P0508

Idle Air Control System Circuit Low

Q: Is it safe to drive with P0508?

Be cautious. A low IAC circuit can cause stalling at idle or when stopping, which is unsafe in traffic. Get it repaired promptly.

Q: Can I just clear P0508?

It clears, but returns quickly if the IAC valve, its passage, or the wiring is still faulty. Fix the cause first.

Idle speed control Generic OBD-II High

What it means

P0508 means the idle-air control (IAC) circuit is reading lower voltage than expected, typically from a short to ground or a failing IAC valve. The IAC meters air around the throttle plate to hold a steady idle, so this fault often shows up as a rough idle or stalling when the engine drops to idle. It's worth fixing quickly because stalling can be unsafe.

High

Can I keep driving? Risky — a faulty idle-air control circuit can cause stalling at idle or in gear, so drive as little as possible until it's fixed.

Real-world scan data

Seen in

276

scans in the past year

Found in

<0.1%

of scans

0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Rough, low, or unstable idle
Stalling at idle, at stops, or when coming to rest
Hard to keep running right after start-up

Common causes

Most likely first

Short to ground in the idle-air control (IAC) circuit wiringLikely
Faulty IAC valve or motorCommon
Corroded or loose IAC connectorCommon
Carbon-clogged IAC passage restricting airflowLess often
ECM driver fault (least common)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data and note the idle conditions when the fault sets.
Inspect the IAC connector and wiring for a short to ground, corrosion, or damage.
Remove and inspect the IAC valve/passage for heavy carbon; clean or replace as needed.
Measure the IAC circuit resistance and voltage against spec to confirm a valve vs. wiring fault.
Replace the IAC valve if it tests bad; clear the code and confirm idle stabilizes.

FAQ

Quick answers

Is it safe to drive with P0508?+

Be cautious. A low IAC circuit can cause stalling at idle or when stopping, which is unsafe in traffic. Get it repaired promptly.

Can I just clear P0508?+

It clears, but returns quickly if the IAC valve, its passage, or the wiring is still faulty. Fix the cause first.

Read & clear P0508 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX