DTC P0506 Idle Speed Low. Pontiac Bonneville 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Bonneville 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P0506 Idle Speed Low

Engine Controls Components
MAF, IAC, and Knock Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM controls engine idle speed by adjusting the position of the idle air control (IAC) motor pintle. The IAC is a bi-directional motor driven by two coils. The PCM sends pulses (steps) to the IAC 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) can be monitored on the 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 engine load. If the PCM detects a condition where too low of an idle speed is present and the PCM is unable to adjust idle speed by increasing the IAC counts, DTC P0506 will set indicating a problem with the idle control system.

Conditions for Running the DTC

•	None of the following DTCs are set:

-	Vehicle speed sensor (VSS)

-	Evaporative Emission (EVAP)

-	Throttle position (TP) sensor

Misfire

-	Intake air temperature (IAT) sensor

-	Manifold absolute pressure (MAP) sensor

Fuel trim

-	Fuel injector

-	Exhaust gas recirculation (EGR) system

-	Engine coolant temperature (ECT) sensor

-	Crankshaft position (CKP) sensor

-	Mass air flow (MAF) sensor

•	The vehicle speed is less than 3 mph.

•	The engine has been running for at least 2 minutes.

•	The system voltage is between 9 and 18 volts.

•	The BARO is more than 65 kPa (VIN K).

•	The BARO is more than 70 kPa (VIN 1).

•	The engine coolant temperature is more than -40°C (-40°F) (VIN K).

•	The engine coolant temperature is more than 70°C (158°F) (VIN 1).

•	The intake air temperature is more than -40°C (-40°F) (VIN K).

•	The intake air temperature is more than -18°C (-4°F) (VIN 1).

•	The throttle position is less than 0.25 percent (VIN K).

•	The throttle position is less than 1.31 percent (VIN 1).

Conditions for Setting the DTC

•	VIN K--The engine speed is more than 150 RPM less than the Desired Idle (negative idle speed error more than 150 RPM).

•	VIN 1--The engine speed is more than 175 RPM less than the Desired Idle (negative idle speed error more than 175 RPM).

•	Above conditions are present for more than 15 seconds.

Action Taken When the DTC Sets

•	The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure.

•	The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

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

Check for the following conditions:

•	Poor connection at PCM or IAC motor.

Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

•	Damaged harness.

Inspect the wiring harness for damage.

•	Restricted air intake system.

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

•	Throttle body.

Check for objects blocking the IAC passage or 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.

•	Large vacuum leak.

Check 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 numbers below refer the step numbers on the diagnostic table.

This vehicle is equipped with a 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

Values

Yes

Was the Powertrain On Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Are any other DTCs set?

Go to Diagnostic Trouble Code (DTC) List/Type

Go to Step 3

Start the engine.
Turn OFF all accessories (A/C, rear defroster etc.).
Using a scan tool, command the RPM up to 1500, down to 650, and then up to 1500 while monitoring the Engine Speed on the scan tool.

Does the engine speed vary less than the specified value from each RPM command?

100 RPM

Go to Diagnostic Aids

Go to Step 4

Disconnect the idle air control (IAC) valve.
Install an IAC node lamp J 37027-A or equivalent.
Start the engine, command RPM up to 1500, down to, and then up to 1500 while observing the node lamp.

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

Go to Step 6

Go to Step 5

Turn OFF the ignition switch.
Disconnect the PCM.
Turn ON the ignition switch.
Check the following circuits for an open, a short to voltage, or a 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

Check for a faulty connection at the IAC harness connector.
If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Was a problem found?

Go to Step 11

Go to Step 7

Visually/physically inspect for the following conditions:

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

•	Check for a possible 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 . Check for objects blocking the IAC passage or 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.

If a problem is found, repair as necessary.

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

Check for a faulty connection at the PCM harness connector.
If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems .

Was a problem found?

Go to Step 11

Go to Step 10

Important:: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Did you complete the repair?

Go to Step 11

Re-install the IAC valve and connect the components as necessary.
Start the engine.
Turn all accessories OFF (A/C, rear defroster etc.).
Using a scan tool, command the RPM up to 1500, down to 650, and then up to 1500 while monitoring the Engine Speed on the scan tool.

Does the engine speed vary less than the specified value from each RPM command?

100 RPM

System OK

Go to Step 2