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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0506

Circuit Description

The throttle actuator control (TAC) motor is controlled by the engine control module (ECM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the ECM commands the throttle closed, which reduces air flow into the engine. In order to increase idle speed, the ECM commands the throttle plate open, which allows more air flow into the engine. If the actual idle RPM does not match the desired idle RPM within a calibrated time, DTC P0506 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0506 Idle Speed Low

Conditions for Running the DTC
    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0122, P0123, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0270, P0271, P0273, P0274, P0276, P0277, P0279, P0280, P0282, P0283, P0351, P0352, P0353, P0354, P0355, P0356, P0357, P0358, P0638, P1106, P1107, P2100, P2101, P2108, P2119, P2122, P2123, P2127, P2128, P2135, P2138, or P2176 are not set.
    • The engine is operating.
    • The engine coolant temperature (ECT) is more than -7°C (+19°F).
    • The ECT is less than 120°C (248°F).
    • The vehicle speed is 0 km/h (0 mph).
    • DTC P0506 runs continuously once the above conditions are met.

Conditions for Setting the DTC
    • The actual idle speed is 100 RPM lower than the desired idle speed.
    • The above condition is present for more than 10 seconds.

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 number below refers to the step number on the diagnostic table.

  1. This test determines whether the engine can achieve the commanded RPM.

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 - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

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

Does the actual engine speed correspond to the desired engine speed, 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. Examples include:

    • 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

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