P0505 code meaning
Idle Control System
Powertrain system Generic code P05xx codes Check engine light
What P0505 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. P0505 is the general fault of the idle control, used where the maker does not separate too low from too high or the control is at its limit. With an idle valve it is typically sticking or gummed (Saab T5: idle outside 700–1200 rpm); on electronic throttles a Ford investigation shows P0505 from deposits in the throttle body. Ford's 2020–23 engines disable start-stop with P0505–P0507. Warning lamp behaviour depends on the maker.
P0505 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 P0505
- Idle speed fluctuates, too high or too low
- Engine stalls at idle or when coasting
- Start-stop not working
Common causes of P0505
- Most likelyThrottle body or idle valve dirty or gummed
- PossibleFalse air (hoses, intake gasket, crankcase ventilation)
- PossibleIdle valve faulty mechanically or electrically
- Less likelyLearned values not reset after cleaning
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 P0505 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. |
| 05 | The exact fault in that area. |
What to do next
- Note P0505 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 P0505
What does P0505 mean?
P0505 means "Idle Control System". 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 P0505?
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 P0505 fail an emissions test?
Yes, it can. P0505 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 P0505 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 P0505 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.