The body control module (BCM) monitors the ignition inputs Ignition Off/Run/Crank, Ignition 1 Run/Crank and the Ignition Accessory signals supplied from the ignition switch. The BCM uses the sequence that the signals appear, their voltage levels and the engine run flag (ERF) status to determine the power mode. Battery voltage is supplied to the ignition switch by a fuse in the underhood fuse block. In addition, the BCM supplies the ignition switch a 5-V reference signal that the ignition switch uses for the output to the BCM on the off/run/crank voltage circuit. The off/run/crank voltage circuit supplies voltage to the BCM for theft purposes.

B+ is between 9-16 V.

B1442

The BCM detects that the Off/Run/Crank signal is open or shorted to ground.

B1443

The BCM detects that the Off/Run/Crank signal is shorted to voltage.

Schematic Reference

Power Distribution Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Mode Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for Scan Tool Information

With a scan tool, observe the Ignition Accessory parameter and compare the parameter to the Correct Ignition Switch Inputs table with the corresponding ignition key position. The Correct Ignition Switch Inputs table illustrates the correct state of these input parameters (circuits) in correspondence to the ignition switch position.

Important: The ignition switch component test must be preformed before proceeding with this test to verify the integrity of the switch.

1. Perform the ignition switch component test. The test should pass.

⇒	If the ignition switch fails, replace the ignition switch.

2. Ignition OFF, disconnect the X2 harness connector at the BCM. Connect the harness connector at the ignition switch.
3. Verify that a test lamp does not illuminate between ground and the off/run/crank voltage circuit terminal A14.

⇒	If the test lamp illuminates, test the following ignition switch circuits for a short to voltage:

•	5-V reference

•	Of/run/crank voltage

4. Verify that a test lamp does not illuminate between B+ and the off/run/crank voltage circuit terminal A14.

⇒	If the test lamp illuminates, test the following ignition switch circuits for a short to ground:

•	5-V reference

•	Of/run/crank voltage

5. Ignition ON, test for less than 1.0 Ω on the off/run/crank voltage circuit between BCM connector terminal A14 and terminal A42.

⇒	If greater than the specified range, test the following ignition switch circuits for open/high resistance.

•	5-V reference

•	Of/run/crank voltage

6. If all circuits test normal, replace the BCM.

Ignition Switch

1. Ignition OFF, disconnect the harness connector at the ignition switch.
2. Using the Resistance Test table below, check the resistance between the terminals of the ignition switch listed in each switch position.

Perform the Diagnostic Repair Verification after completing the repair.