GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Classic - 4WD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 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.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1A87 Low Starter/Generator Control Module Coolant Level

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: Hybrid Cooling Schematics

Connector End View Reference: Hybrid Cooling 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

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

Did you complete the replacement?

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