DTC P0506 or P0507. Chevrolet Epica 2005

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC P0506 or P0507

Circuit Description

The engine control module (ECM) controls the engine idle speed by adjusting the position of the idle air control (IAC) valve pintle. The IAC valve is a stepper motor driven by two internal coils. The movement of the IAC valve is controlled electrically by four circuits. Drivers within the ECM control the polarity of the two windings inside the IAC valve through these circuits. The ECM, by commanding the correct polarity in sequence, is able to command the motor within the IAC valve to rotate clockwise or counter clockwise in steps. In order for the armature of the stepper motor of the IAC valve to turn one revolution, it needs to move approximately twenty four steps. The IAC valve motor is linked by a gear drive to the IAC valve pintle. The electrical pulses sent to the IAC valve coils, by the ECM, allows the pintle to extend or retract into the passage in the throttle body. By retracting the pintle, air is allowed to bypass the throttle valve, which will increase air flow and raise engine speed. When the pintle is extended, bypass air is decreased which lowers engine speed. IAC valve movement is measured in counts on the scan tool. Each count is equivalent to a step of the IAC valve. When the IAC valve is fully extended, and seated in the throttle body bore, the scan tool displays zero and the engine speed is slow. As the IAC valve pintle retracts the counts will raise along with engine speed.

If the ECM detects that the engine speed is not within a predetermined amount of the desired engine speed, a diagnostic trouble code (DTC) sets.

IAC Valve Reset

When the ignition switch is turned OFF for more than ten seconds an IAC valve reset occurs. At that time, the ECM commands the IAC valve to extend for a certain period which allows the IAC pintle to seat in the throttle body bore. This position is then sensed as zero count position for the IAC valve by the ECM. It must be observed that the IAC valve position is only sensed by the ECM measuring counts or steps of the driver circuit, there is no direct sensing of its exact position. When this extend time period ends, the ECM then commands the IAC valve to retract a predetermined amount. This will allow for a high engine speed on the next ignition cycle. If for any reason the IAC valve pintle moves after this reset, before the next ignition cycle, the ECM will not be able to detect it and will affect the ability to control engine idle. When the IAC valve is removed for any reason the reset must be performed. Refer to Idle Learn .

DTC Descriptor

This diagnostic procedure supports the following DTCs:

•	DTC P0506 Idle Speed Low

•	DTC P0507 Idle Speed High

Conditions For Running the DTC

•	DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0141, P0171, P0172, P0201 - P0204, P0300, P0336, P0337, P0341, P0342, P0351, P0352, P0402, P0404, P0405, P0406, P0443, P0502, P1134, P1167, P1171, and P1404 are not set.

•	The engine coolant temperature (ECT) is more than 60°C (140°F).

•	The intake air temperature is more than -20°C (-4°F)

•	The barometric pressure (BARO) is more than 72 kPa.

•	The engine run time is more than 60 seconds.

•	The manifold absolute pressure (MAP) is less than 60 kPa -- P0506 only.

•	The manifold absolute pressure (MAP) is more than 22 kPa -- P0507 only.

•	The ignition voltage is between 11.0 and 16.0 volts.

•	This DTC runs continuously when the above conditions are met for 5 seconds.

Conditions for Setting the DTC

DTC P0506

•	The actual engine speed is 100 RPM less than the desired engine speed.

•	The condition exists for 10 seconds.

DTC P0507

•	The actual engine speed is 200 RPM more than the desired engine speed.

•	The condition exists for 10 seconds.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) on the third 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 4 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.

Diagnostic Aids

•	A low, high or unstable idle condition may be caused by a non-IAC system condition that cannot be overcome by the IAC valve. Refer to Rough, Unstable, or Incorrect Idle and Stalling .

•	If the condition is intermittent, refer to Intermittent Conditions .

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

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

Did you perform the Diagnostic System Check - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Important: Ensure that engine speed stabilizes with each commanded RPM change in order to determine if engine speed stays within the specified value of the commanded RPM.

Start the engine.
Turn OFF all the accessories.
Command the engine speed to 1800 RPM, then to 600 RPM, and then to 1800 RPM with a scan tool.
Exit the RPM control function.

Is the engine speed within the specified value of each command of the RPM?

100 RPM

Go to Step 3

Go to Step 4

Observe the Freeze Frame and the Failure records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
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 data.

Does the DTC fail this ignition cycle?

Go to Step 4

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the IAC valve.
Connect the J 37027-A Idle Air Control Motor Tester to the IAC valve.
Start the engine.
Command the IAC valve in until near 600 RPM is reached with the IAC motor driver, then command the IAC valve out until near 1,800 RPM is reached.
Return the engine speed to the desired idle, as displayed on the scan tool.

Did the engine speed steadily decrease to near 600 RPM and steadily increase to near 1,800 RPM when the IAC valve was commanded in and out?

Go to Step 6

Go to Step 5

Is the engine speed over 100 RPM less than the desired engine speed?

Go to Step 11

Go to Step 12

Turn OFF the ignition.
Connect a test lamp between one of the IAC valve control circuits and a good ground.
Start the engine.
With the J 37027-A , command low RPM while observing a scan tool until the IAC Counts start to increment.
With the J 37027-A , command high RPM while observing a scan tool until the IAC Counts start to increment.
While the IAC Counts are incrementing, observe the test lamp.
Return the engine idle speed to the desired idle, as displayed on the scan tool.
Repeat the above procedure for the other 3 IAC valve control circuits.

Important: If the test lamp illuminates dimly on one or more of the IAC circuits, repair the high resistance in the appropriate IAC circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did the test lamp remain ON and never flash while the IAC Counts were incrementing at any of the IAC valve control circuits?

Go to Step 10

Go to Step 7

Did the test lamp remain OFF and never flash while the IAC Counts were incrementing at any of the IAC valve circuits during the above test?

Go to Step 9

Go to Step 8

Connect a test lamp between the IAC coil A low circuit and the IAC coil A high circuit at the IAC valve electrical connector.
With the J 37027-A , command low RPM while observing a scan tool until the IAC counts start to increment.
With the J 37027-A , command high RPM while observing a scan tool until the IAC Counts start to increment.
While the IAC counts are incrementing, observe the test lamp.
Return engine idle speed to the desired idle, as displayed on the scan tool.
Repeat the above procedure with the test lamp connected between the IAC coil B low circuit and the IAC coil B high circuit at the IAC valve electrical connector.
Return the engine speed to the desired idle, as displayed on the scan tool.

Did the test lamp stay illuminated and never flash while the IAC counts were incrementing during the above test?

Go to Diagnostic Aids

Go to Step 16

Turn OFF the ignition.
Disconnect the ECM. Refer to Engine Control Module Replacement .
Test the IAC valve circuits for an open or for a short to ground on the IAC valve circuit that the test lamp remained OFF. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

Turn ON the ignition.
Test the IAC valve circuits for a short to voltage on the IAC valve circuit where the test lamp remained illuminated. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

Remove the IAC valve. Refer to Idle Air Control Valve Replacement .
Inspect for the following conditions:

•	The throttle body for damage and/or tampering

•	For a clogged IAC passage

•	For excessive deposits on the throttle plate

•	For excessive deposits in the throttle bore

•	For excessive deposits on IAC valve pintle

•	For a restricted air intake system

Did you find and correct the condition?

Go to Step 17

Go to Step 13

Remove the IAC valve. Refer to Idle Air Control Valve Replacement .
Inspect for the following conditions:

•	The throttle body for damage and/or tampering

•	For vacuum leaks

•	For an incorrectly installed PCV valve and hose

•	For a malfunctioning PCV valve

•	The throttle shaft for binding

•	The throttle linkage for binding

Did you find and correct the condition?

Go to Step 17

Go to Step 13

Test for an intermittent and for a poor connection at the IAC Valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 15

Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 16

Important: If the IAC valve is removed or replaced, perform the Idle Learn .

Replace the IAC valve. Refer to Idle Air Control Valve Replacement .

Did you complete the replacement?

Go to Step 17

Important: If the ECM power is removed or the ECM is replaced, perform the Idle Learn .

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 17

Clear the DTCs with a scan tool.
Turn the ignition OFF for 30 seconds.
Start the engine.
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.

Does the DTC fail this ignition?

Go to Step 2

Go to Step 18

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK