A 2012 Honda Accord IX Sedan came in with a single P0507 code and a technician note that simply read "Las rpm está 1500". The engine, a K24W1, was idling at 1500 RPM, which is well above the commanded target.
The primary suspect is carbon buildup
The diagnostic engine we build ranked a dirty electronic throttle body as the most likely cause at 90 percent probability. Carbon builds up on the throttle plate and bore, preventing the plate from fully closing to its commanded position. This allows unmetered air into the intake manifold. The Engine Control Module often compensates for this gradual buildup by adjusting its learned idle position. If a recent battery disconnection or software calibration clears those learned values, the system suddenly detects more airflow than commanded and sets the P0507 code. The recommended tests here are a visual inspection of the bore and plate, monitoring Throttle Position Sensor live data for smooth operation, and cleaning the unit.
Hunting for unmetered air
If the throttle body is clean, the next logical step is finding a vacuum leak. This ranked at 85 percent probability. Any leak downstream of the throttle body allows unmeasured air into the engine, causing it to run lean and idle high. This could be a cracked vacuum hose, a degraded intake manifold gasket, a brake booster hose, or a faulty EVAP purge valve. Finding this requires a visual and audible inspection, followed by a smoke test and monitoring Short Term Fuel Trim live data.
A specific variation of the vacuum leak is a stuck open Positive Crankcase Ventilation valve, which ranked at 70 percent probability. This is a known common problem for K24 engines due to their oil vapor routing. The valve gets clogged with oil sludge and sticks open, acting as a persistent vacuum leak. A simple rattle test and visual inspection of the valve and hose usually confirm this.
The missed software step
Mechanical fixes sometimes create software problems. A failed or skipped idle relearn procedure ranked at 80 percent probability. On the K24W1 engine, the ECM stores learned values for the throttle plate position. If someone cleans the throttle body without performing the official Honda idle relearn procedure, the ECM commands a position that allows too much air through the now-clean system. Checking the vehicle service history and executing the relearn procedure solves this.
Do you see this same pattern of missed relearns causing high idles in your own bays?
Reference pages for the codes in this article
- P0507, what we measure for this code across real diagnostics