The rearmost oxygen sensor on bank 1 has a circuit fault.
P0142 — also written PO142, P 0142, 0142 — is the OBD-II code for o2 sensor circuit malfunction (bank 1, sensor 3). Same code, same fix: this page covers every spelling of it.
This code means the third oxygen sensor—usually found only on big luxury cruisers or older Euro 4 petrols—has a wiring or internal fault. It’s common on V6 Jaguars and old Land Rover Freelanders where the rear sensor takes a beating from the weather.
P0142 is a emissions fault code, typically costing £90–£320 to put right in a UK garage.
What P0142 actually feels like to drive
- Engine management light (EML) staring you in the face on the dash.
- A slight drop in MPG, though usually not as bad as a front sensor failure.
- A subtle 'ticking' or 'hissing' sound from under the car if it's an exhaust leak.
- Failing the MOT on emissions (specifically the Lambda reading).
- The car feels slightly 'flat' when cruising at motorway speeds.
What causes P0142?
- Failed O2 sensor
- Damaged wiring
- Exhaust leak upstream
UK vehicles that throw P0142 most often
- Jaguar XF 3.0 V6 Petrol (2008-2015)
- Land Rover Freelander 2 3.2 i6 (2006-2012)
- Vauxhall Omega 2.5/3.0 V6 (historic but common for this)
- BMW 5 Series (E60) 530i N52 engine
- Audi A8 4.2 V8 (D3 chassis)
How P0142 is fixed
- Replace O2 sensor
- Repair loom
- Fix exhaust leaks
The P0142 misdiagnosis that wastes money
I see folks throwing brand new Bosch sensors at this constantly, only to find the light pops back on three miles down the road. Because Sensor 3 is the 'watchdog' right at the back of the system, it's the most exposed to road salt and grit. Usually, the fault isn't the sensor's internal cell, it's the wiring harness being corroded or chewed by a rodent near the rear subframe. I've also had lads spend a fortune on sensors when the real culprit was a tiny, whistling pinhole in the exhaust weld just before the sensor, confusing the readings.
What a UK garage should charge for P0142
You're looking at £50 to £80 for a decent diagnostic plug-in and live data check. If it is the sensor, a quality Denso or NGK unit will cost you between £70 and £140 depending on the lead length. Labour is usually an hour (£60-£100), but that doubles if the sensor is rusted into the pipe and needs the oxy-acetylene torches out. A main dealer will easily quote you £450+ for the exact same job using the same brand of sensor in a different box.
P0142 repair cost in the UK
Most P0142 repairs land between £90–£320 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 P0142
If you're taking this to a garage, don't just ask them to 'change the sensor'. Insist they do a 'continuity and load test' on the heater circuit first. These sensors are a nightmare to get out—often seizing solid in the pipe—so if they snap it or strip the threads, you're looking at a new exhaust section too. Ask them to use a proper inductive heater to get it out rather than just reefing on it with a breaker bar. And for heaven's sake, don't buy a £20 'universal' sensor off eBay; they never work on modern Euro 5 or 6 looms.
Can you drive with P0142?
Yes.
Urgency: medium.