DTC P0506 Idle Speed Low. Chevrolet Impala 2000

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2000 🢒 Impala 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P0506 Idle Speed Low

Engine Controls Component Views
Engine Data Sensors-MAF, EVAP Vent, EVAP Purge, EGR
Handling ESD Sensitive Parts Notice
OBD II Symbol Description 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 applies current to the IAC coils in pulses (counts) to extend the IAC pintle into a passage in the throttle body to decrease air flow. The PCM reverses the current to retract the pintle, increasing air flow. 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.

Conditions for Running the DTC

•	No active TP, ECT, MAP, IAT, MAF, CKP, sensor, EVAP, misfire, EGR, VSS, Fuel Trim, injector circuit, DTCs active.

•	Engine coolant temperature is above 70°C (158°F).

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

•	System voltage is between 9.0-16.0 volts.

•	The vehicle speed is less than 3 mph.

•	Intake air temperature is above -18°C (0°F).

•	The throttle is closed

•	BARO is above 65 kPa.

Conditions for Setting the DTC

•	Engine speed is more than 100 RPM lower than Desired Idle.

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

Action Taken When the DTC Sets

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

•	The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

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 valve -- Inspect harness connectors for the following conditions:

-	Backed out terminals

-	Improper mating

-	Broken locks

-	Improperly formed or damaged terminals

-	Poor terminal to wire connection

-	Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

•	Damaged harness -- Inspect the wiring harness for damage. Refer to Wiring Repairs .

•	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, on the IAC pintle, in the throttle bore and on the throttle plate.

•	Large vacuum leak -- Check for a condition that causes a large vacuum leak, such as an incorrectly installed or faulty PCV valve or the brake booster hose disconnected. Refer to Crankcase Ventilation System Inspection and Emission Hose Routing Diagram .

If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number below refers to the step number 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 being replaced, the new PCM must be programmed.

Step

Action

Values

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 DTCs set?

Go to Diagnostic Trouble Code (DTC) List/Type

Go to Step 3

Start the engine.
Turn OFF all accessories.
Using a scan tool, command RPM up to 1500, down to 650, and then up to 1500 while monitoring engine speed on the scan tool.

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

50 RPM

Go to Diagnostic Aids.

Go to Step 4

Turn OFF the ignition.
Disconnect the IAC valve.
Install an J 37027-A IAC Node Lamp 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 lamp 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:

•

IAC A Low

•	IAC A High

•

IAC B Low

•	IAC B High

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

Did you find and correct the condition?

Go to Step 11

Go to Step 9

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

Did you find and correct the condition?

Go to Step 11

Go to Step 7

Visually and physically inspect for the following conditions:

•	Throttle body tampering, throttle lever stop screw turned.

•	Restricted air intake system -- 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.

Did any of the above require a repair?

Go to Step 11

Go to Step 8

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

Did you complete the replacement?

Go to Step 11

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

Did you find and correct the condition?

Go to Step 11

Go to Step 10

Important: : Replacement PCM must be programmed.

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

Did you complete the replacement?

Go to Step 11

Reinstall and connect components as necessary.
Start the engine.
Turn OFF all of the accessories.
Using a scan tool, command RPM up to 1500, down to 650, and then up to 1500 while monitoring engine speed on the scan tool.

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

50 RPM

System OK

Go to Step 2