Air valve wiring shorted.
P0414 — also written PO414, P 0414, 0414 — is the OBD-II code for secondary air injection switching valve a — shorted. Same code, same fix: this page covers every spelling of it.
This code means the ECU has spotted a short circuit in the solenoid that controls the extra air pumped into your exhaust to heat the cat up. It's a classic headache on older Vauxhalls and high-mileage VWs.
P0414 is a emissions fault code, typically costing £120–£500 to put right in a UK garage.
What P0414 actually feels like to drive
- Engine management light (EML) glowing on the dash, usually after a cold start.
- A weird 'hissing' or 'whirring' sound for the first 60 seconds after turning the key.
- The car feels slightly 'flat' or sluggish during the warm-up phase.
- Failed MOT on emissions if the tester catches the EML on.
- A faint smell of 'off' eggs or raw exhaust near the front of the car in the morning.
What causes P0414?
- Wiring short
- Failed valve
UK vehicles that throw P0414 most often
- Vauxhall Astra H 1.6/1.8 VVT (Z16XER/Z18XER) 2005-2010
- Volkswagen Golf Mk4/Mk5 1.6 & 2.0 (AZJ/BGU) 2000-2008
- Audi A4 1.8T (B6/B7) 2001-2008
- Mercedes-Benz C-Class (W203/W204) M271 Engine 2002-2012
- Skoda Octavia 2.0 FSI 2004-2009
How P0414 is fixed
- Replace valve
- Repair wiring
The P0414 misdiagnosis that wastes money
I see DIYers and even some junior techs jump straight to swapping the air pump itself because it sounds like a vacuum cleaner from hell, but that's a £300 mistake. They also tend to throw a cheap 'pattern' relay at it from eBay. Nine times out of ten, the solenoid valve has suffered internal insulation failure, or the wiring harness has rubbed raw against the subframe or gearbox casing, causing a direct short to ground. Don't buy a pump until you've checked the resistance at the valve plug.
What a UK garage should charge for P0414
Expect to pay £60-£90 for a proper diagnostic plug-in and circuit test. A genuine Bosch or Pierburg switching valve usually runs between £80 and £180 depending on the model. Labour is typically an hour—call it £70 in an indie or £150 at a main dealer. If the wiring harness needs a loom repair, add another £50 for materials and time. You're looking at a total bill between £220 and £450 at a fair UK garage.
P0414 repair cost in the UK
Most P0414 repairs land between £120–£500 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 P0414
If your local garage says they want £600 to 'investigate', tell them to start with a simple resistance test on the N112 solenoid (if it's a VAG car). A healthy valve should show about 25-35 ohms. If it’s near zero, it's shorted. Also, insist they check for moisture in the connector; these valves often leak internally, letting exhaust condensate rot the pins. If you're out of warranty, ask about a Pierburg replacement—they’re the OEM for many German brands and half the price of the part in a branded dealer box.
Can you drive with P0414?
Yes.
Urgency: low.