| Table 1: | IAC Valve Terminal (Pin) Location |
Circuit Description
The DTC P0506 Idle Speed Low diagnostic monitors the engine speed. The powertrain control module (PCM) controls the idle air control (IAC) valve in order to regulate the air flow through the idle air bypass passage. The amount of air flowing through the idle air bypass passage determines the idle speed. The PCM directs the IAC valve according to changes in the engine load. A stalling or poor idle concern may be caused by the IAC valve not operating properly.
Conditions for Running the DTC
| • | DTC P0500 is not set. |
| • | Barometric pressure (BARO) is more than 75 kPa. |
| • | Intake air temperature (IAT) is between -14° and +70°C (7-158°F). |
| • | Engine coolant temperature (ECT) is more than 70°C (158°F). |
| • | Engine is running in Closed Loop at idle. |
| • | No vehicle speed is detected |
| • | The throttle valve is closed |
| • | A/C is OFF |
| • | The power steering pressure (PSP) switch is OFF. |
Conditions for Setting the DTC
| • | The actual engine speed is 100 RPM less than the desired engine speed value with the IAC Motor Command near 100 percent. |
| • | The above condition exists for more than 30 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool Clear DTC Information function. |
Diagnostic Aids
The IAC Motor Command parameter of the scan tool will appear fixed when a Current or Pending DTC P0506 is set. Clear the DTC in order to observe present time IAC Motor Command readings.
Any malfunction that can cause a low idle condition can cause a DTC P0506 to set.
An intermittent malfunction may be caused by a fault in the idle air control (IAC) system electrical circuits. Check the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .
Use the following table in order to locate the correct terminals to test during diagnosis. The table layout corresponds to the pin location of the IAC valve electrical terminals.
Lock Tab | ||
3 | 2 | 1 |
6 | 5 | 4 |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step prompts the technician to check for any condition that can affect the ability of the IAC valve to control engine idle speed. A DTC P0506 can set even if there is no fault in the IAC system. Any condition that can affect the idle speed of the engine must be repaired first, in order to enable proper diagnosis of the DTC P0506.
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This step tests whether the PCM can operate the IAC valve with the scan tool. The IAC valve can be commanded to increase and/or decrease engine speed by using the scan tool RPM Control function.
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This step checks whether the malfunction that caused the DTC P0506 is still present. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0506 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0506 appears in the Not Ran Since Code Cleared list, the DTC P0506 diagnostic has not yet run. When the DTC P0506 does not appear in the Not Ran Since Code Cleared list, the DTC P0506 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0506 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.
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This step determines whether the PCM is attempting to control the IAC valve. Each IAC coil control circuit should indicate a high voltage of 12 volts or more and then a low voltage of 0.0-1.0 volts as the PCM commands changes in the engine speed. Remember to perform this test at normal engine operating temperatures and clear all DTCs before attempting RPM control with the scan tool.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0506 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0506 appears in the Not Ran Since Code Cleared list, the DTC P0506 diagnostic has not yet run. When the DTC P0506 does not appear in the Not Ran Since Code Cleared list, the DTC P0506 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0506 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||||||
Did you find and correct a condition? | -- | Go to Step 4 | Go to Step 3 | |||||||||
Does the engine speed increase and decrease as commanded by the scan tool? | -- | Go to Step 4 | Go to Step 6 | |||||||||
Is DTC P0506 set? | -- | Go to Step 6 | Go to Step 5 | |||||||||
5 |
Are the Engine Speed and the IAC Motor Command parameters within the specified ranges? | 700-800 RPM in P/N 10%-50% IAC Motor Command | System OK | |||||||||
6 |
Are the resistances within the specified range? | 21-23 ohms at 20°C (68°F) | Go to Step 7 | Go to Step 10 | ||||||||
Does the voltage of each IAC coil control circuit switch from high to low with the increase and decrease in the engine speed? | -- | Go to Step 9 | Go to Step 8 | |||||||||
8 |
Did you find and correct a condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||||||
10 | Replace the IAC valve. Refer to Idle Air Control Valve Replacement . Is the action complete? | -- | Go to Step 12 | -- | ||||||||
11 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 12 | -- | ||||||||
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 | |||||||||
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||
