GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 DTC P0A27 or P1A58

Circuit Description

The ESCM will monitor the battery cut off switch for over voltage or an open.

Conditions for Running the DTC
    • Engine is running for 30 seconds.
    • The ESCM has turned ON and no configuration DTC is present.
    • This diagnostic shall run every 100 milliseconds.
    • Reference voltage is stable and accurate.

Conditions for Setting the DTC
    • P0A27 - Battery cut off switch status is greater than 5.35 volts.
    • P1A58 - The ESCM senses that the battery cut off switch is open.

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.

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: Starting and Charging Schematics

Connector End View Reference: Engine Electrical Connector End Views

1

Was the Engine Electrical Diagnostic System Check performed?

Go to Step 2

Go to Diagnostic System Check - Engine Electrical

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 ESCM DTC list.

Is the DTC set as current DTC?

Go to Step 4

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

3

Test the BCO Status circuit of the battery cut off switch for a short to voltage above 5.5 volts or an open. Refer to Circuit Testing Circuit Testing and Wiring Repairs Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4

Inspect for poor connections at the harness connector of the battery cut off switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 5

5

Replace the battery cut off switch. Refer to Battery Service Disconnect Switch Replacement .

Did you complete the replacement?

Go to Step 6

--

6
  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