Idle RPM Running Higher Than Target
What does KOHLER-COMMAND-P0507 mean?
The KOHLER-COMMAND-P0507 (Kohler Command) diesel fault code means: Idle RPM Running Higher Than Target. This is a moderate severity code.
Common Symptoms
- Engine idles noticeably faster than normal at rest or after blade engagement disengaged
- RPM gauge or display holds above the expected idle target, typically above 1400 RPM at no load
- Engine feels like it wants to surge or hunt at low speed
- Mower deck or PTO engages with more jerk than usual due to elevated idle
- Fault code P0507 flashes via LED blink sequence or appears on equipment manufacturer dash
- Throttle response feels sloppy or unresponsive at low end
- Engine may be harder to bring down to a smooth idle after hard cutting
Probable Causes (Ranked by Likelihood)
- Vacuum leak at intake manifold, throttle body gasket, or any vacuum hose allowing unmetered air into the intake Very Likely
- Idle Air Control (IAC) valve stuck open or carboned up, unable to reduce airflow to lower RPM Very Likely
- Throttle plate not returning fully closed due to sticky throttle linkage, worn return spring, or debris in the throttle bore Likely
- Dirty or faulty throttle position sensor (TPS) sending an incorrect signal that causes ECU to over-command idle speed Likely
- Air filter housing seal damaged or missing, allowing unfiltered and unmetered air into the intake tract Possible
- ECU calibration drift or software issue causing idle target to be set too high after a wiring event or battery disconnect Possible
- Cracked intake boot or loose clamp between air filter and throttle body Less Likely
Step-by-Step Diagnostic Procedure
Start by checking all vacuum hoses connected to the intake manifold, throttle body, and any brake booster or accessory ports. Squeeze and flex each hose. A hissing sound at idle or a cracked hose is a strong sign of unmetered air entering the system.
Inspect the throttle body gasket and intake manifold gasket surfaces for cracks or gaps. With the engine running at idle, spray a small amount of carburetor cleaner around these gasket surfaces one at a time. If RPM changes when you spray a spot, you found a vacuum leak. Use this method carefully, away from ignition sources.
Check that the throttle linkage and throttle plate move freely and return fully to the closed position when the throttle lever is released. The plate should snap back with zero resistance. A weak or broken return spring will hold the plate cracked open and raise idle RPM above target.
Inspect the IAC valve. On Kohler EFI engines the IAC valve is typically mounted on or near the throttle body. Remove it and check the pintle for carbon buildup. A pintle that is stuck in the open position will not restrict airflow enough to lower idle. Clean the pintle and bore with throttle body cleaner and a soft brush.
Check the air filter housing and all clamps between the filter box and throttle body. Tighten any loose clamps and inspect the rubber intake boot for cracks. Even a small split in that boot lets unmetered air bypass the IAC and holds RPM high.
Using a multimeter set to DC voltage, backprobe the TPS signal wire with the key on and engine off. Voltage should read approximately 0.5 volts at closed throttle and rise smoothly to around 4.5 volts at wide open. A reading outside this range, or a jumpy signal, indicates a faulty TPS that may be feeding a false high-throttle signal to the ECU.
If all mechanical and vacuum checks pass, connect the Kohler PCM diagnostic tool for EFI models to read live data. Confirm the ECU's commanded idle target and actual idle RPM. If the ECU is commanding a high idle but no physical cause is found, a PCM recalibration or reflash by a Kohler-authorized dealer may be needed.
Frequently Asked Questions
What does Kohler Command code P0507 mean on my commercial mower?
P0507 means the ECU measured engine idle RPM higher than the programmed target. The engine is spinning too fast at low speed, usually because extra air is sneaking into the intake past a vacuum leak or because the IAC valve is stuck open and cannot bleed down the idle speed.
Can I still mow with a P0507 code active?
You can usually still operate the mower, but expect a rougher idle, possible surging, and a harsher PTO engagement. Running extended hours with a vacuum leak can lean out the mixture and cause premature engine wear, so diagnose and fix it soon rather than running through the season with it active.
How much does it cost to fix P0507 on a Kohler EFI engine?
If a vacuum hose or clamp is loose, the fix costs almost nothing. A replacement IAC valve runs $40-$90 in parts and is a DIY-friendly job for someone comfortable with basic hand tools. If the throttle body or TPS needs replacement, budget $80-$200 in parts. A dealer shop visit for diagnosis plus parts and labor typically runs $100-$350 total.
Will cleaning the IAC valve fix P0507 on my Kohler Command?
It often does, especially on engines with 500 or more hours that have never had the IAC serviced. Carbon buildup on the pintle is one of the most common causes. Clean it with throttle body cleaner, reinstall it, clear the code, and retest at idle. If the RPM stays high and the code returns, the valve itself may need replacement.