Chart A1 History Code Diagnosis

Diagnosis Chart:

Electrical Chart:

***This Procedure has been Updated by TSB 93-U-10, December 1992***

DESCRIPTION
When the Ignition Switch is first turned "ON" system voltage is applied through Fuse #6 to the "SIR Indicator High" input (B9) and the "INFLATABLE RESTRAINT" warning lamp which is connected to "SIR Indicator Low" input (A 1). Fuse #7 also applies system voltage to the "IGNITION 1" inputs (A3 and B3). The DERM responds by blinking the "INFLATABLE RESTRAINT" warning lamp 7 to 9 times.

When the engine is being cranked system voltage is applied to the DERM at the "CRANK" input. The DERM grounds the warning lamp circuit until system voltage is removed from the "CRANK" input. This results in a steady "INFLATABLE RESTRAINT" warning lamp during cranking.

After cranking, the DERM again blinks the "INFLATABLE RESTRAINT" warning lamp 7 to 9 times

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)

NOTES ON FAULT TREE
1. The DERM determines that the Arming Sensor is closed when system voltage or more is present at the Sense Hi input, and it determines that a Discriminating Sensor is closed when it notes low voltage at the Sense Low input. There are some faults that can "look" like an accident to the DERM, and therefore record a DTC 51. History DTC 51 therefore is not proof that the vehicle was in an accident.
2. When a history DTC 51 is set, history DTC 34 does not set. Therefore, any conditions which causes a current DTC 34 to set does not set a history DTC 34 when a history DTC 51 is set. When the "INFLATABLE RESTRAINT" warning "lamp alerts the owner intermittently of a current DTC and no corresponding history DTCs are set, the most likely cause is an intermittent open in circuit 1139.
3. Checks for intermittent electrical conditions within the steering column.
4. Checks for intermittent shorts in the 36VLR wiring (circuit 236).
5. Checks for burned or misinstalled Fuse #6 and "INFLATABLE RESTRAINT" warning lamp bulb or uncleared DTC 61 after a completed wiring repair on circuit 349. Also checks for intermittent faults in circuits 688 and 358.
6. Checks for intermittent opens in the ground path of the deployment loop between the base of the steering column and both Discriminating Sensors (circuit 348, 349 and 1003).