When the ignition switch is first turned ON, the SDM will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1", VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM monitors the voltage at "Driver Side LO" terminal A2 and "Passenger Side LO" terminal A4 to detect shorts in ground in the passenger inflator module circuits.

The VLR power supply in the SDM is in its normal operating range and at least one of the two inflator modules is not open. Then, if the voltage measured at "Driver Side LO" is greater than 3 volts and the voltage measured at "Passenger Side LO" is less than or equal to three volts for 500 milliseconds during "Continuous Monitoring" or "Current Source Diagnostic," DTC1018 will set.

SDM turns ON the AIR BAG telltale lamp and sets DTC B1018 and also B1071. DTC B1018 will take precedence over DTCs B1015,B1016,B1018,B1021 and B1022.

The fault condition is removed and the SDM is replaced. DTC B1018 will remain current, regardless if the ignition switch is turned OFF or a Scan Tool "Clear Codes" command is issued until the faulty wiring or component is repaired or replaced and the SDM is replaced.

It is critical to diagnose all circuitry before replacing the SDM. If the malfunction still exists, the new SDM will be damaged. An intermittent condition is likely to be caused by a short to ground in the passenger inflator module circuits. Inspect circuits 1403 and 1404 carefully for cutting and chaffing. If the wiring pigtail of the passenger inflator module is damaged, the module must be replaced. If no circuit or component failures are located, after a complete and thorough inspection, the fault may have occurred internally to the SDM.

The test for this diagnostic trouble code is run during "Continuous Monitoring" and "Current Source Diagnostics," unless DTC B1017 or B1026 is detected.

When measurements are requested in this chart use SA 91114NE DVM with correct terminal adapter from SA 9206Z. When a check for proper connection is requested refer to Intermittent and Poor Connections in this manual. When a wire connector or terminal repair is requested, use the proper repair parts and refer to Wiring Repairs .

Caution: Be careful when you handle a sensing and diagnostic module (SDM). Do not strike or jolt the SDM. Before applying power to the SDM:

The numbers below refer to the step numbers on the diagnostic table.

1. This test determines whether the malfunction is occurring in the passenger inflator module, or the circuitry.

2. This test checks for a short from "Passenger Side LO" to ground.

3. This test checks for a short from "Passenger Side HI" to ground, or a SDM integrity problem.