Supplemental Inflatable Restraint (SIR)

CIRCUIT DESCRIPTION
The steering column circuit consists of the inflator module, SRS coil assembly, center sensor assembly and associated wires. The center sensor assembly injects a small amount of current through the steering column circuit through the D+CKT output, terminal "B8." By monitoring the voltage at the D- CKT input, terminal "B7," the center sensor assembly calculates the combined resistance of the inflator module, SRS coil assembly and their associated wiring.

FAILURE CONDITIONS
DTC 12 will set if the center sensor assembly detects a short to B+ in the steering column circuit, a short to B+ in the forward sensor circuits or opens in both forward sensor circuits. An open only in one forward sensor circuit will set a DTC 15.

ACTION TAKEN
The center sensor assembly will illuminate the air bag indicator and open the safety circuit, disabling the SRS.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test determines whether the fault is in the steering column components or in the SRS circuitry.
2. This test checks for a short to B+ in the D+ CKT.
3. This test determines whether the steering column fault is due to a faulty SRS coil assembly or a faulty inflator module.
4. This test checks for a short to B+ in the D- CKT.
5. This test checks for opens in both forward sensor circuits.
6. This test checks for a short to B+ in the SR+ CKT.
7. This test determines whether the fault is due to a short to B+ in the SL+ CKT or a faulty center sensor assembly.