Air Bag Systems

DTC 18

CIRCUIT DESCRIPTION
The steering wheel module deployment loop consists of a inflatable restraint steering wheel module, an inflatable restraint steering wheel module coil, the steering wheel module high and steering wheel module low circuits. A shorting bar is used in the inflatable restraint steering wheel module and the inflatable restraint steering wheel module coil connectors which will short together the steering wheel module high and steering wheel module low circuits when the connector is disconnected, this will help to prevent unwanted deployment of the inflator module during servicing. During a frontal crash of sufficient force the sensing and diagnostic module (SDM) will allow current to flow through the deployment loop in order to deploy the inflatable restraint steering wheel module. The SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a DTC will be stored.

CONDITIONS FOR RUNNING THE DTC
Ignition voltage is within the normal operating voltage range.

CONDITIONS FOR SETTING THE DTC
- DTC 17 will set when the SDM detects a short to voltage in the steering wheel module deployment loop.
- DTC 18 will set when the SDM detects a short to ground in the steering wheel module deployment loop.

ACTION TAKEN WHEN THE DTC SETS
The SDM commands the AIR BAG indicator ON.

CONDITIONS FOR CLEARING THE DTC
The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

DIAGNOSTIC AIDS
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:
- A short to voltage in the steering wheel module high or the steering wheel module low circuits
- A short to ground in the steering wheel module high or the steering wheel module low circuits
- An internal SDM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION

Step 1 - 4:

Step 5 - 13:

The numbers below refer to the step numbers on the diagnostic table.
4. Test the steering wheel module high and the steering wheel module low circuits for a short to voltage.
8. Test to see if the malfunction is caused by the inflatable restraint steering wheel module.
9. Test the steering wheel module high and the steering wheel module low circuits for a short to ground.