P0506 code meaning
Idle Control System RPM - Lower Than Expected
Powertrain system Generic code P05xx codes Check engine light
What P0506 means
CARB requires the idle speed control to be monitored: gasoline engines must flag a fault if the target idle speed is not reached within +200/−100 rpm, diesels within ±30 %. Older engines use a separate idle air control valve that bypasses the closed throttle; with electronic throttle the throttle itself controls idle and no separate valve exists. P0506 means the idle speed of the warm engine at standstill stays too low despite fully used control. GM uses more than 91 rpm filtered for 10 s (MIL after two trips), Ford gasoline −100 rpm plus a correction above 1 lb/min, Ford diesel −100 rpm for 5 s, Subaru −100 rpm with the correction at its limit for 10 s three times. Typical are deposits, extra load or a restricted intake or exhaust.
P0506 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P0506
- Idle too low, engine shakes
- Engine stalls when stopping or with A/C on
- Check engine light after two trips
Common causes of P0506
- Most likelyDeposits at the throttle or bypass channel, or gummed idle valve
- PossibleExtra load: stiff accessory drive, gearbox or converter
- PossibleIntake or exhaust restricted (air filter, catalyst)
- PossibleIdle valve or throttle actuator faulty, wrong learned value
- Less likelyMechanical engine damage (low compression)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Idle controlThrottle bodyIdle air control valveEngine control module
What each part of P0506 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 06 | The exact fault in that area. |
What to do next
- Note P0506 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0506
What does P0506 mean?
P0506 means "Idle Control System RPM - Lower Than Expected". CARB requires the idle speed control to be monitored: gasoline engines must flag a fault if the target idle speed is not reached within +200/−100 rpm, diesels within ±30 %. It is a generic code, so it means the same on every make.
Is it safe to drive with P0506?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0506 fail an emissions test?
Yes, it can. P0506 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0506 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0506 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.