P1678

DTC P1678

CIRCUIT DESCRIPTION
After the ignition switch is turned to the ON position, and the powertrain interface module (PIM) has authenticated the body control module (BCM), the PIM sends an encrypted security code to the engine control module (ECM). The ECM compares the received security code with its own security code, and if it is valid, the ECM enables the vehicle to be started. If the security code received by the ECM is incorrect, DTC P1678 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P1678 Immobilizer Powertrain Identification Failed

CONDITIONS FOR RUNNING THE DTC
Conditions for running the DTC are:
- The ignition is switched ON.
- The ignition voltage is 10-16 volts.

CONDITIONS FOR SETTING THE DTC
The ECM does not receive a valid response from the PIM when an attempt is made to start the engine.

ACTION TAKEN WHEN THE DTC SETS
When the DTC sets, the following action is taken:
- The vehicle will not start during the current ignition cycle.
- An immobilizer failed message is displayed on the instrument cluster multifunction display.

CONDITIONS FOR CLEARING THE DTC
Refer to Diagnostic General Descriptions for information on the conditions for clearing DTCs.

DIAGNOSTIC AIDS
Refer to Cruise Control Description and Operation for cruise control switch description, operation and inspection procedures. Refer to Cruise Control Schematics, Cruise Control Component Views, and Cruise Control Connector End Views. Refer to Testing for Intermittent Conditions and Poor Connections for intermittent fault conditions.

TEST DESCRIPTION

Step 1 - Step 9:

4. This step tests if the PIM and ECM have been linked together.
5. This step ensures there are no problems within the ECM system that may cause DTC P1678 to set.
6. This step tests the PIM ground circuits and supply voltage.
7. This step tests the PIM harness connector for serviceability.