IAT reading permanently shows unrealistic cold temperature.
P0112 — also written PO112, P 0112, 0112 — is the OBD-II code for iat sensor circuit low input. Same code, same fix: this page covers every spelling of it.
This code means the ECU thinks the air going into your engine is boiling hot (usually because of a short circuit), common on Ford Transits and Vauxhall CDTi engines.
P0112 is a sensors fault code, typically costing £25–£180 to put right in a UK garage.
What P0112 actually feels like to drive
- The car feels 'flat' and sluggish, like the turbo isn't waking up properly.
- Fuel economy takes a nose dive—you'll notice you're getting 10mpg less than usual.
- Excessive black smoke out the back when you floor it on the A9.
- Engine management light (EML) on, sometimes with a 'Reduced Engine Power' message.
- Rough idling when you're sat at the lights once the engine is up to temperature.
What causes P0112?
- Short to ground
- Failed sensor
- Connector water ingress
UK vehicles that throw P0112 most often
- Ford Transit Custom 2.2 TDCi (2012-2016)
- Ford Focus 1.6 TDCi (DV6 engine) 2011-2015
- Vauxhall Astra J 1.7 CDTi (A17DTR) 2009-2014
- Vauxhall Insignia 2.0 CDTi (A20DTH) 2008-2017
- BMW 3 Series (E90/F30) 320d (N47 engine)
- Volkswagen Golf MK6 1.6 TDI (CAYC engine)
How P0112 is fixed
- Replace sensor
- Repair short
- Dry and reseal connector
The P0112 misdiagnosis that wastes money
I see folks rush to Euro Car Parts for a new sensor every single time they see P0112, but on the Transit Custom or the 1.6 TDCi Focus, it’s rarely the sensor itself. Nine times out of ten, we find the wiring loom has chafed through against a plastic bracket or the gearbox housing, grounding the signal wire. If you swap the sensor without checking the loom, you've just wasted thirty quid and an hour of your Saturday because that light will be back on before you’ve reached the end of the street.
What a UK garage should charge for P0112
A basic diagnostic plug-in will run you £40 to £60 at an indie like ours; main dealers will want £120 just to see the car. A genuine Bosch or Denso sensor is usually £25–£45 from a factor like GSF or Andrew Page. Fitting is quick—usually half an hour's labour (£30–£50). If we have to spend an hour chasing a broken wire in the loom and soldering it back together, you're looking at a total bill around the £120–£150 mark including VAT.
P0112 repair cost in the UK
Most P0112 repairs land between £25–£180 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 P0112
When you take it to a garage, don't just say "change the sensor." Ask them to do a 'live data' check on the scanner. If the IAT is stuck at 150°C even when the engine is stone cold, it's a dead giveaway for a short to ground. Also, tell them to 'wiggle test' the loom while watching the data. If the temp jumps around, it's a wiring job, not a sensor job. If it turns out you do need a sensor, stick with Bosch or NTK—don't buy the cheapest unbranded one from eBay or it'll mess with your fuel trims and you'll be failing the MOT smoke test.
Can you drive with P0112?
Yes.
Urgency: low.