GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 DTC 🢒 DTC P0506 or P0507

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 Descriptors

DTC P0506: Idle Speed Low

DTC P0507:  Idle Speed High

Circuit/System Description

The throttle actuator control (TAC) motor is controlled by the engine control module (ECM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the ECM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the ECM commands the throttle plate open allowing more air to pass the throttle plate.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0122, P0123, P0128, P0171, P0172, P0174, P0175, P0201-P0208, P0220, P0222, P0223, P0300, P0301-P0308, P0336, P0440, P0442, P0443, P0446, P0452, P0453, P0496, P0502, P0503, P0641, P0651, P1514, P1516, P2101, P2135, P2176 are not set.
    • The engine has been running for at greater than 60 seconds.
    • The engine coolant temperature (ECT) is greater than -15°C (5°F).
    • The AC mode has not changed.
    • The power steering load has not changed
    • The transmission gear sensor switch has not changed.
    • The intake air temperature (IAT) is greater than -18°C (0°F).
    • The barometric pressure (BARO) is greater than 72 kPa.
    • The system voltage is between 10.5-18 volts.
    • The engine is at a stable idle for greater than 2 seconds.
    • These DTCs run continuously when the above conditions are met.

Conditions for Setting the DTC

P0506

    • The actual idle speed is approximately 100 RPM lower than the desired idle speed.
    •  The above condition is present for 15 seconds.

P0507

    • The actual idle speed is approximately 100 RPM greater than the desired idle speed.
    •  The above condition is present for 15 seconds.

Action Taken When the DTC Sets

DTCs P0506 and P0507 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0506 and P0507 are Type B DTCs.

Diagnostic Aids
    • A stalling condition can cause DTC P0506 to set.
    • An intermittent vehicle speed sensor (VSS) signal can cause DTC P0507 to set.
    • An intermittent clutch pedal position sensor signal, if equipped, can cause DTC P0506 to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Throttle Actuator Control (TAC) System Description

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Important: The engine must first be running for greater than 60 seconds, then idle at a steady state for an additional 10 seconds before comparing the actual and desired engine idle speed parameters.

  1. Verify that no other DTCs are not set. If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Compare the desired engine idle speed to the actual engine idle speed with a scan tool. Actual engine idle speed should be no greater than or less than 100 RPM of desired.
  3. Command the engine speed up and down with a scan tool. Increase the engine speed in 25 RPM increments while comparing the desired engine speed to the actual engine speed, the actual engine speed should stay within 25 RPM of the desired engine speed.
  4. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Inspect for any condition that can reduce idle speed by increasing engine load.
    2. • Incorrect torque converter clutch (TCC) operation
    • Accessories that require additional torque to operate
    • Excessive deposits in the throttle body--Refer to Throttle Body Inspection and Cleaning .
    • Restricted exhaust--Refer to Restricted Exhaust .
    • Mechanical conditions that limit engine speed
  2. Inspect for any condition that can increase idle speed.
    3. • Vacuum leaks
    • Unmetered air entering the engine, after the mass air flow
    • A faulty positive crankcase ventilation (PCV) valve

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.