For 1990-2009 cars

### Circuit Description

The Throttle Actuator Motor is controlled by the TAC Module using various inputs from the PCM which are communicated across serial data. The DC motor located on the throttle body drives 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 DTC sets.

### Conditions for Running the DTC

• | No Misfire, EGR, TP, VSS, ECT, MAP, IAT, Fuel Trim, Fuel Injector, CKP or MAF DTCs set.

• | Engine is operating for at least 2 minutes.

• | ECT is greater than -40°C (-40°F)

• | IAT is greater than -40°C (-40°F)

• | BARO is greater than 65 kPa

• | System voltage is between 9.0 and 18.0 volts

• | Vehicle speed is less than 3 mph

• | APP indicated Angle is less than 0.25%

### Conditions for Setting the DTC

• | The Actual idle speed is approximately 150 RPM lower than the Desired idle speed.

• | All above conditions 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 and Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been 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 the scan tool.

### Diagnostic Aids

Important: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing/replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

Using Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent, refer to Symptoms .

### Test Description

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

1. 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 Control System Low RPM

Step | Action | Value(s) | 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 |

1. Start the engine.
2. With a scan tool, command the engine speed up to 1500 RPM, down to 500 RPM, up to 1500 RPM.
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 more than 100 RPM above or below the Desired RPM? | -- | Go to Step 4 | Go to Step 5
4 | Inspect for the following conditions:

• | Excessive deposits in the throttle body.

• | A faulty PCV valve.

Did you complete the repair?

--

Go to Step 6

--

5 | Inspect for the following conditions:

• | Excessive deposits in the throttle body.

• | Parasitic load on the engine (i.e. transmission problem etc.).

Did you complete the repair?

--

Go to Step 6

--

6 |

1. Use the scan tool in order to record Fail Records and clear the DTCs.
2. Operate the Fail Record conditions.

Does the DTC reset?

--

Go to Step 2

Go to Step 7

7 | Does the scan tool indicated any DTCs set that you have not diagnosed? | -- | Go to the applicable DTC table | System OK