Part 1 of 2

Test R: DTC 28 Current Sink Or Source Failure (Part 1 Of 2):

Supplemental Inflatable Restraint (SIR):

OPERATION:
During the "Initiator Assembly Resistance Test" the DERM grounds the "Passenger Side Low" terminal "B7" and turns "ON" the driver current source at the "Driver Side High" terminal "B9" The DERM then grounds the "Driver Side Low" terminal "B8" and turns "ON" the passenger current source at the "Passenger Side High" terminal "A7." During each of these tests. the DERM monitors voltage at "Driver Side Low", "Passenger Side Low", the difference between "Driver Side High" and "Driver Side Low" and the difference between "Passenger Side High" and "Passenger Side Low." When the measured values are outside the expected range, DTC 28 is set.

Test Conditions: Tested once each ignition cycle during the "Initiator Assembly Resistance Test" when: 1) No "higher priority faults" are detected during "Turn-ON", 2) No "higher priority faults" are detected during "Continuous Monitoring" for 1 second, 3) No "CRANK" Signal present, 4) "Ignition 1" voltage is above a specified value.

Failure Conditions: DTC 28 will set when the voltage measured at "Driver Side Low" or "Passenger Side Low" is below a specified value while its respective initiator resistance is in range or when the voltage measured at "Driver Side Low" or "Passenger Side Low" is above a specified value.

Action Taken: The DERM turns "ON" the "INFLATABLE RESTRAINT" warning lamp and sets a Diagnostic Trouble Code.

Conditions to Clear: DTC 28 will clear each time the ignition switch is turned "OFF."

POSSIBLE CAUSES:
Test Description: Number(S) below refer to circled number(S) on the diagnostic chart.
1. This test checks if the malfunction is in the Forward Discriminating Sensor.
2. This test determines if the malfunction is in circuit 1404B.
3. This test determines whether the malfunction is in the RH Mid-Rail Discriminating Sensor.

DIAGNOSTIC AIDS:
An intermittent condition is likely to be caused by a poor connection to the forward discriminating sensor terminals "A" and "B," the RH mid-rail discriminating sensor terminals "A" and "B," or poor wire to terminal connection in CKT 1404B. When a scan tool "Clear Codes" command is issued and the malfunction is still present, the DTC will not reappear for 10 minutes or until the next ignition cycle. For additional information, refer to Diagnostic Aids for Test R (part 2 of 2). Part 2 of 2