GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The idle speed is controlled by the engine control module (ECM). The ECM will command the throttle valve motor to open or close the throttle valve in order to maintain the desired idle speed. If an RPM out of range condition exists, this DTC will set.

Conditions for Running the DTC

    • DTCs P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0221, P0222, P0223, P0440, P0442, P0443, P0444, P0445, P0446, P0447, P0448, P0449, P0451, P0452, P0453, P0500 are not set.
    • The intake air temperature (IAT) is more than 0°C (32°F).
    • The engine coolant temperature (ECT) is more than 60°C (140°F).
    • The engine load is less than 40 percent.
    • The evaporative emissions (EVAP) diagnostic is not running.
    • The EVAP is not purging.
    • The vehicle speed is 0 km/h (0 mph).

Conditions for Setting the DTC

The control module detects that the actual engine RPM is less than the desired idle speed by at least 100 RPM.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • 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 emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. If any of the listed DTCs are present, correct the condition before returning to this table.

  2. This test determines whether the engine can achieve the commanded RPM, and if not, whether the RPM is too high or too low.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Is DTC P1551, P2100, P2101, P2105, P2107, P2119, or P2176 also set?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Start the engine.
  2. Command the engine speed up to 1,400 RPM, down to 600 RPM, up to 1,400 RPM, then exit using the scan tool.

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

Go to Intermittent Conditions

Go to Step 4

4

Inspect for the following conditions:

    • Excess deposits in the throttle body
    • A parasitic load on the engine, for example: a transmission condition, a belt driven accessory condition, etc.

Did you find and correct the condition?

Go to Step 5

--

5

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 6

6

Observe the Capture Info with a scan tool.

Are there any DTCs that have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK