P0505 Idle air control system malfunction

Idle control system fault

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P0505 means the engine computer cannot hold the idle speed it wants. The car usually still drives, with a high, low or hunting idle. It becomes more urgent if the engine stalls at stops.

It gets more serious if:

  • Inspect soon: The engine stalls at idle or when coming to a stop, or is hard to start.

Source: how we rate severity

P0505 in short

P0505 means the engine computer cannot hold the target idle speed: it commands a change but the idle does not follow. Common causes are a dirty throttle body or idle air valve, a vacuum leak, or a lost idle relearn after the battery was disconnected. It is usually not urgent unless the engine stalls.

At idle, the engine computer controls how much air gets past the closed throttle, either with a separate idle air control valve on older engines or by moving the electronic throttle plate itself. It aims for a target speed and watches the result.

P0505 sets when the actual idle speed does not respond to what the computer commands. Carbon build-up around the throttle plate or in the idle air valve, an air leak after the throttle, or a lost learned idle position are the usual reasons. Ford notes that P0505, P0506, P2111 and P2112 can appear after the battery is disconnected on some 2004-2009 models until the idle is relearned.

Some cases are covered by bulletins: Ford for low idle and hard starting on 4.6L and 5.4L trucks, Toyota for 2GR-FE V6 engines, Nissan for an incorrect idle speed setting on 2000-2001 models, and Lexus for 2UR-GSE V8s, where a modified throttle body and ventilation hoses are installed.

Most likely causes

  1. Dirty or sticking throttle body or idle air control valve

    Supported by vehicle data
    Why it ranks here
    General references put carbon build-up first, owners report idle faults fixed by replacing the idle air valve or throttle body, and Lexus fixes P0505 on 2UR-GSE V8s with a modified throttle body.
    What would change this
    Rises with visible carbon at the throttle plate or a hunting idle; falls if the throttle is clean and the idle relearned.
    How to test the electronic throttle body

  2. Vacuum or intake air leak

    Common general cause
    Why it ranks here
    Unmetered air after the throttle raises idle beyond what the computer can control. One F-150 owner's P0505 stalling later traced to a leaking resonator hose.
    What would change this
    Rises with a high idle, hissing, or lean codes; falls if a smoke test finds no leak.
    How to test the vacuum hoses and intake leaks

  3. Idle not relearned after battery disconnect

    Supported by vehicle data
    Why it ranks here
    Ford TSB 12-7-4 lists P0505, P0506, P2111 and P2112 after a battery disconnect on many 2004-2009 Ford, Lincoln and Mercury models.
    What would change this
    Rises if the code appeared after battery or computer work; falls if no such work was done.

  4. Engine computer calibration or idle setting covered by a bulletin

    Supported by vehicle data
    Why it ranks here
    Ford (4.6L/5.4L low idle), Toyota (2GR-FE) and Nissan (incorrect idle speed setting) have bulletins naming P0505.
    What would change this
    Rises if your vehicle and engine are listed and the repair has not been done.
    How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Think back: did the code appear after the battery was disconnected or replaced, or after other engine work?

    Low risk

  2. With the engine off, look for cracked or loose vacuum and intake hoses, and check the throttle body for carbon build-up.

    Low risk

  3. Have a shop check for bulletins, smoke-test the intake for leaks and watch commanded versus actual idle on a scan tool.

    Best left to a shopTool: scan tool, smoke machine

    Warning:Testing is done with the engine running near moving belts and hot parts.

Symptoms

  • Check engine light
  • Idle too high, too low or hunting up and down
  • Rough idle
  • Stalling at stops or hard starting Gets more serious: stop and have it checked.

How to fix

  1. If the battery was recently disconnected, drive normally for a few days or ask a shop to run an idle relearn; Ford lists idle codes after battery work on many models.

  2. Check vacuum and intake hoses for cracks and loose clamps.

  3. Ask a dealer whether a bulletin covers P0505 on your vehicle.

Parts and cost context

  • Electronic throttle body:Often cleaned rather than replaced. Some bulletins (Lexus 2UR-GSE) install a modified part. Labor varies; get a quote.
  • Vacuum hoses and intake leaks:Cracked hoses are a common, cheap cause of idle faults.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Ford

  • 2004–2010 · F-150 · 4.6L, 5.4L

    Supported by vehicle data

    Ford bulletins cover low idle/hard start with P0505/P0506 and idle codes after a battery disconnect. A 2010 owner's stalling P0505 was treated with a new throttle body, later traced to a resonator hose leak.

