminals are deformed.
^ Check the short bar.
^ Verify that the connector is properly connected.
^ Verify the terminals' positions.
^ Inspect connector for damage.
^ Verify the air bag module part number.