P0505: Idle control system malfunction
The ECU cannot control idle speed properly. Usually a dirty throttle body or idle valve, an air leak or an electrical fault.
| Code | P0505 |
|---|---|
| System | Engine and transmission |
| Group | P05xx, Speed, idle and auxiliary inputs |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0505 means
At idle the ECU adjusts how much air gets in to keep the engine turning at a steady speed. Depending on the car it does this with an idle air control valve or the electronic throttle itself. This code means the system is not responding as the ECU expects.
Most common causes
- Throttle body or idle valve coated in carbon
- Air leak from a vacuum hose or intake gasket
- Loose or corroded connector on the idle valve or throttle
- Faulty idle valve or throttle motor
- Throttle not relearned after cleaning or disconnecting the battery
Symptoms
- Idle too high, too low or hunting up and down
- Engine stalling when stopping or when the air conditioning comes on
- Hard starting
- Engine warning light on
Can you drive with P0505?
With care You can drive, but stalling at junctions or roundabouts can be dangerous. Get it fixed soon.
How to check it
Watch live idle speed and the idle valve or throttle opening value. If the opening is well above normal, there is usually dirt or an air leak. After cleaning the throttle, many cars need a relearn.
How to read and clear P0505 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0505 with this same explanation and whether it’s confirmed, pending or permanent.
With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.
Similar codes
- P0501 Vehicle speed sensor range/performance
- P0502 Vehicle speed sensor circuit low input
- P0503 Vehicle speed sensor intermittent, erratic or high
- P0504 Brake switch A/B correlation
- P0506 Idle speed lower than expected
- P0507 Idle speed higher than expected
- P0513 Incorrect immobiliser key
- P0520 Oil pressure sensor/switch circuit malfunction
- P0500 Vehicle speed sensor malfunction
- P0521 Oil pressure sensor/switch range/performance
- P0522 Oil pressure sensor/switch low voltage
- P0523 Oil pressure sensor/switch high voltage
P0505 is a generic code, so it means the same on any make, for example on Alfa Romeo, Dacia, Kia, Opel / Vauxhall, Toyota, Škoda. See what Final OBD does on your car in makes and models.
What does code P0505 mean?
At idle the ECU adjusts how much air gets in to keep the engine turning at a steady speed. Depending on the car it does this with an idle air control valve or the electronic throttle itself. This code means the system is not responding as the ECU expects.
Can you drive with P0505?
You can drive, but stalling at junctions or roundabouts can be dangerous. Get it fixed soon.
How do you clear P0505?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0505 comes back.
Read it on your car
Final OBD reads the faults of every control unit for free, including each make’s own codes, and with Pro explains each one in plain English. Free clears engine faults at no cost.
Coming soon
Mid to late October 2026
If you want to try it in your car before anyone else, send us your email and we will add you as a tester.
info@finalobd.com