GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P0506 or P0507

Circuit Description

The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle plate. In order to decrease idle speed the TAC system closes the throttle plate reducing airflow into the engine. In order to increase idle speed the TAC system opens the throttle plate allowing more airflow into the engine. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

Conditions for Running the DTC
    • DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0200, P0336, P0401, P1120, P1220, P1221, P1514, P1515, P1516, P1635, or P1639 are not set.
    • The engine is operating for at least 2 seconds.
    • The engine coolant temperature (ECT) is more than -40°C (-40°F).
    • The intake air temperature (IAT) is more than -40°C (-40°F).
    • The barometric pressure (BARO) is more than 65 kPa.
    • The system voltage is between 9-18 volts.
    • The vehicle speed is less than 4.8 km/h (3 mph).

Conditions for Setting the DTC
    • The actual idle speed is approximately 150 RPM lower than or 100 RPM greater than the desired idle speed.
    • All above conditions are present for 15 seconds.

Action Taken When the DTC Sets
    • The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
    • The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC
    • The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using a scan tool.

Diagnostic Aids

If the condition is intermittent, refer to Intermittent Conditions .

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. If the engine does not reach the commanded RPM, the test determines whether the RPM is too high or too low.

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. Start the engine.
  2. Command the engine speed up to 1,500 RPM, down to 500 RPM, and up to 1,500 RPM with a scan tool.
  3. Exit the RPM control function.

Does the engine speed correspond, within 100 RPM, with each command?

Go to Diagnostic Aids

Go to Step 3

3

Is the engine RPM 100 RPM more than the desired RPM?

Go to Step 4

Go to Step 5

4

Inspect for the following conditions:

    • Vacuum leaks
    • Excessive deposits in the throttle body
    • A faulty positive crankcase ventilation (PCV) valve

Did you complete the repair?

Go to Step 6

--

5

Inspect for energy draining load on the engine, such as ones caused by transmission conditions.

Did you find and correct the condition?

Go to Step 6

--

6
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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 7

Go to Step 2

7

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