GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P0506

Circuit Description

The electronic throttle control (ETC) system uses various inputs from the powertrain control module (PCM) to control idle speed through serial data circuits to the throttle actuator control (TAC) module. The DC motor located on the throttle body actuates the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the TAC module commands the throttle plate open allowing more air to bypass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this diagnostic trouble code (DTC) will set.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0171, P0172, P0174, P0175, P0200, P0300, P0440, P0442, P0443, P0500, P0502, P0503, P1120, P1220, P1221, or P1441 are not set.
    • The engine is running for greater than 60 seconds.
    • The engine coolant temperature (ECT) is greater than 60°C (140°F).
    • The intake air temperature (IAT) is greater than -10°C (14°F).
    • The barometric pressure (BARO) is greater than 65 kPa.
    • The system voltage is between 9-18 volts.
    • The vehicle speed is less than 1.7 km/h (1 mph).
    • The accelerator pedal position (APP) indicated angle is 0 percent.

Conditions for Setting the DTC
    • The actual idle speed is 100 RPM less than the desired idle speed.
    • All of the above conditions are present for 5 seconds.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This test determines whether the engine can achieve the commanded RPM.

DTC P0506 Idle Control System Low RPM

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Set the parking brake and block the drive wheels.
  2. Start the engine.
  3. Turn OFF all of the accessories.
  4. Use the scan tool RPM control function in order to command the engine RPM to 1,500 RPM and then to 500 RPM and back to 1,500 RPM.
  5. Exit the RPM control function.

Did the engine speed stay within 100 RPM of the commanded RPM during the above test?

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC reset?

Go to Step 4

Go to Intermittent Conditions

4

Inspect for the following conditions:

    • Excessive deposits in the throttle body.
    • Objects blocking the air intake system.
    • Parasitic load on the engine (i.e., transmission problems, etc.).

Did you complete the repair?

Go to Step 5

--

5
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 6

Go to Step 2

6

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK