GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P1A26: Hybrid Battery 1 Voltage Low

DTC P1A27: Hybrid Battery 1 Voltage Very Low

Circuit/System Description

The battery energy control module (BECM) monitors the hybrid battery 1 voltage to detect if the minimum voltage is less than the calibration value.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P1A26

Minimum module voltage is less than calibration value for 3 seconds.

P1A27

Minimum module voltage is less than calibration value for 40 ms.

Action Taken When the DTC Sets

The hybrid system is disabled.

Conditions for Clearing the DTC

P1A26, P1A27

System voltage 11-18 volts.

Reference Information

Schematic Reference

Hybrid Energy Storage Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Generator Battery Carrier Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

P1A26, P1A27

  1. If other DTCs are set diagnose those first.
  2. These DTCs are for information only. The DTCs can set in cold weather. Clear the DTC, no diagnostic or removal/replacement procedures are required.