Power Mode: Notes

WARNING: This page is about a different car, the 2006 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the instrument panel module (IPM). The IPM will monitor the ignition mode switch only with battery voltage above 7 volts to prevent invalid input readings during low voltages encountered during vehicle cranking. If the ignition mode switch input or the battery voltage input changes, a ratio metric calculation of ignition mode switch input value is performed. The IPM discerns the following states over the ignition mode switch signal circuits:

Switch inactive
Switch stuck
Start button active
Off/Acc button active
Ignition mode switch signal circuit short to ground
Ignition mode switch signal circuit short to B+

To determine the correct power mode the IPM uses:

The ignition mode switch data received from the ignition mode switch
The status of the engine run flag (ERF)

The following power modes are transmitted on both low speed and high speed GMLAN serial data circuits:

Off-Awake
Accessory
Run
Crank

The accessory power mode times out after 20 minutes and the power mode becomes Off-Awake.

The following outputs are controlled by IPM as part of the power moding task:

Accessory voltage, active in Accessory and Run power modes.
Run Ignition 3 voltage, active in a remote start request and in Run power mode.
Run/Crank Ignition 1 voltage, active in a remote start request and in Run and Crank power modes.
Engine control module (ECM)/transmission control module (TCM) serial data wake-up, active in a remote start request and in all power modes when IPM is awake except Crank.
High speed GMLAN serial data wake up, active in a remote start request and in all power modes when IPM is awake.