GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 CTS 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0506, P0507, or P050A

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

DTC P050A: Cold Start Idle Air Control (IAC) System Performance

Circuit/System Description

The throttle actuator control (TAC) motor is a DC motor that is part of the throttle body assembly. The TAC motor drives the throttle valve. The engine control module (ECM) controls the TAC motor based on throttle position sensor input. The idle speed is controlled by the ECM based on various inputs. The ECM commands the TAC motor to open or close the throttle valve in order to maintain the desired idle speed. If the ECM detects the actual idle speed and the desired idle speed are not within a predetermined amount, this DTC sets.

Conditions for Running the DTC

P0506 and P0507

    •  Before the ECM can report DTC P0506 or P0507 failed, transmission DTCs P0722 and P0723 must run and pass.
    • DTCs P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0442, P0443, P0446, P0455, P0458, P0459, P0496, P0722, and P0723 are not set.
    • The volumetric efficiency is less than 35 percent, DTC P0506 only.
    • The vehicle speed is 0 km/h (0 mph).
    • The evaporative emission (EVAP) canister purge valve is OFF.
    • The intake air temperature (IAT) is more than -10.5°C (+13°F).
    • The engine coolant temperature (ECT) is greater than -10.5°C (+13°F).
    • A vehicle speed was detected prior to the diagnostic running.
    • DTC P0506 and P0507 run continuously once the above conditions are met for more than 10 seconds.

P050A

    • DTCs P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0442, P0443, P0446, P0455, P0458, P0459, P0496, P0722, and P0723 are not set.
    • The volumetric efficiency is less than 35 percent.
    • The ECT is -10 to +40°C (+14 to +104°F) at cold start.
    • The engine is operating for more than 7 seconds.
    • DTC P050A runs once an ignition cycle when the conditions above have been met for 5 seconds.

Conditions for Setting the DTC

P0506

The actual engine speed is less than the desired idle speed by at least 100 RPM for 4 seconds.

P0507

    • The actual engine speed is more than the desired idle speed by at least 200 RPM for 4 seconds.
        OR
    • The ECM detects 3 fuel cut-offs due to an engine over speed condition while the engine is idling.

P050A

The actual engine speed is more or less than the desired idle speed by at least 100 RPM for 4 seconds during a cold start.

Action Taken When the DTC Sets

DTCs P0506, P0507, and P050A are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0506, P0507, and P050A are Type B DTCs.

Diagnostic Aids
    • Inspect for a condition in which the throttle valve may have been held open. For example, ice may have formed in the throttle bore.
    • For an intermittent condition, refer to Intermittent Conditions .
    • Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness connector terminals.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

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

DTC Type Reference

    •  Diagnostic Trouble Code (DTC) Type Definitions
    •  Diagnostic Trouble Code (DTC) Types

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification
  1. Observe the DTC information with a scan tool.
    2. ⇒If there are any throttle actuator control (TAC), throttle position (TP) sensor, or accelerator pedal position (APP) sensor DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Operate the engine within the conditions for running the DTCs for 1 minute. DTC P0506, P0507, or P050A should not set.

Circuit/System Testing

Engine operating, command the engine speed up to 1,400 RPM, down to 600 RPM, up to 1,400 RPM, and then exit using the scan tool. The engine speed should steadily increase and decrease as commanded.

⇒If the idle does not increase or decrease steadily, verify that one of the following conditions is not present:
    • Vacuum leaks
    • The throttle valve for the correct operation--A throttle valve that does not close correctly sets this DTC.
    • Restricted air intake system
    • The throttle body for damage and/or tampering
    • Incorrect or malfunctioning PCV valve
    • Excess deposits in the throttle body
    • A parasitic load on the engine--For example, a transmission condition, a belt driven accessory condition
       ⇒Repair the condition as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.