DTC P0506 Idle Speed Low. Oldsmobile Intrigue 1999

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1999 🢒 Intrigue 🢒 DTC 🢒 DTC P0506 Idle Speed Low

Engine Controls Components
Fuel Control
OBD II Symbol Description Notice

Circuit Description

The powertrain control module (PCM) controls the engine idle speed by adjusting the position of the idle air control (IAC) motor pintle. The IAC is a bi-directional motor driven by 2 coils. The PCM sends pulses (steps) to the IAC in order to extend or retract the IAC pintle into a passage in the throttle body to decrease or increase air flow. The commanded IAC position (displayed in counts) may be monitored on a scan tool. A higher number of counts indicates more commanded airflow (pintle retracted). This method allows highly accurate control of idle speed and quick response to changes in the engine load. If the PCM detects a condition where a too low idle speed is present and the PCM is unable to adjust idle speed by increasing the IAC counts, DTC P0506 is set indicating a problem with the idle control system.

Conditions for Running the DTC

•	None of the following DTCs are set:

-	Throttle position (TP) sensor DTCs

-	Vehicle speed sensor (VSS) DTCs

-	Evaporative emissions (EVAP) system DTCs

-	Intake air temperature (IAT) sensor DTCs

-	Manifold absolute pressure (MAP) sensor DTCs

-	Exhaust gas recirculation (EGR) pintle position DTCs

-	Engine coolant temperature (ECT) sensor DTCs

-	Crankshaft position (CKP) sensor DTCs

-	Mass air flow (MAF) sensor DTCs

-	Misfire DTCs

-	Fuel trim DTCs

-	Fuel injector DTCs

•	The BARO is greater than 65 kPa.

•	The engine is running for at least 60 seconds.

•	The system voltage is between 9 and 16 volts.

•	The ECT is more than 70°C (158°F).

•	The vehicle speed is less than 3 MPH.

•	The IAT is more than -18°C (0°F).

•	The throttle is closed.

Conditions for Setting the DTC

•	The engine speed is over 100 RPM lower than the Desired Idle.

•	The above condition is present for longer than 15 seconds.

Action Taken When the DTC Sets

•	The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed.

•	The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC

•	The PCM turns the MIL off during the third consecutive trip in which the diagnostic has run and passed.

•	The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.

•	The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids

Inspect for the following conditions:

•	A faulty connection at the PCM or the IAC motor. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections.

•	A damaged harness. Inspect the wiring harness for damage.

•	A restricted air intake system. Inspect for a possible collapsed air intake duct, restricted air filter element, or foreign objects blocking the air intake system.

•	The throttle body. Inspect for objects blocking the IAC passage or the throttle bore, excessive deposits in the IAC passage and the IAC pintle, and excessive deposits in the throttle bore and on the throttle plate.

•	A large vacuum leak. Inspect for a condition that causes a large vacuum leak, such as a incorrectly installed or malfunctioning crankcase ventilation valve or brake booster hose disconnected.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table.

This vehicle is equipped with a powertrain control module (PCM) which utilizes an electrically erasable programmable read-only memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

DTC P0506 - Idle Air Control System RPM Low

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Are any other DTC(s) set?

Diagnose the other DTC first.

Go to Step 3

Start the engine.
Turn off all accessories (A/C, Rear defroster etc.).
Use a scan tool in order to command the engine RPM up to 1500, down to 650, and then up to 1500 while monitoring the Engine Speed.

Does Engine Speed remain within the specified value of Desired Idle for each RPM command?

± 100 RPM

Refer to Diagnostic Aids

Go to Step 4

Disconnect the IAC.
Install a J 37027-A IAC System Monitor.
With the engine running, command the RPM up to 1500, down to 650, and then up to 1500 while observing the IAC System Monitor node lights.

Does each node light cycle red and green (never OFF)?

Go to Step 6

Go to Step 5

Test the following circuits for an open, short to voltage, or short to ground:

•	The IAC A Low.

•	The IAC A High.

•	The IAC B Low.

•	The IAC B High.

If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

Go to Step 11

Go to Step 9

Visually/physically inspect for the following conditions:

•	Any throttle body tampering (throttle lever stop screw turned).

•	Inspect for a collapsed air intake duct, restricted air filter element, or foreign objects blocking the air intake system.

•	Remove the IAC valve. Refer to Idle Air Control Valve Replacement .

•	Inspect for objects blocking the IAC passage or the throttle bore, excessive deposits in the IAC passage and on the IAC pintle, and excessive deposits in the throttle bore and on the throttle plate. Refer to Throttle Body Assembly Replacement .

If a problem is found, repair as necessary.

Was a problem found?

Go to Step 11

Go to Step 7

Inspect for a faulty connection at the IAC harness connector.
If a problem is found, replace the loose terminals as necessary. Refer to Connector Repairs in Wiring Systems.

Was a problem found?

Go to Step 11

Go to Step 8

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

Did you complete the repair?

Go to Step 11

Inspect for a faulty connection at the PCM harness connector.
If a problem is found, replace the loose terminals as necessary. Refer to Connector Repairs in Wiring Systems.

Was a problem found?

Go to Step 11

Go to Step 10

Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Did you complete the repair?

Go to Step 11

Start the engine.
Turn all accessories off (A/C, Rear defroster etc.).
Use the scan tool in order to command the RPM up to 1500, down to 650, and then up to 1500 while monitoring the Engine Speed.

Does the Engine Speed remain within the specified value of Desired Idle for each RPM command?

± 100 RPM

System OK

Go to Step 2