DTC P0507 Idle Speed High. Buick Century 1996

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1996 🢒 Century 🢒 Engine 🢒 Engine Controls - 3.1L 🢒 DTC P0507 Idle Speed High

Engine Controls Components
Instrument Cluster, IAC, and Transmission Range Switch Systems
OBD II Symbol Description Notice
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 applies current to the IAC coils in steps (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 high of an idle speed is present and the PCM is unable to adjust idle speed by decreasing the IAC counts, DTC P0507 will set indicating a problem with the idle control system.

Conditions for Setting the DTC

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

•	Engine Coolant Temperature is above 70°C (122°F).

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

•	System voltage is between 9-16 volts.

•	Vehicle Speed is less than 3 MPH.

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

•	The throttle is closed

•	Engine Speed is more than 175 RPM higher than Desired Idle.

•	BARO above 65 kPa.

•	Engine run time is greater than 2 minutes.

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 and Failure Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been 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 the 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.

•	Vacuum leak. Check for a condition that causes a vacuum leak, such as disconnected or damaged hoses, leaks at EGR valve and EGR pipe to intake manifold, leaks at throttle body, faulty or incorrectly installed CRANKCASE VENTILATION valve, leaks at intake manifold, etc.

•	Throttle body. Check for a sticking throttle plate. Also inspect the IAC passage for deposits or objects which will not allow the IAC pintle to fully extend.

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

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. Refer to PCM Replacement/Programming .

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic System Check performed?

Go to Step 2

Go to Powertrain OBD System Check

Are any other DTC(s) set?

Go to other DTC first

Go to Step 3

Start engine.
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

No trouble found. Go to Diagnostic Aids.

Go to Step 4

Disconnect the IAC.
Install IAC Node Light J 37027 or equivalent.
With the engine running, command RPM up to 1500, down to 650, and then up to 1500 while observing the node light.

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 Engine Electrical).

Was a problem found?

Go to Step 11

Go to Step 9

Visually/physically inspect for the following conditions:

•	Vacuum leaks.

•	Throttle body tampering (Adjustment screw plug removed).

•	Throttle Plate or Throttle Shaft for binding.

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

•	Faulty, missing, or incorrectly installed CRANKCASE VENTILATION valve.

Does any of the above require a repair?

Refer 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 Engine Electrical).

Was a problem found?

Go to Step 11

Go to Step 8

Replace IAC valve.

Is 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 Engine Electrical).

Was a problem found?

Go to Step 11

Go to Step 10

Replace the PCM.

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

Is action complete?

Go to Step 11

Start engine.
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

Repair complete

Go to Step 2