DTC 18

Circuit Description
When the ignition switch is turned ON, the sensing and diagnostic module (SDM) will perform tests to diagnose critical malfunctions within itself. Upon passing these tests, Ignition 1 and deployment loop voltages are measured to ensure that they are within their respective normal voltage ranges. The SDM monitors the voltages at the driver low terminal (terminal 3) and the passenger low terminal (terminal 4) to detect shorts to ground in the deployment loops.

DTC 18
DTC 18 will set if the voltage at the passenger low terminal falls below a specified value and Ignition 1 is within the normal operating voltage range.

This test is run during turn-on tests and every 100 milliseconds during continuous monitoring.

When DTC 18 is set, the SDM will turn on the AIRBAG indicator and also set a DTC 71.

DTC 18 will clear when the malfunction is no longer occurring and the SDM has been replaced. DTC 18 cannot be cleared with the scan tool.

Diagnostic Aids
Carefully inspect the wires in the passenger loop for cutting or chafing. If the wiring pigtail of the passenger air-bag is damaged, the passenger airbag must be replaced.

Test Description
The numbers below refer to steps on the diagnostic table.
3. Refer to the first caution below.
4. Refer to the first caution below.
5. Refer to the third caution below.

Steps 1 - 6:

Steps 7 - 8:

DTC 18 - Passenger Deployment Loop Short to Ground

CAUTION: The sensing and diagnostic module (SDM) can maintain sufficient voltage to deploy the airbags for 10 minutes after the ignition is OFF and the fuse has been removed. If the airbags are not disconnected, do not begin service until 10 minutes have passed after disconnecting power to the SDM. Otherwise, injury could result.

CAUTION: Never measure the resistance of an inflator module with an ohmmeter. The ohmmeter battery could unexpectedly deploy the airbag which would created the possibility of severe injury and would require the replacement of otherwise useable components.

CAUTION: During service procedures, be very careful when handling the SDM. Never strike or jar the SDM. Never power the supplemental inflatable restraints (SIR) system when the SDM is not rigidly attached to the vehicle. All SDM mounting bolts must be carefully tightened, and the SDM arrow must be pointing toward the front of the vehicle to ensure proper operation of the SIR system. The SDM could be activated if it Is powered when it is not rigidly attached to the vehicle, resulting in unexpected deployment and possible injury.

Important: A careful inspection of the circuits and components indicated on the DTC 18 chart is essential to ensure that the replacement SDM will not be damaged. When DTC 18 has been set, it is necessary to replace the SDM.