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 improper conditions are present, the powertrain control module (PCM) will disable cruise control via the cruise inhibit control circuit. During cruise control, if the engine speed exceeds the calibrated RPM, the PCM will inhibit the cruise control system, and set DTC P1566.

Conditions for Running the DTC

    • The cruise control is enabled.
    • The cruise control is engaged.

Conditions for Setting the DTC

The PCM detects an engine speed more than the 6300 RPM.

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 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 check with the customer for the conditions that set the DTC.

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

Step

Action

Yes

No

1

Did you perform A Diagnostic System Check - Cruise Control?

Go to Step 2

Go to Diagnostic System Check - Cruise Control

2

Are any ABS/TCS DTCs set?

Go to the ABS/TCS DTCs first

Go to Step 3

3

Are any Transaxle DTCs set?

Go to the Transaxle DTCs first

Go to Step 4

4

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

Did an engine RPM condition cause this DTC to set?

Go to Step 5

Go to Diagnostic Aids

5

Explain system operation to the customer and clear this DTC.

Is the action complete?

System OK

--