DTC 18

CIRCUIT DESCRIPTION

When the ignition is switch is turned to "RUN," the SDM will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1" 23 VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM monitors the voltages at "Driver Side Low" terminal "3" and "Passenger Side Low" terminal "4". to detect shorts to ground in the inflator module circuits. The service wait time is 10 minutes. Refer to "Arming and Disarming Air Bag(s)" for enable/disable procedures before replacing SIR components.

DTC WILL SET WHEN

Neither of the two inflator module circuits is open. "Ignition 1" voltage is within the normal operating range. The voltage of both "Driver Side Low," and "Passenger Side Low" are NOT below a specified value. Once these conditions are met and the voltage at "Passenger Side Low" is below a specified value. DTC 18 is set. This test is run during "Turn-ON" tests and every 100 milliseconds during "Continuous Monitoring."

ACTION TAKEN

SDM turns "ON" the "AIR RAG" warning lamp and sets DTC 18 and also DTC 71.

DTC WILL CLEAR WHEN

The malfunction is no longer occurring (has been repaired) and the SDM has been replaced. DTC 18 is a latched code and cannot be cleared.

DTC CHART TEST DESCRIPTION

Numbers below refer to circled numbers on the diagnostic chart.

1. Monitoring "Pass. Senselo" may help to locate the fault. The value displayed by the TECH 1 is updated continuously so that intermittent shorts can be located by moving wires while monitoring "Pass. Senselo."

2. This test checks for a malfunctioning passenger inflator module.

3. This test determines whether the malfunction is in CKT 1403.

4. This test determines whether the malfunction is in CKT 1404.

DIAGNOSTIC AIDS

An intermittent condition is likely to be caused by a short to ground in the passenger inflator module circuit. Inspect CKTs 1403 and CKT 1404 carefully for cutting or chafing. If the wiring pigtail of the passenger inflator module is damaged the component must be replaced. A careful inspection of the circuits and components indicated on the DTC 18 chart including the passenger module module pigtail is essential to ensure that the replacement SDM will not be damaged.