Ok... I keep getting a SES and a 507 (High Idle). I clear the codes and it's back in a couple of days. I did change out the IAC, but it didn't help.

Question I have is... If I took the car to the Buick dealer and told them to find the problem and fix it, what procedure would they use to find it?
I'm sure that there are some sort of trouble code diagnostic procedures somewhere.

I'd appreciate any guidance.

TIA
Giff

I would look for vaccum leaks on the engine! Most high idle problems are caused by air entering the engine downstream of the MAF sensor.

Every tech has a different way to tackle the problem, no one way is right. GM does have a general guideline trouble tree for your code but most techs thru experience learn quicker and easier ways to find the problem.

To you it should be more important that the dealer finds and fixes the problem then how they find the problem. Most techs do not like people watching them to learn hoew to fix a car, so be nice ask any questions you may have and let them fix your car!

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DTC P0507 Idle Speed High




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 lower number of counts indicates less commanded airflow (pintle extended). 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 Running the DTC
No VSS, TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, fuel trim, fuel injector, EGR pintle position, ECT sensor, CKP sensor, or MAF sensor DTCs set.
BARO is greater than 65 kPa.
Engine has been running for at least 2 minutes.
System voltage is between 9 and 16 volts.
Engine Coolant Temperature is greater than 70°C (158°F).
Vehicle Speed is less than 3 MPH.
Intake Air Temperature is greater than -18°C (0°F).
The throttle is closed.
Conditions for Setting the DTC
Engine Speed is more than 175 RPM higher than Desired Idle (positive idle speed error greater than 175 RPM).
Above conditions for longer than 15 seconds.
Action Taken When the DTC Sets
The PCM will illuminate the 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 Fail Records data.
Conditions for Clearing the MIL/DTC
The PCM will turn the MIL OFF 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 Clear Info function or by disconnecting the PCM battery feed.
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, malfunctioning or incorrectly installed PCV 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
Numbers below refer to 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 being replaced, the new PCM must be programmed.

DTC P0507 - Idle Air Control System RPM High Step
Action
Values
Yes
No

1
Was the Powertrain On-Board Diagnostic System Check performed?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2
Are any other DTCs set?
--
Go to Diagnostic Aids and diagnose the other DTCs first
Go to Step 3

3
Start the engine.
Turn OFF all accessories (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 Speed for each RPM command?
± 100 RPM
Go to Diagnostic Aids
Go to Step 4

4
Disconnect the IAC.
Install a J 37027-A IAC System Monitor.
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

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 in Wiring Systems.
Was a problem found?
--
Go to Step 11
Go to Step 9

6
Visually/physically inspect for the following conditions:
Vacuum leaks
Throttle body tampering (throttle lever stop screw turned)
Throttle plate or throttle shaft for binding
Binding of the accelerator control cables
Misadjusted accelerator control cables Refer to Accelerator Controls Cable Replacement .
Binding of the cruise control cables
Misadjusted cruise control cables Refer to Cruise Control Cable Replacement .
Missing PCV valve
Incorrectly installed PCV valve
Malfunctioning PCV valve Refer to Crankcase Ventilation System Inspection .
If a problem is found, repair as necessary.
Was a problem found?
--
Go to Step 11
Go to Step 7

7
Check for a poor connection at the IAC harness connector.
If a problem is found, replace terminals as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Was a problem found?
--
Go to Step 11
Go to Step 8

8
Replace the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement .

Is action complete?
--
Go to Step 11
--

9
Check for a poor connection at the PCM harness connector.
If a problem is found, replace terminals as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Was a problem found?
--
Go to Step 11
Go to Step 10

10

Important:
The replacement PCM must be programmed.


Refer to PCM Replacement/Programming .

Replace the PCM.

Is action complete?
--
Go to Step 11
--

11
Start engine.
Turn OFF all accessories (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 Speed for each RPM command?
± 100 RPM
System OK
Go to Step 2



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Thanks for the replies... 99SSCONV, that's exactly what I needed.

I didn't plan on taking my car to the dealer, I just need to know how the Buick dealer would approach the problem so I can proceed to fix it myself.

Thanks
Giff

What this code means is that the parameters compared to create the code do not match. Aside from looking for vacuum leaks, a misadjusted throttle body could cause this condition. So could problems with the MAF since the indicated air flow may not match the actual airflow. I would carefully check for vacuum leaks, then check the throttle stop settings, and carefully clean the throttle body. let me know... Ray

NOw I have to know since now you have the GM trouble tree for your problem did it help you out?

Its awful hard to follow a GM trouble tree without having the right test tools and scanner to perform the tests asked for.