Cat temperature sensor fault.
P0425 — also written PO425, P 0425, 0425 — is the OBD-II code for catalyst temperature sensor (bank 1). Same code, same fix: this page covers every spelling of it.
This code means the ECU has lost its mind regarding how hot the catalytic converter is getting. It's almost always a failed EGT sensor, common on modern Euro 5 and 6 diesel engines.
P0425 is a emissions fault code, typically costing £90–£400 to put right in a UK garage.
What P0425 actually feels like to drive
- Engine Malfunction Light (EML) staring you in the face on the dash.
- Car won't perform a DPF regeneration (on diesels), leading to 'DPF Full' messages.
- Limp mode kicks in, leaving you with zero power when trying to join the A9.
- Slightly heavier fuel consumption than usual.
- The cooling fans running at full blast even when the engine is cold.
What causes P0425?
- Failed sensor
- Wiring damage from exhaust heat
UK vehicles that throw P0425 most often
- Vauxhall Insignia 2.0 CDTi (A20DTH) 2008-2015
- Nissan Qashqai 1.5 dCi (K9K) 2013-2018
- Ford Focus 1.6 TDCi (DV6) 2011-2015
- Volkswagen Golf Mk7 2.0 TDI (CRBC) 2012-2017
- Land Rover Discovery Sport 2.0 TD4 (Ingenium) 2015-2019
How P0425 is fixed
- Replace sensor
- Repair loom with heat-resistant sleeving
The P0425 misdiagnosis that wastes money
I’ve seen dozens of lads rush out and buy a brand-new catalytic converter thinking 'Catalyst' means the cat is dead. They spend £600 on an aftermarket cat, fit it, and the EML pops right back on. It’s rarely the cat itself throwing this specific code; it’s usually just the probe that monitors it. We also see people changing the oxygen sensors (Lambda) by mistake. P0425 is strictly about the temperature probe, not the O2 levels. Don't throw a £500 cat at a £90 sensor problem.
What a UK garage should charge for P0425
A diagnostic plug-in at an indie will run you £50 to £80. A genuine Bosch or Denso sensor usually costs between £90 and £160 from a motor factor like Euro Car Parts or GSF. Labour is usually an hour (£60-£100), but if it’s seized into the exhaust—which they often are—expect to pay more for the heat and swearing required to get it out. At a main dealer, you won't see much change from £450.
P0425 repair cost in the UK
Most P0425 repairs land between £90–£400 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 P0425
If you take this to a garage, ask them to 'live data' the EGT (Exhaust Gas Temperature) sensors. If the sensor is reading a static -40°C or a constant 1000°C regardless of engine temp, it’s a dead giveaway. Don't let them just clear the code and send you off; these sensors often fail 'intermittently' when they get hot. Also, insist they check the wiring harness near the turbo heat shield—I’ve saved customers hundreds just by soldering a wire that had rubbed through on a sharp bracket.
Can you drive with P0425?
Yes.
Urgency: medium.