  • 08-5-13Status unverified

    Ford TSB 08-5-13: 4.6L/5.4L low idle, hard start, P0506/P0505

    2004–2006f-150 · 4.6L, 5.4L · issued · NHTSA 10024828

    Low idle and hard starting with P0506 and/or P0505 on 4.6L and 5.4L engines.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • TSB-12-7-4Status unverified

    Ford TSB 12-7-4: P0505/P0506/P2111/P2112 after battery disconnect

    2004–2009f-150, mustang, explorer, crown-victoria, e-series, explorer-sport-trac · issued · NHTSA 10045340

    Idle codes may set after the battery is disconnected (only the summary was read).

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Nissan

  • 2000–2001 · Maxima

    Supported by vehicle data

    Nissan NTB00041 covers an incorrect idle speed setting on 2000 models; a 2001 owner reports a high idle fixed by replacing the idle air valve.

  • NTB00041Status unverified

    Nissan NTB00041: incorrect idle speed setting

    2000–2001maxima, sentra, pathfinder · issued · NHTSA 612640

    Idle speed may be set incorrectly; no drivability concern. Infiniti ITB00-030 matches.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Toyota

  • TSB-0184-09Status unverified

    Toyota TSB-0184-09: 2GR-FE P0505

    2005–2010camry, rav4, highlander, sienna, avalon, venza · 2GR-FE · issued · NHTSA 10032729

    P0505 on vehicles with the 2GR-FE V6.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0506Idle control system RPM lower than expected

    Same system Supported by vehicle data

    Ford lists P0505 and P0506 (idle lower than expected) together after a battery disconnect and for low idle on 4.6L/5.4L engines.

  • P2111The engine computer commanded the electronic throttle to close further but saw it stay more open than expected

    Same system Supported by vehicle data

    Ford TSB 12-7-4 lists P2111 (throttle stuck open) with P0505 after a battery disconnect; Lexus lists them together on 2UR-GSE.

  • P2112The engine computer commanded the electronic throttle to open but saw it stay more closed than expected

    Same system Supported by vehicle data

    Ford TSB 12-7-4 lists P2112 (throttle stuck closed) with P0505 after a battery disconnect.

  • P0507Idle speed higher than the computer is aiming for

    Same system Common general cause

    Both are idle control codes; P0507 is idle higher than expected.

All Vehicle speed, idle control and engine electrical codes

P0505 questions

Can a battery disconnect cause P0505?

Yes, on some vehicles. Ford lists P0505 with other idle codes after a battery disconnect on many 2004-2009 models until the idle is relearned.

Will cleaning the throttle body fix P0505?

Often, when carbon is the cause. If the code returns, check for vacuum leaks and bulletins before replacing parts.

Sources and review

  1. P0505: Idle Air Control System Malfunction — Kelley Blue Book
  2. Nissan NTB00-041: P0505 from incorrect idle speed setting, no drivability concern — Nissan North America / NHTSA ,
  3. NHTSA complaint ODI 10383032: 2010 Ford F-150, stalling, dealer replaced throttle body for P0505 — NHTSA Office of Defects Investigation (complaint flat file) ,
  4. Ford TSB 08-5-13: 4.6L/5.4L, P0506 and/or P0505, low idle, hesitation, hard starting — Ford Motor Company / NHTSA ,
  5. NHTSA complaint ODI 10185642: 2001 Nissan Maxima, high idle with P0505, idle air control valve replaced — NHTSA Office of Defects Investigation (complaint flat file) ,
  6. Lexus L-SB-0032-25: 2UR-GSE V8, P0505 and/or P2111, modified throttle body and ventilation hoses — Toyota Motor Sales / NHTSA ,
  7. Ford TSB 12-7-4: hard start and idle fluctuation with P0505/P0506/P2111/P2112 after battery disconnect — Ford Motor Company / NHTSA ,
  8. Toyota TSB-0184-09: 2GR-FE engines, MIL with P0505 — Toyota Motor Sales / NHTSA ,
Last reviewed
Written by
Saurabh K.
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