GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The purpose of the accessory power module (APM), integral to the starter/generator control module (SGCM), is to control the amount and direction of energy flowing between the 42 V DC and 14 V DC buses via the APM, bi-directional 42 V DC to 14 V DC converter. All APM functions will only be run when in the enable mode. APM current will be defined as the current flowing through the outputs. APM power is bi-directional, with negative current representing 14-42 direction, and positive current representing the 42-14 direction.

When the APM power conversion direction is set to a value of 42 V to 14 V, the energy will flow from the 42 V DC Bus to the 14 V DC Bus via the APM. When the service charge or jump starting is requested, the energy will flow from the 14 V DC Bus to the 42 V DC Bus via the APM. When the APM power conversion direction is set to a value of Off, the APM will be turned OFF, and not consume or transfer any power. When the APM power conversion direction is set to a value of Invalid, the energy will flow from the 42 V DC Bus to the 14 V DC Bus via the APM.

The following DTCs are for internal failures within the SGCM.

    • P1AB2 is hybrid system voltage.
    • P1A64 is for SGCM reset.
    • P1A65 is SGCM long term memory performance.
    • P1A66 is SGCM loop overrun.
    • P1A67 is SGCM options incorrect.
    • P1A68 is failed SGCM programming read only memory (ROM).
    • P1A69 is failed SGCM programming random access memory (RAM).
    • P1A6A is failed SGCM read only memory (ROM).
    • P1A6B is failed SGCM 5-volt reference circuit.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC P1AB2 Hybrid System Voltage
    • DTC P1A64 Starter/Generator Control Module Reset
    • DTC P1A65 Starter/Generator Control Module Long Term Memory Performance
    • DTC P1A66 Starter/Generator Control Module Loop Overrun
    • DTC P1A67 Starter/Generator Control Module Options Incorrect
    • DTC P1A68 Starter/Generator Control Module Programming Read Only Memory (ROM)
    • DTC P1A69 Starter/Generator Control Module Random Access Memory (RAM)
    • DTC P1A6A Starter/Generator Control Module Read Only Memory (ROM)
    • DTC P1A6B Starter/Generator Control Module 5-Volt Reference Circuit

Conditions for Running the DTC

    • Engine running for 30 seconds
    • The SGCM has received voltage on the ignition 0 voltage circuit.
    • The SGCM has turned ON and no configuration DTC are present.
    • This diagnostic shall be run every 100 ms.
    • Reference voltage is stable and accurate.

Conditions for Setting the DTC

    • P1AB2 is 42-volt correlation fault within the SGCM.
    • P1A64 is for energy storage control module (ESCM) and SGCM is abnormally reset.
    • P1A65 is SGCM long term memory performance.
    • P1A66 is SGCM loop overrun.
    • P1A67 is SGCM options incorrect.
    • P1A68 is electrically erasable programmable read-only memory (EEPROM) malfunction was detected. EEPROM is not equal to the checksum stored in EEPROM at power down.
    • P1A69 is failed SGCM programming random access memory (RAM).
    • P1A6A is failed SGCM read only memory (ROM).
    • P1A6B is one or both of the reference range voltages are out of range.

Action Taken When the DTC Sets

    • The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The driver information center (DIC), if equipped, may display a message.

Conditions for Clearing the DTC

    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Step

Action

Yes

No

Schematic Reference: Hybrid Controls Schematics

Connector End View Reference: Hybrid Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
  2. With a scan tool observe the starter/generator control module (SGCM) DTC list.

Is the DTC set as current DTC?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

Inspect for poor connections at the harness connector of the SGCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 5

Go to Step 4

4

Replace the SGCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 5

--

5

  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK