GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) checks the system voltage to make sure that the voltage stays within the proper range. Damage to components, and incorrect input can occur when the voltage is out of range. The ECM monitors the system voltage over an extended length of time. If the ECM detects an excessively low system voltage, DTC P0562 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0562 System Voltage Low

Conditions for Running the DTC

    • Engine speed above 1,500 RPM
    • System voltage between 9.5-18 volts

Conditions for Setting the DTC

The ECM detects a system voltage below 10 volts for 5 seconds.

Action Taken When the DTC Sets

    • The ECM will command a message to be displayed.
    • 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.
    • The DTC can be cleared by using the scan tool Clear DTC Information function.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics for the 4.6L (LH2) engine or Engine Controls Schematics for the 3.6L (LY7) engine

Connector End View Reference: Engine Control Module Connector End Views for the 4.6L (LH2) engine, Engine Control Module Connector End Views for the 3.6L (LY7) engine, or Power and Grounding Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Start the engine.
  3. Raise the engine speed above 1,500 RPM.
  4. With a scan tool, observe the Ignition 1 Signal parameter in the engine control module (ECM) data list.

Does the scan tool indicate that the Ignition 1 Signal parameter is greater than the specified range?

10.5 V

Go to Step 6

Go to Step 3

3

Using a scan tool, compare the Battery Voltage Signal parameter in the dash integration module (DIM) data list with the Ignition 1 Signal parameter in the ECM data list.

Are the Battery Voltage and Ignition 1 Signal parameter readings different by more than the value specified?

0.5 V

Go to Step 4

Go to Charging System Test

4

Test the battery positive voltage circuit of the ECM for a high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 7

Go to Step 5

5

Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

6

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

Did you complete the replacement?

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Go to Step 7

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7

  1. Review and record the scan tool Fail Records data.
  2. Use the scan tool in order to clear the DTC.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
  4. Using the scan tool, observe the Specific DTC Information for DTC P0562 until the test runs.

Does the scan tool indicate that DTC P0562 failed this ignition?

--

Go to Step 2

System OK