OBD-II Code · Fuel & Air
P0508
Idle Air Control Circuit Low
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$80–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
IAC voltage low.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Stalling
- Check engine light
Likely causes
- Wiring shortMost common
- Failed IAC
Read the full diagnostic procedureP0508 indicates the IAC control circuit is reading low voltage, typically a short-to-ground on the IAC driver wire or an internally shorted IAC solen…
P0508 indicates the IAC control circuit is reading low voltage, typically a short-to-ground on the IAC driver wire or an internally shorted IAC solenoid winding. The PCM detects that the commanded current exceeds the expected return and sets the code, often with the IAC disabled and idle dropping to a stall or surging.
Cheapest-first diagnosis
- key on engine off, disconnect the IAC and measure resistance across the solenoid terminals, a healthy 2-coil IAC reads roughly 8 to 14 ohms per coil (GM 4-pin) or 6 to 13 ohms single-coil (Ford 2-pin); anything under 4 ohms is a shorted winding and the IAC is the fault.
- With the IAC disconnected and the engine running, back-probe each driver wire at the PCM connector and read voltage, you should see roughly 7 to 10V key-on engine running on the driven pin.
- A flat 0V on a driver wire with the IAC unplugged means the wire is shorted to ground between the connector and the PCM. Check for chafed harness at the valve cover or at the intake manifold mounting bolts.
- The expensive misdiagnosis is replacing the PCM when a $25 IAC valve or a section of repair tape on the harness fixes it.
Vehicle-specific patterns1996 to 2002 GM 4.3L/5.0L/5.7L Vortec sets P0508 from an internally shorted IAC winding, the failure rate rises sharply past 100k miles.
- 1996to 2002 GM 4.3L/5.0L/5.7L Vortec sets P0508 from an internally shorted IAC winding, the failure rate rises sharply past 100k miles.
- 1997to 2003 Ford F-150 4.6L and 5.4L set P0508 from a chafed IAC harness at the upper intake bolt where the wire rubs through.
- 2000to 2005 Chrysler 3.3L/3.8L minivans set P0508 from a shorted IAC pigtail and water intrusion at the connector.
- 1998to 2002 Honda Accord 3.0L V6 sets P0508 from a failing IAC valve at the throttle body.
Estimated repair$35 to $220.
Look up another code
P0508 — frequently asked
What does a P0508 code mean?
IAC voltage low.
What causes a P0508 code?
Common causes: Wiring short; Failed IAC.
What are the symptoms of a P0508 code?
Typical symptoms: Stalling; Check engine light.
Is it safe to drive with a P0508 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $80-$400.
How do I diagnose a P0508 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
More free tools