DTC P0507 Idle Speed High. Buick Century 1999

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1999 🢒 Century 🢒 DTC 🢒 DTC P0507 Idle Speed High

Engine Controls Components
Cell 20: Engine Oil Level, Engine Oil Pressure and IAC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM controls the air entering into the engine with an Idle Control (IAC) valve. In order to increase the idle rpm, the PCM commands the pintle inside the IAC valve away from the throttle body seat. This allows more air to bypass through the throttle blade. In order to decrease the rpm the PCM commands the pintle towards the throttle body seat. This reduces the amount of air bypassing the throttle blade. A scan tool will read the IAC valve pintle position in counts. The higher the counts, the more air that is allowed to bypass the throttle blade.

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.

•	Vehicle Speed is less than 3 mph.

•	Intake Air Temperature is above -18°C (0°F).

•	The throttle is closed

•	BARO above 65 kPa.

•	Engine run time is greater than 2 minutes.

Conditions for Setting the DTC

•	The IAC valve reads less than 15 counts on the scan tool.

•	Engine Speed is more than 100 RPM higher than Desired Idle.

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:

Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

•	Poor terminal connection.

Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems.

•	Damaged harness.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems.

•	Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

Number(s) below refer to the step number(s) 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

Value(s)

Yes

Was the Powertrain OBD System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Are any other DTCs set?

Go to other DTC first

Go to Step 3

Start the engine.
Turn all accessories off (A/C, Rear defroster etc.).
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 remain within the specified value of Desired Idle for each RPM command?

±50 RPM

Go to Diagnostic Aids

Go to Step 4

Disconnect the IAC.
Install J 37027-A IAC System Motor Analyzer.
With the engine running, command RPM up to 1500, down to 650, and then up to 1500 while observing the l J 37027-A IAC System Motor Analyzer or equivalent.

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

Go to Step 6

Go to Step 5

Check 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 .

Was a problem found?

Go to Step 11

Go to Step 9

Visually/physically inspect for the following conditions:

•	Vacuum leaks.

•	Throttle body tampering (Throttle Lever Stop Screw turned).

•	Throttle Plate or Throttle Shaft for binding.

•	Accelerator and Cruise Control cables for being misadjusted or for binding.

•	Faulty, missing, or incorrectly installed Positive Crankcase Ventilation valve.

Does any of the above require a repair?

Go to appropriate section for on-vehicle service

Go to Step 7

Check for a poor connection at the IAC harness connector.
If a problem is found, replace faulty terminals as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs .

Was a problem found?

Go to Step 11

Go to Step 8

Replace the IAC valve. Refer to IAC Valve Replacement .

Is the action complete?

Go to Step 11

Check for a poor connection at the PCM harness connector.
If a problem is found, replace faulty terminals as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals and Connector Repairs .

Was a problem found?

Go to Step 11

Go to Step 10

Replace the PCM.

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

Is the action complete?

Go to Step 11

Start the engine.
Turn all accessories off (A/C, Rear defroster etc.).
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 remain within the specified value of Desired Idle for each RPM command?

±50 RPM

System OK

Go to Step 2