Chart A History Code Diagnosis

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Wiring Diagram:

***This procedure is updated by TSB 93-9-4, November 1992***

CIRCUIT DESCRIPTION
When the DERM recognizes "Ignition 1" voltage, applied to terminal "A9" and "A10," is in the normal operating voltage range the "AIR BAG" warning lamp is flashed 7 times to verify operation. At this time the DERM performs Turn-ON" tests followed by "Continuous Monitoring" tests. When no malfunctions are detected the DERM proceeds to the "initiator Assembly Resistance Test. When a malfunction is detected the DERM sets a current diagnostic trouble code and illuminates the "AIR BAG" warning lamp. The DERM will clear current diagnostic trouble codes and move them to a history file when the malfunction is no longer detected and/or the ignition switch is cycled except for DTC 51. DTC 51 can only be cleared using a scan tool "Clear Codes" command.

DIAGNOSTIC AIDS
When diagnosing an intermittent DTC 24 ("24 H", indicating History 24), when it is set alone or in combination with any other DTC(s), follow the diagnostic chart of "Current Code 24." However, when diagnosing an intermittent DTC 24, the DERM should NOT be replaced. It is extremely rare for an intermittent problem (History DTC) to be caused by the DERM itself.

DTC 24 can be set by any of the following conditions:
1) A short to ground or B+ on:
- Either SIR Coil Assembly circuit
- CKT 347
- CKT 348
- CKT 349
- CKT 688
- CKT 714
- CKT 752
2) A short to ground on CKT 753
3) An open in CKT 752
4) Improper resistance in the:
- Resistor Module
- Arming Sensor
- Discriminating Sensor(s)


TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Since performing the "SIR Diagnostic System Check" properly ensures correct operation of the "AIR BAG" warning lamp, no malfunction is indicated. SIR Diagnostic System Check
2. Checks for opens in the high side of the deployment loops in shorts to ground in the low side of the deployment loops.
3. Checks for shorts to B+ in the deployment loops.
4. Checks for an improperly connected dual pole arming sensor.
5. Checks for an open in the "Ignition 1" feed to the deployment loops.
6. Checks for a condition which would prevent either "36 VLR" power supply from fully charging. Checks for conditions which the DERM interprets as an open in the "Driver 36 VLR" circuit.
8. Checks for conditions which the DERM interprets as an open in the "Passenger 36 VLR" circuit.
9. Check for an open or high resistance in the driver inflator module circuitry.
10. Checks for an open or high resistance in the passenger inflator module circuitry.
11. Checks for shorts which would cause the resistance of the inflator modules measured by the DERM to be too low.
12. Checks for an open in CKT 348E.
13. Checks for an open in CKT 348B.
14. Checks for shorts from the "36 VLR" circuits to diagnostic circuits or a short which decreases the effective resistance at the high side of the deployment loops.
15. Checks for shorts which the DERM interprets as an open driver ignition diode.
16. Checks for shorts which the DERM interprets as an open passenger ignition diode.
17. Checks for improper connections to the discriminating sensors.
18. Checks for an open or short to ground in the "Driver Source Sense" circuit.
19. Checks for an open or short to ground in the "Passenger Source Sense" circuit.
20. Checks for an open in the "Driver Side Low" circuit.
21. Checks for an open in the "Passenger Side Low" circuit.