What P0505 means
At idle, a small computer-controlled valve (or throttle motor on newer cars) meters exactly the air the engine needs to run unloaded. P0505 means idle speed won't obey — the control system commands and the engine idles wherever it can, which is where stalling and racing idle both come from.
What you’ll notice
- Stalling at stops or on startup
- Idle too high, too low, or hunting up and down
- Stumble when A/C or steering load hits
- Check engine light
Likely causes and repair cost
Broad US independent-shop bands, parts and labour.
Can you drive with P0505?
With stalling caveats — an engine that dies at stops takes power assist with it at bad moments. Book it promptly; the fix is often just a cleaning.
The misdiagnosis to avoid
Skipping the relearn. Many cars need an idle relearn procedure after cleaning or replacement — battery-disconnect rituals or scan-tool routines — and without it the 'fixed' car idles badly out of the gate, parts get blamed, and a second round of spending starts. Ask specifically whether yours needs one.
Describe what it’s doing in your own words and the symptom checker gives you a safe-to-drive verdict, ranked causes with costs, and notes to take to the shop — free, no sign-up.
Read the code yourself
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Check price on AmazonQuestions people ask
Why does it stall only when I turn the steering at parking speed?
Power steering load at idle is the heaviest sudden demand the idle system faces — the pump loads the engine and the idle control must instantly add air. A fouled valve adds it late, and the engine dips or dies precisely during parking maneuvers. That symptom is nearly a component name.
The idle races high instead — same system?
Same system, opposite failure: a valve stuck open (or a vacuum leak it can't close against) feeds too much idle air. High idle is less stall-prone but harder on the transmission at engagement and worth the same cleaning-first approach.