GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 CTS 🢒 DTC 🢒 DTC P0506

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 air flow into the engine. In order to increase idle speed the TAC system opens the throttle plate allowing more air flow into the engine. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this code sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0506 Idle Speed Low

Conditions for Running the DTC
    • DTCs P0068, P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0171, P0172, P0200, P0300, P0336, P0445, P0442, P0446, P0452, P0453, P0502, P0503, P0120, P0220, P2101, P1516, P2135, P0641, or P0651 are not set.
    • The engine is operating for more than 60 seconds.
    • The engine coolant temperature (ECT) is more than 60°C (140°F).
    • The intake air temperature (IAT) is more than -10°C (14°F).
    • The barometric pressure (BARO) is more 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) sensor is at 0 percent.
    • DTC P0506 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The PCM detects the actual idle speed is 100 RPM lower than the desired idle speed for 5 continuous 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 RPMs, the test determines whether the RPM is too high or too low.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views and Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Start the engine.
  2. Ensure the engine is at operating temperature.
  3. Command the engine speed to 1,500 RPM, then to 500 RPM, and back to 1,500 RPM with a scan tool.
  4. Exit the RPM control function.

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

Go to Intermittent Conditions

Go to Step 3

3

Inspect for any condition that can reduce idle speed by increasing engine load. The following examples are possible conditions:

    • Incorrect torque converter clutch (TCC) operation
    • Accessories that require additional torque to operate
    • Restricted exhaust
    • Mechanical conditions that limit engine speed

Did you complete the action?

Go to Step 4

--

4
  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. 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 5

5

Important: Be aware that repairing 1 individual condition may correct more than 1 DTC.

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK