GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The cruise control module uses the cruise engaged circuit to request cruise control. If any condition exists that would make cruise control operation undesirable, the PCM will disable cruise control through the cruise inhibit control circuit.

Conditions for Running the DTC

    • Cruise control is enabled.
    • Cruise control is engaged.

Conditions for Setting the DTC

The PCM detects an engine speed greater than 6300 RPM with the cruise control still engaged.

Action Taken When the DTC Sets

    • The PCM disables cruise control.
    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM will store conditions which were present when the DTC set as Fail Records data only.

Conditions for Clearing the DTC

    • 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's Clear DTC Information function.

Diagnostic Aids

This diagnostic trouble code (DTC) is an information DTC only. The DTC indicates the reason that the PCM disabled the cruise control system. Be sure to verify the conditions that set the DTC with the customer.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may assist in diagnosing the condition. This information may help determine how often the condition that set the DTC occurred.

Step

Action

Yes

No

Schematic Reference: Cruise Control Schematics

1

Did you perform the Cruise Control Diagnostic System Check ?

Go to Step 2

Go to Diagnostic System Check - Cruise Control

2

Since most occurrences of DTC P1566 are caused when the engine speed exceeds the maximum allowed RPM, verify the conditions under which the DTC set with the customer.

Did an engine RPM condition cause this DTC to set?

Go to Step 3

Go to Diagnostic Aids

3

Explain system operation to the customer and clear this DTC.

Is the action complete?

System OK

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