Normal vehicle class 2 communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by the power mode master (PMM) module in order to determine the correct power mode. The PMM communicates the system power mode to all class 2 modules on the class 2 serial data line. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.
The numbers below refer to the step numbers on the diagnostic table.
This step tests for battery voltage on the signal circuits that are not required.
This step tests for no battery voltage on the required signal circuits.
If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
This step eliminates open circuits as the cause of the malfunction.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Body Control System Schematics Connector End View Reference: Computer/Integrating Systems Connector End Views Important:: Open the driver door and leave it open during this test. This will disable the retained accessory power (RAP) mode and eliminate this power mode from the power mode parameter list. DEFINITION: This table is used if the observed vehicle power mode does not match the ignition switch position. | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 3 | Go to Step 7 |
3 |
Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 4 | Go to Step 7 |
4 |
Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 5 | Go to Step 7 |
5 |
Important:: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.
Does the displayed power mode parameter match the actual ignition switch position? | Go to Step 6 | Go to Step 7 |
6 |
Does the displayed power mode parameter match the actual ignition switch position? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 7 |
Important:: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.
Is voltage present on only the inputs specified for the ignition switch position? | Go to Step 8 | Go to Step 9 | |
Important:: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.
Is voltage not present on any inputs specified for the ignition switch position? | Go to Step 10 | Go to Step 12 | |
Did you find and correct the condition? | Go to Step 15 | Go to Step 11 | |
Did you find and correct the condition? | Go to Step 15 | Go to Step 11 | |
11 | Inspect for poor connections and terminal tension at the harness connector of the ignition switch. 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 15 | Go to Step 13 |
12 | Inspect for poor connections and terminal tension at the harness connector of the PMM. 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 15 | Go to Step 14 |
13 | Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 15 | -- |
14 | Replace the PMM. Refer to Computer/Integrating Systems Connector End Views for replacement, setup, and programming. Did you complete the replacement? | Go to Step 15 | -- |
15 |
Important:: The engine may start during this procedure. Turn the ignition OFF after verifying all power modes.
Does the displayed power mode parameter match the actual ignition switch position? | System OK | Go to Step 2 |