The vehicle power mode master (PMM) is the body control module (BCM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination of the power mode. The PMM receives the ignition switch signals, and additionally a reference voltage signal from the BCM, through the ignition switch, and back to the BCM. There are redundancies within the PMM system that can allow operation of certain subsystems when there are faults in the ignition switch circuits. Other information such as serial data input from other modules and DTCs is also used to determine what power mode signals and information is transmitted by the PMM. The BCM logic uses all this information to identify the operator's desired power mode and activate specific discrete signals, and serial data messages for the operation of different subsystems as necessary. Other modules which have switched voltage inputs may operate in a default mode if the PMM serial data message does not match what the individual module can detect from its own connections.

The PMM will activate relays and other direct outputs of the PMM as needed according to the calculated power mode. Some relays controlled by the BCM are switched ignition voltage outputs that are pass through circuits within the BCM directly from the ignition switch. If these circuits short to ground, the B+ circuit fuse to the ignition switch will open.

B1370

The BCM detects that the ignition 1 signal is shorted to ground, voltage, or open.

B1380

The BCM detects that the ignition 3 signal is shorted to ground, voltage, or open.

B1385

The BCM detects that the crank signal is shorted to ground, voltage or open.

A current DTC clears when the malfunction is no longer present.

Schematic Reference

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, access BCM, Power Mode data display list and compare all parameters listed with the corresponding ignition key position. The PMM Power Mode Parameters table below illustrates the correct state of these input parameters in correspondence to the ignition switch position.

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Connect a test lamp between each fuse test terminal of the ignition switch B+ circuit fuse and ground. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the ignition switch circuits listed below for a short to ground. If all circuits test OK, replace the BCM.

•	B+ terminal A, X1 - with LS4

•	B+ terminal 4 - without LS4

•	B+ terminal A, X2 - with LS4

•	B+ terminal 6 - without LS4

•	Ignition terminal B, X1- with LS4

•	Ignition terminal 5 - without LS4

•	Ignition terminal B, X2 - with LS4

•	Ignition terminal 7 - without LS4

•	Ignition terminal C, X2 - with LS4

•	Ignition terminal 3 - without LS4

2. Disconnect the harness connector at the ignition switch.
3. Connect a test lamp between the ignition switch terminals listed below and ground. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

•	B+ terminal A, X1 - with LS4

•	B+ terminal A, X2 - with LS4

•	B+ terminal 4 - without LS4

•	B+ terminal 6 - without LS4

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

4. Perform the ignition switch component test. Verify the switch passes the test.

⇒	If the ignition switch does not test normal, replace the ignition switch.

5. Disconnect the X1 harness connector at the BCM, test for less than 1.0 volt between the circuit terminals of the BCM listed below and ground:

•	12-volt reference terminal 25

•	Ignition terminal 21

•	Ignition terminal 22

•	Ignition terminal 23

⇒	If greater than specified, test the circuit for a short to voltage.

6. Test for less than 1.0 ohm between the BCM and the ignition switch on the circuits listed below:

•	12-volt reference terminal 25, X1 and A, X1 - with LS4

•	12-volt reference terminal 25, X1 and 4 - without LS4

•	12-volt reference terminal 25, X1 and A, X2 - with LS4

•	12-volt reference terminal 25, X1 and 4 - without LS4

•	Ignition terminal 21, X1 and B, X1 - with LS4

•	Ignition terminal 21, X1 and 5 - without LS4

•	Ignition terminal 22, X1 and B, X2 - with LS4

•	Ignition terminal 22, X1 and 7 - without LS4

•	Ignition terminal 23, X1 and C, X2 - with LS4

•	Ignition terminal 23, X1 and 3 - without LS4

⇒	If greater than specified, test the circuit for open/high resistance.

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

Ignition Switch

Using the Resistance Test below, check the resistance between the terminals of the ignition switch listed in each switch position listed.

Perform the Diagnostic Repair Verification after completing the repair.