Chart 1

Diagnosis Chart:

Electrical Chart:

TEST CONDITIONS
Tested once each ignition cycle during the "Steering Column Resistance Test" if: 1) No faults are detected during "Turn-on"; 2) No faults are detected during "Continuous Monitoring" for 1 second; 3) No Crank signal present; 4) "IGNITION 1" voltage is present.

FAILURE CONDITIONS
DTC 21 sets when the combined resistance of the Inflator Module, SIR Coil, Resistor Module, harness wiring and connector terminal contact in the steering column is greater than a specified value.

CONDITIONS TO CLEAR
Current DTC 21 clears each time Ignition Switch is turned "OFF" and the fault is corrected.

ACTION TAKEN
DERM turns on "INFLATABLE RESTRAINT" warning lamp.

DESCRIPTION
The DERM injects a 75 milliampere current through the steering column from the Force Hi output (terminal A4) to the Force Low input (terminal A10). The DERM monitors the voltage at the Sense Hi input (terminal A7) and the Sense Low input (terminal A6) and calculates the combined resistance of the Inflator Module, SIR Coil, Resistor Module, harness wiring (circuits 347, 348 and 349) and connector terminal contact in the steering column. DTC 21 sets when the resistance is greater than a specified value.

NOTES ON FAULT TREE
1. Checks if fault is in steering column. SIR Load Tool J 37808 simulates resistance of good steering column wiring and components.
2. Determines if fault is in Inflator Module or SIR Coil. SIR Load Tool J 37808 simulates resistance of a good Inflator Module.
3. Checks the integrity of Resistor Module's 430 ohm resistor and associated circuitry.
4. Checks for a short between Sense Hi and Force Hi circuits.
5. Checks for short to voltage on circuit 753.