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 Descriptor

DTC P0562: System Voltage Low - ECM

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

B+

P0562

P0562

--

--

Ground

--

P0562

--

--

Typical Scan Tool Data

Ignition 1 Signal - ECM

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON, engine OFF.

Parameter Normal Value: 12.6 Volts

Ignition

0.0 Volts

0.0 Volts

12.6 Volts

Circuit/System Description

The engine control module (ECM) monitors the system voltage to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range. If the ECM detects low system voltage, DTC P0562 sets.

Conditions for Running the DTC

    • The vehicle speed is greater than 8 km/h (5 mph).
    • The system voltage is between 9.5-18 volts.

Conditions for Setting the DTC

The ECM detects that the system voltage is less than 10 volts for 5 seconds.

Action Taken When the DTC Sets

    • The ECM will command the charge indicator to be illuminated on the instrument panel cluster (IPC).
    • The ECM will not illuminate the malfunction indicator lamp (MIL).
    • The ECM will store conditions, which were present when the DTC set as Fail Records data only.

Conditions for Clearing the DTC

    • The ECM will command the message OFF after one trip in which the diagnostic test has been run and passed.
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

Diagnostic Aids

    • A low voltage DTC in multiple modules indicates a concern in the charging system.
    • Inspect the ECM gound connection G103 to ensure that they are clean and tight.

Reference Information

Schematic Reference

    •  Starting and Charging Schematics
    •  Engine Controls Schematics

Connector End View Reference

Engine Control Module Connector End Views

Electrical Information Reference

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

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

  1. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.6 and 15.0 volts.
  2. If not within the specified range, refer to Charging System Test .
  3. Observe the scan tool ECM Ignition 1 Signal parameter. The reading should be between 12.6 and 15.0 volts.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connectors at the ECM.
  2. 2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 ohms between the ground circuit terminals and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminals and ground.
  5. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminals and ground.
  7. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  8. If all circuits test normal, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming.