For 1990-2009 cars

### 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.

### Conditions for Running the DTC

• | One or more of the following DTCs are not set: P0110, P0115, P0116, P0411, P0440, P0442, P0443, P0446, P0455, P0500, P1120, P1220.

• | The intake air temperature (IAT) is more than 0°C (32°F).

• | The engine coolant temperature (ECT) is more than 80°C (176°F).

• | The engine load is less than 2 percent.

• | The evaporative emissions (EVAP) diagnostic is not running.

• | The EVAP is not purging.

• | Vehicle speed is 0 km/h (0 mph)

• | Secondary air diagnostic is not running.

### Conditions for Setting the DTC

The actual engine RPM is lower than the desired idle speed by at least 100 RPM.

### Action Taken When the DTC Sets

The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.

• | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

For an intermittent, refer to Symptoms .

### 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 or not the engine can achieve the commanded RPM, and if not, whether the RPM is too high or too low.

#### DTC P0506 - Idle Speed Low

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any TAC, TP, or APP DTCs set? | -- | Go to the applicable DTC table | Go to Step 3
3 |

1. Start the engine.
2. Command the engine speed up to 1400 RPM, down to 600 RPM, up to 1400 RPM, and then exit using the scan tool

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

--

Go to Diagnostic Aids

Go to Step 4

4 | Is the engine RPM greater than 100 RPM above the desired RPM? | -- | Go to Step 5 | Go to Step 6
5 | Check for the following conditions:

• | Vacuum leaks

• | Throttle blade not closing properly

• | A faulty crankcase ventilation system

Is the action complete?

--

Go to Step 7

--

6 | Check for the following conditions:

• | Excessive deposits in the throttle body.

• | A parasitic load on the engine, for example: a transmission problem, a belt driven accessory problem, etc.

Is the action complete?

--

Go to Step 7

--

7 |

1. Using the scan tool, clear the DTCs.
2. Start the engine.
3. Allow the engine to idle until the engine reaches the normal operating temperature.
4. Select DTC and the Specific DTC function.
5. Enter the DTC number that was set.
6. Operate the engine within the Conditions for Running this DTC until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

Go to Step 8

Go to Step 2

8 | Does the scan tool display any additional, undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK