P0506 Idle control system RPM lower than expected

Idle speed too low

Monitor

P0506 means the engine idled noticeably slower than the engine computer wanted for several seconds. On its own it is an idle-control fault rather than an immediate danger, so you can usually drive while you book a check. Watch for stalling, noise or overheating, which change that.

It gets more serious if:

  • Inspect soon: The engine stalls at idle or after an auto start-stop restart, or drops into reduced power. GM bulletins for P0506 describe stalls at low speed or idle. Get it inspected soon and leave extra room when stopping in traffic.
  • Stop: The engine misfires with a new ticking, clattering or knocking noise. GM links P0506 with P0106 on some V8s to a broken valve spring, and one owner reports bent pushrods. Stop driving and have it towed to avoid engine damage.
  • Stop: Steam or vapour comes from the grille or under the hood, or the temperature gauge climbs. GM links P0506 on the 2014 Impala to steam from the grille area. Pull over, stop the engine and let it cool; never open a hot radiator cap.

Source: how we rate severity

P0506 in short

P0506 means the engine idled slower than the engine computer's target, typically by about 100 rpm or more for several seconds. Common causes are a dirty throttle body, an intake air leak, lost idle learning after a battery disconnect, or software. Check bulletins and the throttle body first. Monitor it, but get it checked if the engine stalls.

At idle the engine computer sets a target speed and adjusts the air let past the throttle (with an electronic throttle or an idle air valve) to hold it. P0506 sets when actual idle stays too far below the target.

Regulations treat idle control as failed when it cannot get within 100 rpm below or 200 rpm above target. GM's test, for example, needs a warm engine idling with the car stopped, and sets the code when idle is about 94 rpm low for 10 seconds.

Because the computer can only add so much air, anything that chokes the airflow or adds load can pull the idle down: carbon in the throttle bore, lost idle learning, an intake leak on a turbo engine, or a mechanical engine problem.

Most likely causes

  1. Dirty throttle body or idle air passage

    Common general cause
    Why it ranks here
    The idle control system can only open the throttle or idle valve so far. Carbon build-up restricts the small idle opening, so the computer runs out of range and idle sags.
    What would change this
    Rises if the throttle bore is coated with carbon or the commanded idle airflow is near its limit; falls after cleaning if the code returns.
    How to test the electronic throttle body

  2. Idle learning lost after a battery disconnect or dead battery

    Supported by vehicle data
    Why it ranks here
    Ford has a bulletin for hard starts, idle fluctuation and P0505/P0506 on many 2004-2009 models after the battery was disconnected or went flat.
    What would change this
    Rises if the code appeared soon after battery work or a dead battery.
    How to test the engine control module (ecm / pcm)

  3. Charge air cooler duct off the throttle body (2019 Equinox, Malibu, Terrain)

    Supported by vehicle data
    Why it ranks here
    GM found the charge air cooler outlet can come off the throttle body, setting P0506 with boost and airflow codes, reduced power and stalling.
    What would change this
    Applies to the listed vehicles; rises with P0299, P0101 or P1101 stored and a loose or detached duct.
    How to test the electronic throttle body

  4. Crank sensor signal interference (2018 Enclave and Traverse)

    Supported by vehicle data
    Why it ranks here
    GM traced low idle, stalling after auto start and P0506 with cam correlation codes to interference on the crank sensor circuit, fixed with a new harness section.
    What would change this
    Applies to the listed vehicles; rises with P034B or P0011-P0024 also stored.
    How to test the crankshaft position sensor

  5. Broken valve spring (GM V8 engines)

    Supported by vehicle data
    Why it ranks here
    GM tells technicians who find P0106 with P0506 on several 2014-2019 trucks, SUVs and cars to inspect for a broken valve spring.
    What would change this
    Rises with P0106 stored, a misfire or a ticking noise.

  6. Low idle on 2004-2006 F-150 4.6L/5.4L

    Supported by vehicle data
    Why it ranks here
    Ford has a bulletin for P0506 and/or P0505 with hesitation, loss of rpm, hard starting and low idle on these trucks.
    What would change this
    Applies to the listed trucks; ask a dealer for TSB 08-5-13.

What to test first

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

  1. Read all stored codes and the freeze-frame data, and note anything that happened recently, such as battery work or a dead battery.

    Low riskTool: scan tool

  2. With the engine off, remove the intake duct and look into the throttle bore for carbon build-up; check the intake ducts and clamps between the air filter, turbo (if fitted) and throttle.

    Low riskTool: flashlight, hand tools

  3. Have a shop check for bulletins and compare actual and desired idle on a scan tool with the engine warm.

    Best left to a shopTool: scan tool, service information

    Warning:Idle checks need the engine running in a well-ventilated area, with the parking brake on and hands clear of moving parts. Leave this to a shop.

Symptoms

  • Low or uneven idle
  • Rough idle or vibration at a stop
  • Hesitation pulling away
  • Engine stalls at idle Gets more serious: stop and have it checked.
  • Ticking or clattering noise with misfire Gets more serious: stop and have it checked.
  • Steam from the grille or under the hood Gets more serious: stop and have it checked.

Compare with: Rough idle with the check engine light on

How to fix

  1. Write down every stored code and the freeze-frame data before clearing anything.

  2. If the code appeared after battery work, follow the idle relearn procedure in the owner's or service manual, or have a shop do it.

  3. Clean a carbon-coated throttle body only if the service information allows it, using throttle body cleaner, with the ignition off.

    Warning:On electronic throttles, do not push the throttle plate open by hand with the ignition on; it can move suddenly and pinch fingers.

Parts and cost context

  • Electronic throttle body:Cleaning often fixes a carbon-restricted throttle; replacement is only needed if it fails a test.

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

Compare used part prices on PartPriceGuide

On your vehicle

Ford

  • 2004–2006 · F-150 · 4.6L, 5.4L

    Supported by vehicle data

    On the 4.6L and 5.4L, Ford has a bulletin for low idle with P0506 (TSB 08-5-13).

  • 08-5-13Status unverified

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

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

    Hesitation, loss of rpm, difficulty starting and low idle with P0506 and/or P0505 on the 4.6L and 5.4L. Also lists the 2006 Lincoln Mark LT.

    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: hard start and idle fluctuation after battery disconnect

    2004–2009f-150, explorer, mustang, crown-victoria · issued · NHTSA 10045340

    Hard starts and idle fluctuation with P0505, P0506, P2111 or P2112 after the battery was disconnected or went dead, on various 2004-2009 Ford, Lincoln and Mercury models.

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

Chevrolet

  • 2014–2019 · Silverado 1500

    Supported by vehicle data

    With P0106 and P0506 together, GM says to inspect for a broken valve spring (PIP5423B).

  • 2019 · Equinox

    Supported by vehicle data

    A charge air cooler duct can come off the throttle body, causing P0506, reduced power and stalling (N192266090).

  • 2019 · Malibu

    Supported by vehicle data

    A charge air cooler duct can come off the throttle body, causing P0506, reduced power and stalling (N192266090).

  • 2018 · Traverse

    Supported by vehicle data

    Low idle and stalling after auto start with P0506 can come from crank sensor circuit interference (17-NA-317).

  • 2014 · Impala

    Supported by vehicle data

    GM has an information bulletin for steam from the grille, rough running or stalling with P0506 (PI1203B).

  • PIP5423BStatus unverified

    GM PIP5423B: P0106 and P0506, inspect for broken valve spring

    2014–2019silverado-1500, tahoe, suburban · issued · NHTSA 10160647

    With P0106 and P0506 set, inspect for a broken valve spring. Also lists Sierra 1500, Yukon, Escalade, Camaro, Corvette and CTS.

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

  • N192266090Status unverified

    GM N192266090: charge air cooler outlet disconnected from throttle body

    2019equinox, malibu · issued · NHTSA 10165446

    Reduced power, rough running and possible stalling with codes including P0506; dealers fit a retainer kit. Also covers the GMC Terrain.

