SIR DTC 24 Diagnosis

Group Ref.: 9 - Accessories

Bulletin No.: 449001

Date: August, 1994

INFORMATION

SUBJECT:
DIAGNOSING SIR DTC 24 - ALL DERM SYSTEMS

MODELS:
1993 AND PRIOR MODELS WITH SIR
1994-95 MODELS WITH SIR EXCEPT THOSE WITH SENSING AND DIAGNOSTIC MODULE (SDM)

When diagnosing an SIR DTC 24, the following discriminating sensor check should also be performed.

^ UNPLUG DISCRIMINATING SENSOR

^ SENSOR MUST REMAIN BOLTED SECURELY TO VEHICLE CHASSIS.

^ MEASURE RESISTANCE FROM SENSOR PINS TO CHASSIS GROUND. Must be greater than 2 MEG OHMS. IF NOT, THEN REPLACE THE SENSOR.

NOTE:
For intermittent SIR DTC 24 concerns, it may be helpful to water-soak the discriminating sensor before performing the above test.

Experience has shown that discriminating sensors are a leading cause of DTC SIR Code 24 concerns. These sensors can develop two separate conditions that will cause DTC SIR Code 24:

1. The first is caused by a shorted internal resistor and is addressed by current service manual procedures.

2. The second is caused by a partial short between the internal resistor and the sensor case (Ground). This condition is not checked by the service manual procedure.

When used together with the service manual Code 24 diagnostic chart, the above procedure will detect a failed discriminating sensor. Please update your service manuals to reflect this additional check.