Electronic throttle low input.
P0508 — also written PO5O8, P 0508, 0508 — is the OBD-II code for idle air control system — circuit low. Same code, same fix: this page covers every spelling of it.
This code means the ECU isn't seeing the voltage it expects from the idle control circuit, usually because the motor inside the throttle body is sticking or the wiring has rubbed through. It’s a classic headache on older Vauxhall Corsas and high-mileage Ford Zetec engines.
P0508 is a fuel & air fault code, typically costing £200–£700 to put right in a UK garage.
What P0508 actually feels like to drive
- The car 'hunts' for a steady idle, revs bouncing between 600 and 1200rpm at the lights.
- It stalls every time you dip the clutch coming up to a roundabout.
- Engine 'surges' slightly when you're just crawling in traffic.
- The 'Service Vehicle Soon' or EML light is glaring at you on the dash.
- It feels 'dead' or hesitant when you first touch the throttle from a standstill.
What causes P0508?
- Failed throttle body motor
- Wiring fault
UK vehicles that throw P0508 most often
- Vauxhall Corsa D 1.2/1.4 (A12XER/A14XER) 2009-2014
- Ford Fiesta 1.25/1.4/1.6 Sigma (Zetec) 2008-2017
- Fiat 500 1.2 8v (169A4000) 2007-2020
- Volkswagen Polo 1.2 3-cylinder (AZQ/BME) 2002-2009
- Nissan Qashqai 1.6 HR16DE 2007-2013
- Renault Clio 1.2 16v (D4F) 2005-2012
How P0508 is fixed
- Replace throttle body
- Repair loom
The P0508 misdiagnosis that wastes money
I see lads throwing new batteries or expensive ECUs at this one far too often because they see 'Circuit Low' and think the brains have fried. In the real world, nine times out of ten, it’s a gummed-up butterfly valve causing the motor to draw too much current, or the pins in the connector have turned green with corrosion. Don't go buying a new brain for the car until you’ve spent ten minutes with a can of Wynn’s Throttle Body Cleaner and a multimeter.
What a UK garage should charge for P0508
A proper diagnostic plug-in will cost you £50-£80 at an indie. If it’s just a dirty throttle body, we’d charge an hour’s labour (£60-£90) to strip and clean it. If the unit’s toast, a Bosch replacement is usually £150-£250 plus an hour to fit and calibrate. If you go to a main dealer, you won't get change from £600 once they’ve added their 'diagnostic fee' and marked up the OEM part. Total bill usually lands between £220 and £450 at my place.
P0508 repair cost in the UK
Most P0508 repairs land between £200–£700 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0508
If your garage says you need a whole new throttle body, ask them if they’ve 'load tested' the wiring back to the ECU. A simple continuity test isn't enough; you need to make sure the wires can actually carry the current. Also, insist on a Bosch or Pierburg replacement if it is the unit at fault. We’ve tried the £40 eBay specials and they usually pack up within a month, leaving you paying the labour twice. A proper scan tool should be able to perform an 'Idle Relearn' after the fix—if they can't do that, take it elsewhere.
Can you drive with P0508?
Yes but may go limp.
Urgency: medium.