GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) monitors the voltage supplied on the feedback circuit of the engine controls ignition relay or the main relay. Voltage that is out of range will cause incorrect input readings from the engine components connected to the relay. If the ECM detects voltage present on the feedback circuit of the main relay when the ignition is turned OFF, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0563 System Voltage High

Conditions for Running the DTC

    • The ignition is ON.
    • DTC P0563 runs continuously once the above conditions are met.

Conditions for Setting the DTC

    • The ECM detects the ignition voltage is more than 16 volts.
    • The ECM detects voltage on the feedback circuit of the main relay is more than 16 volts for 7.6 seconds.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will not illuminate.
    • The ECM will store conditions which were present when the DTC was set as Failure Records data only.
    • This information will not be stored in the Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

Diagnostic Aids

    • For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .
    • The following table illustrates the MAIN relay terminal location in the underhood fuse block:

Main Relay Terminal Identification

Control

B+ - Coil

Feedback

B+ - Switch

Front of Vehicle

Step

Action

Values

Yes

No

Schematic References: Engine Controls Schematics for the 0.8 L engine or Engine Controls Schematics for the 1.0 L engine

Connector End View References: Engine Controls Connector End Views for the 0.8 L engine or Engine Controls Connector End Views for the 1.0 L engine

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Are DTCs P1610 or P1611 also set?

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Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Clear the DTC with a scan tool.
  3. Turn OFF the ignition for 30 seconds.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the DTC information with a scan tool.

Does DTC P0563 set?

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Go to Step 5

Go to Step 4

4

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

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Go to Step 5

Go to Testing for Intermittent Conditions and Poor Connections

5

  1. Turn OFF the ignition.
  2. Disconnect the main relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the main relay switched output terminal at the fuseblock for the feedback circuit of the relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 7

6

Test all circuits that have voltage supplied by the main relay including the feedback circuit of the relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 11

Go to Step 8

7

Test for shorted terminals or poor connection at main relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 11

Go to Step 9

8

Test for shorted terminals or poor connection at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

9

Replace the main relay.

Did you complete the replacement?

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Go to Step 11

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10

Replace the ECM.

Did you complete the replacement?

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Go to Step 11

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11

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 12

12

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

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Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK