GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 GMC C Sierra - 2WD 🢒 Restraints 🢒 SIR 🢒 DTC P1AC9

Circuit Description

The internal fault detection is handled inside the control module. No external circuits are involved.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1AC9 HCM Service Calibration Fault

Conditions for Running the DTC
    • The module has received voltage on the ignition 0 voltage circuit.
    • The module has turned ON and no configuration DTC are present.
    • This diagnostic shall be run every 100 ms.
    • Reference voltage is stable and accurate.
    • The module microprocessor must be active/awake.

Conditions for Setting the DTC

This DTC indicates that the energy storage control module (ESCM), starter generator control module (SGCM) or heating control module (HCM) has not yet been programmed with latest production software.

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, if equipped, may display a message.
    • The microprocessor reverts back to the base programmed critical operating data until new data is learned and stored in module.

If the SGCM DTC P1A6C is set current, the vehicle will not crank.

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.

Diagnostic Aids
    • This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
    • If this DTC is retrieved as both a current and history DTC, reprogram the module.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Retrieve DTCs.

Is DTC retrieved as a current DTC?

Go to Step 3

Go to Diagnostic Aids

3

Important: Perform the setup procedure for the appropriate module, if required.

Reprogram the appropriate module. Refer to Service Programming System (SPS) .

Did you complete the reprogramming?

Go to Step 4

--

4
  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