P0506: Idle Control System RPM Lower Than Expected
Key takeaways
- P0506 means the engine idles slower than the target speed the computer is aiming for, and it can't bring the speed up.
- It's safe to drive, but a low idle can shake, stumble when the A/C kicks on, or stall at stops; stalling in traffic makes it more urgent.
- A carbon-choked throttle body and a skipped idle relearn are the most common causes; clean first, then relearn.
- Most fixes cost $50–$400; a new electronic throttle body is the expensive end at up to $700.
- GM bulletins for 1.5L turbo Equinox, Terrain and Malibu models trace P0506 to the charge air cooler duct coming off the throttle body.
What P0506 means
Your engine is idling slower than the computer wants, and it has run out of ways to bring the speed up. Scanners call it Idle Control System RPM Lower Than Expected. At idle the engine computer sets a target speed and controls it through the electronic throttle, or through a separate idle air control valve on older cars. If the actual RPM stays below the target by more than a set amount even after the computer has opened the idle air as far as it’s allowed, it stores P0506. In practice that usually means the engine can’t get enough air at idle, most often because of carbon in the throttle body.
Is it safe to drive?
Yes, in most cases, while you book a repair. You may feel the engine shake at stops, see the RPM dip when the A/C or headlights come on, or notice a rough idle in gear. The answer changes if the engine stalls, especially when you roll to a stop or turn the wheel at low speed. Losing the engine in traffic means heavier steering and brakes, so get it looked at within days, not weeks. If it’s also running rough or setting misfire codes like P0300, see car stalls while driving.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Dirty throttle body | Carbon ring behind the throttle plate; learned idle values at their limit | $80–$200 to clean and relearn |
| Idle relearn not done | Code appeared after a battery disconnect or throttle body work | $80–$200 with the relearn done at a shop; often $0 DIY |
| Intake air leak or loose duct after the airflow sensor | Hissing or a duct off the throttle body; airflow or lean codes too; smoke test finds it | $50–$400 |
| Sticking idle air control valve (older cars) | Idle doesn’t respond when the valve is commanded open | $150–$400 |
| Extra load or low voltage at idle | RPM drops with A/C or lights on; low or unsteady charging voltage | $150–$350 for a battery; more if charging is at fault |
| Failing electronic throttle body | Throttle position codes as well; plate sticks or responds slowly | $300–$700 |
| Engine software | Matching bulletin for your vehicle | $100–$200, often $0 under a bulletin |
What to check first
- Look at the throttle body. A heavy carbon ring behind the plate is the classic cause. Don’t hold a drive-by-wire throttle open by hand with the key on.
- Clean it, then do the idle relearn. After cleaning, a battery disconnect or a throttle body replacement, run the relearn for your make. Skipping it is a common reason P0506 comes right back.
- Check the intake ducts and hoses. On turbo engines, look for a charge air duct loose at the throttle body. On all engines, listen for a hiss and ask for a smoke test if nothing is obvious.
- Test the battery and charging voltage. Cheap to check, and a weak charge makes idle sag under electrical load.
- Clear it and drive. After each fix, clear the code and drive a few days to see if it returns.
The bulletins show clear patterns. GM has several for 2018–2022 Equinox, Terrain and Malibu models with the 1.5L turbo, where the charge air cooler duct comes off the throttle body, including an emission recall and a retainer kit. GM also flags P0506 with misfire codes on some 2020–2021 trucks, SUVs and Camaros as a possible valve spring concern, which is an engine problem, not an idle one. Ram and Jeep bulletins are mostly engine computer reflashes.
What it costs
The cheap outcome is a loose duct or hose, from about $50, or a throttle body cleaning plus relearn at $80–$200. The common outcome is that cleaning and relearn, or an air leak found with a smoke test at up to $400. The expensive outcome is a new electronic throttle body at up to $700. An hour of diagnosis, usually $100–$180, costs less than a throttle body you didn’t need. If you want a second opinion on your readings, ask our AI mechanic.
Related codes
P0506 is the low-idle twin of P0507 and sits in the same family as P0505 (idle control system). With a disconnected turbo duct it often comes with P0101, P0172, P0299 and P1101. For a shaky or uneven idle, see rough idle and car shakes at idle.
What owners report to NHTSA
16 complaints filed with NHTSA mention P0506, 15 of them since 2015, across 13 different models. The component owners most often filed it under: engine.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| KIA SORENTO | 3 | 2014, 2021 |
Manufacturer service bulletins that name P0506
141 technical service bulletins and manufacturer communications filed with NHTSA mention P0506, from 6 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- CHEVROLET EQUINOX (2018, 2019, 2020, 2021), bulletin 10201292: This Preliminary information communicates the possibility of the charge air cooler pipe connection becoming disconnected from the throttle body causing a reduced power issue and one or more of the following trouble codes…
- GMC TERRAIN (2018, 2019, 2020, 2021), bulletin 10201292: This Preliminary information communicates the possibility of the charge air cooler pipe connection becoming disconnected from the throttle body causing a reduced power issue and one or more of the following trouble codes…
- RAM 3500 (2020, 2022), bulletin 10214636: Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the Engine Control Module (ECM) / Powertrain Control Module (PCM) with the latest available software. Customers may experience a Malfunc…
- GMC TERRAIN NA (2022, 2018, 2019, 2020), bulletin 10226122: This service bulletin provides a repair procedure to correct a customer concern of Reduced Engine Power, Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0101, P0172, P0299, P0506, and/or P1101 Set.
- CHEVROLET CAMARO (2020, 2021), bulletin 10181159: This Preliminary information communicatesA Vehicle may have a concern of service engine light, misfire and engine noise with possible of DTC P0300 P0106 P0506, Possible valve spring concern
- GMC SIERRA 2500 (2020, 2021), bulletin 10181159: This Preliminary information communicatesA Vehicle may have a concern of service engine light, misfire and engine noise with possible of DTC P0300 P0106 P0506, Possible valve spring concern
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can I drive with a P0506 code?
Yes, in most cases. A slightly low idle is a nuisance, not damage. If the car shakes hard at stops, stumbles when the A/C comes on or stalls, get it fixed soon, because losing the engine in traffic also means heavier steering and brakes.
Can a dirty throttle body cause P0506?
Yes, it's the most common cause. Carbon builds up behind the throttle plate and chokes off the small gap idle air flows through. The computer opens the throttle further to compensate until it runs out of range, then sets P0506.
Do I need an idle relearn after cleaning the throttle body?
On most drive-by-wire cars, yes. The computer has learned to hold the throttle open further to make up for the carbon. Some cars relearn on their own over a few drives; others need a key-and-pedal sequence or a scan tool.
What's the difference between P0506 and P0507?
P0506 means idle is lower than the computer wants, P0507 means it's higher. Too-low usually points to a restriction such as carbon or an unlearned throttle; too-high usually points to extra air getting in, such as a vacuum leak.