Chart 2

Code 21 (Chart 2):

DERM Circuit Detail:

DESCRIPTION:

The DERM injects a current of 75 milliamperes through the steering column from the Force Hi output (terminal A4) to the Force Low input (terminal A10). By monitoring the voltage at the Sense Hi input (terminal A7) and the Sense Low input (terminal A6) the DERM calculates the combined resistance of the Inflator Module, SIR Coil and connector terminal contact in the steering column. Code 21 will set if the resistance is greater than a specified value or the 100 ohm resistor within the Resistor Module is shorted.

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.

FAILURE CONDITIONS:

Code 21 will set if the combined resistance of the Inflator Module, SIR Coil, harness wiring and connector terminal contact in the steering column is greater than a specified value.

CONDITIONS TO CLEAR:

Current Code 21 will be cleared each time the Ignition Switch is turned OFF.

ACTION TAKEN:

DERM turns ON the "INFLATABLE RESTRAINT" indicator lamp.

NOTES ON FAULT TREE:

1. Checks for short to voltage on CKT 753.

2. Checks for open circuit in CKT 347B or CKT 348B.

3. Determines if open circuit is in CKT 347B or CKT 348B.

4. Checks 100 ohm resistor in resistor module.