GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Cooling 🢒 DTC P1A87

Circuit Description

The starter/generator control module (SGCM) electronics are immersed in an internal fluid to distribute the heat of the electronics evenly through the SGCM, this electronics internal fluid is not the coolant that is circulated through the SGCM cooling system. The SGCM monitors 4 separate coolant level sensors to determine if the electronics internal fluid level is low.

Conditions for Running the DTC
    • The engine has been 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.

Conditions for Setting the DTC

All internal fluid level sensors are indicating a low internal fluid level.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, 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.

Diagnostic Aids

If the vehicle is on an extreme angle this DTC may set.

Step

Action

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

1

Was the Engine Cooling Diagnostic System Check performed?

Go to Step 2

Go to Diagnostic System Check - Engine Cooling

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 SGCM DTC list.

Is the DTC set as current DTC?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

Important: Perform the programming procedure for the SGCM.

Replace the SGCM. Refer to Generator Control Module Replacement in Engine Electrical.

Did you complete the replacement?

Go to Step 4

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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