Circuit Description
The ignition key contains a transponder that transmits a signal to the theft deterrent module when the ignition switch is turned to the ON position. The theft deterrent module compares the signal from the key and determines if an authorized key is being used. During this period, the engine control module (ECM) turns on the malfunction indicator lamp (MIL) by grounding the control circuit. The MIL control circuit is monitored by the theft deterrent module. When the theft deterrent module senses the voltage change from the ECM grounding the MIL control circuit, the theft deterrent module switches the signal on the VSS/theft deterrent signal circuit from the speed signal to send the frequency code to the ECM. The theft deterrent module sends the frequency code to the ECM on the same circuit used to transmit vehicle speed information to the ECM. The ECM compares the frequency code with the learned frequency code. If the frequency code sent by the theft deterrent module matches the frequency code programmed in the ECM, the ECM allows the engine to start. If the codes do not match, the ECM disables the injectors to prevent the engine from starting.
Conditions for Running the DTC
The engine is cranking.
Conditions for Setting the DTC
The ECM has not received the frequency code from the theft deterrent module.
Action Taken When the DTC Sets
The ECM will not illuminate the malfunction indicator lamp (MIL).
The engine will not start or may start and stall.
Conditions for Clearing the MIL/DTC
| • | The DTC clears after forty consecutive warm-up cycles if no failures report by this diagnostic or any other non-emission related diagnostic. |
| • | The scan tool clears the MIL/DTC. |
Diagnostic Aids
The theft deterrent module will diagnose an open, short to ground or a short to voltage on the VSS/theft deterrent signal circuit. Any faults on this circuit will set a DTC P1502 in the ECM. An inoperative theft deterrent module will also set a P1502. Refer to the diagnostic procedures in Theft Deterrent in order to diagnose these conditions.
Use the J 35616 connector test adapter kit for any test that requires probing the ECM harness connector or a component harness connector.
Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for the intermittents.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Theft Deterrent System Schematics | ||||
1 | Did you perform the Theft Deterrent Diagnostic System Check? | -- | Go to Step 2 | |
Check for a poor connection at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 4 | Go to Step 3 | |
3 |
Important: This vehicle is equipped with a theft deterrent system that interfaces with the ECM. Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle.
Did you complete the replacement? | -- | Go to Step 4 | -- |
4 |
Does the DTC reset? | -- | System OK | Go to Step 2 |