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

  • 17-NA-317Status unverified

    GM 17-NA-317: low idle, stall after auto start, P034B/P0506

    2018traverse · issued · NHTSA 10190246

    Crank sensor circuit interference causes low idle, stalling after auto start and codes including P0506; the crank sensor harness section is replaced. Also covers the 2018 Buick Enclave.

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

  • PI1203BStatus unverified

    GM PI1203B: steam from grille, runs rough or stalls, P0506

    2014impala · issued · NHTSA 10113610

    Steam or vapour from the front grille or radiator area, rough running or stalling, or P0506. Repair details not in NHTSA's summary.

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

GMC

  • 2019 · Terrain

    Supported by vehicle data

    A charge air cooler duct can come off the throttle body, causing P0506, reduced power and stalling (N192266090).

  • N192266090Status unverified

    GM N192266090: charge air cooler outlet disconnected from throttle body

    2019equinox, malibu · issued · NHTSA 10165446

    Reduced power, rough running and possible stalling with codes including P0506; dealers fit a retainer kit. Also covers the GMC Terrain.

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

Buick

  • 2018 · Enclave

    Supported by vehicle data

    Low idle and stalling after auto start with P0506 can come from crank sensor circuit interference (17-NA-317).

  • 17-NA-317Status unverified

    GM 17-NA-317: low idle, stall after auto start, P034B/P0506

    2018traverse · issued · NHTSA 10190246

    Crank sensor circuit interference causes low idle, stalling after auto start and codes including P0506; the crank sensor harness section is replaced. Also covers the 2018 Buick Enclave.

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

  • P0507Idle speed higher than the computer is aiming for

    Same system Common general cause

    P0507 is the opposite fault: idle higher than expected. Both come from the same idle control system.

  • P0106Manifold pressure (MAP) sensor reading doesn't match what the engine computer expects

    Shares causes Supported by vehicle data

    On some GM V8s, P0106 with P0506 points to a broken valve spring.

  • P0299Turbocharger or supercharger is producing less boost than the engine computer requested

    Shares causes Supported by vehicle data

    On 2019 Equinox, Malibu and Terrain, a detached charge air cooler duct can set P0299 with P0506.

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

    Shares causes Supported by vehicle data

    Ford lists P2111 with P0506 after a battery disconnect on many 2004-2009 models.

All Vehicle speed, idle control and engine electrical codes

Sources and review

  1. 2011 Saab 9-4X V6 (GM): DTC P0506 or P0507 — General Motors / Saab Automobile (read via saabwisonline.com)
  2. Final Regulation Order: 13 CCR §1968.2, Malfunction and Diagnostic System Requirements (OBD II), 2004 and subsequent model-year passenger cars, light-duty trucks and medium-duty vehicles (2015 amendments) — California Air Resources Board
  3. GM N192266090: charge air cooler outlet disconnected from throttle body — General Motors / NHTSA ,
  4. GM 17-NA-317: low idle, stall after auto start, P034B/P0506 — General Motors / NHTSA ,
  5. 2023 Integra Owner's Manual: Indicator, Coming On/Blinking — American Honda Motor Co.
  6. GM PIP5423B: P0106 and P0506, inspect for broken valve spring — General Motors / NHTSA ,
  7. NHTSA complaint ODI 11702112: 2017 GMC Yukon XL, P0106/P0506 with broken valve spring and bent pushrods — NHTSA Office of Defects Investigation (complaint flat file) ,
  8. GM PI1203B: steam from grille, runs rough or stalls, P0506 — General Motors / NHTSA ,
  9. 2023 Integra Owner's Manual: How to Handle Overheating — American Honda Motor Co.
  10. Troubleshoot Idle Speed Control System — AA1Car.com (Larry Carley)
  11. TSB-12-7-4: Hard start and idle fluctuation after battery disconnect, P0505/P0506/P2111/P2112 — Ford Motor Company / NHTSA ,
  12. Ford TSB 08-5-13: 4.6L/5.4L P0506 and/or P0505, low idle — Ford Motor Company / NHTSA ,
Last reviewed
Written by
Saurabh K.
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