Fix P0507: Mechanic’s solutions that WORKED

The code P0507: Idle Air Control System RPM Higher Than Expected points out a fault in the idle control system, and most likely is caused by issues with the cruise control cable or the Idle Air Control (IAC) valve.

P0507 quick overview

Meaning	P0507: Idle Air Control System RPM Higher Than Expected
Is it serious?	Moderate. While it might not cause immediate damage, it can lead to drivability issues and increased fuel consumption.
Possible causes	– Tight or misadjusted cruise control cable – Malfunctioning or dirty Idle Air Control (IAC) valve – Vacuum leaks – Collapsed PCV hose – Faulty Idle Speed Control (ISC) – Throttle body adjustments or carbon deposits
How to diagnose?	Check the Cruise Control Cable: Ensure it’s not too tight and adjust if necessary. Inspect the IAC Valve: Measure its resistance and clean if it’s dirty or clogged. Search for Vacuum Leaks: Use a smoke machine or listen for hissing sounds around the intake manifold. Examine the Throttle Body: Ensure no one has improperly adjusted the idle set screw and check for carbon deposits. Inspect PCV Hose: Ensure it’s not collapsed or damaged. Scan for Additional Codes: Sometimes, other related codes can provide more insights into the root cause. Consult Manufacturer’s TSBs: Check for any Technical Service Bulletins related to P0507 for the specific vehicle model.
What is IAC valve?	The IAC (Idle Air Control) valve regulates the engine’s idle speed by adjusting the amount of air bypassing the throttle plate, typically located near the throttle body.

How to fix P0507 – learn from mechanics

I looked into P0507 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Cadillac

1997 Cadillac Catera 3.0L

• Issue + repair history:
  • MIL (Check Engine Light) on.
  • Codes: P0411 (air) and P0507 (idle control).
  • Car came in 15 days prior with code P0411. Check valve was replaced, but the light came back on the next day. Now, code P0507 has also set.
  • Air pump showed signs of water staining and a leak, but worked when power was supplied directly.
  • Check valve was replaced 15 days ago.
• What are people suggesting to fix the issue:
  • One technician mentioned they couldn’t find a definition for code P0411 in their reference.
  • Suggested to clear the codes and check if they return immediately.
  • Mentioned that P0507 might have been set during diagnostics or due to another issue.
• Final fix:
  • The issue with P0411 was a vacuum supply problem. The dealer installed a check valve, but one of the lines was plugged. The end of the check valve was cut, the vacuum was reconnected, and the code was reset. No problems reported for 3 weeks after the fix.

Case #2: Chevrolet

2000 Chevrolet Malibu 3.1L

• Issue + repair history:
  • Intermittent stalling around 45 mph.
  • MIL (Check Engine Light) on with code po507.
  • Problem was duplicated once by the technician.
  • Only code in the system was po507.
  • Suspected crank sensor as the fault but couldn’t confirm.
• What are people suggesting to fix the issue:
  • One technician had a similar issue with a Malibu which was caused by a bad ignition switch. Mentioned that bad ignition switches are common in these vehicles.
  • Another technician agreed with the ignition switch suggestion.
  • A suggestion to scope the waveform pattern of the CKP (Crankshaft Position) sensor.
  • Possibility of Coolant Temperature Sensors causing intermittent stalls.
  • Check if the Anti-theft Light is flashing when the car won’t start.
  • Clear the code and drive until it stalls or won’t restart, then check for codes again.
• Final fix:
  • The ignition switch was the issue. The technician did a wiggle test on the wires to the switch and found that jarring it would shut down the car. Replacing the ignition switch solved the problem.

Case #3: Infiniti

2002 Infiniti I35 3.5L

• Issue + repair history:
  • Car initially came in for a routine spark plug change.
  • After a couple of days, the car returned with an idle speed error.
  • No leaks were found after smoking the intake.
• What are people suggesting to fix the issue:
  • Check the IAC valve for proper operation and consider cleaning the air passage and throttle body for carbon deposit.
  • Unplug the MAF sensor with the engine running, plug it back in, clear codes, and see if the problem is resolved.
  • Manual relearn procedures might help.
  • Some scanners like Vedis Autoland, Iscan 2, and possibly Snap-on might have the capabilities to do the relearns.
  • Consider replacing the IAC valve and possibly the ECM. If the IAC is replaced, take it to a dealer to set IAVL and avoid adjusting the throttle screw.
  • Check the connectors for the IAC to ensure they are plugged in properly.
  • Follow the throttle relearn procedure in the technical service bulletin (TSB).
• Final fix:
  • The car was sent to the dealer for ECU reprogramming, which resolved the issue. The technician is considering upgrading their scanner for future reprogramming tasks.

Case #4: Kia

2005 Kia Sedona EX 3.5L

• Issue + repair history:
  • The vehicle had drivability issues.
  • The throttle position revolutions were higher than expected.
• What are people suggesting to fix the issue:
  • The code might be related to the idle speed actuator located on the throttle body.
  • Check for a vacuum leak or a potentially bad actuator.
  • The problem might not be the valve, which is on the throttle housing. The ECU indicates the valve is completely closed, but RPM at idle is still higher than specs. A sticky throttle or manifold leak could be the issue.
  • Inspect the throttle assembly for carbon or resin. If found, perform an induction cleaning. If the vehicle has a drive-by-wire system, the spring inside might be causing the issue, and the whole unit might need replacement.
• Final fix:
  • The throttle body was full of carbon and was sticking on the back side. After cleaning, the issue was resolved.

Case #5: Hyundai

2002 Hyundai Santa Fe 2.4L

• Issue + repair history:
  • The car displayed the MIL (Malfunction Indicator Lamp) with code P0507.
  • The idle speed on the scan tool was high, approximately 900/1100 rpm in park.
  • No vacuum leaks were found during the initial inspection.
  • The resistance of the IAC (Idle Air Control) was measured, and there was a discrepancy in the force when jumpering the valve.
• What are people suggesting to fix the issue:
  • The P0507 DTC stands for “Idle Air control System RPM Higher Than Expected.”
  • Check for a binding throttle cable or a faulty idle control valve.
  • Ensure the throttle or cruise control cable isn’t causing the throttle to remain slightly open.
  • A tight cruise control cable might be positioning the throttle plate slightly open.
  • A collapsed PCV hose or a bad ISC might be the cause.
  • Adjusting the cruise control cable to create a slight slack might help.
  • Cleaning the idle air control valve might resolve the issue.
  • Check the adjustment on the throttle body if someone had previously tried to adjust the idle speed.
• Final fix:
  • The issue was with the cruise control cable; it was too tight. Adjusting the cable resolved the problem.