Officially? A wall of jargon. To most people? Absolutely nothing. That's exactly why we built the app.
Plug into any code reader and you'll get the same line every other app shows you. Technically correct. Practically useless.
"The rear oxygen sensor — after the catalytic converter, bank 1 — is reporting a voltage that's stuck high, which in O2-sensor language means 'rich'. Two very different stories can put it there, and telling them apart is the whole job. Either the sensor circuit itself is faulty — a short, chafed wiring or a contaminated sensor pinning the signal high — or the sensor is honest and the engine really is running so rich that raw fuel is getting past the cat. Check for fuel-system codes and look at your trims first: if the engine's genuinely rich, a new rear sensor fixes nothing."
Worth checking in roughly this order. Don't jump straight to the expensive fix:
The code itself is a snapshot. The fault sets after the car's watched the numbers over a whole drive cycle. Here's what's worth keeping an eye on:
Illustrative panels. These readings aren’t in our free demo drive, but the app shows them live from your own car.
Codes rarely tell the whole story. The clever part is reading them together, and against your exact car. Here's the kind of thing it catches:
The rear oxygen sensor — after the catalytic converter, bank 1 — is reporting a voltage that's stuck high, which in O2-sensor language means 'rich'. Two very different stories can put it there, and telling them apart is the whole job. Either the sensor circuit itself is faulty — a short, chafed wiring or a contaminated sensor pinning the signal high — or the sensor is honest and the engine really is running so rich that raw fuel is getting past the cat. Check for fuel-system codes and look at your trims first: if the engine's genuinely rich, a new rear sensor fixes nothing.
Yes. If it's just the rear sensor or its wiring, the engine runs normally — same as P0141, it's a monitor, not a controller. The caveat: if the engine genuinely is running rich, that wastes fuel and slowly cooks the cat, so don't sit on it for months without at least checking the trims.
A rear sensor is £30-100 plus fitting, and a wiring or connector repair can be nearly free. But hold off buying until you've checked the trims — if the real fault is a rich-running engine (say a leaking injector), that's a different bill and the new sensor would've been wasted money.
Not with the engine light on — automatic fail since 2018. And if the underlying cause is genuine rich running, the emissions test is at risk too. Diagnose which story you're in first; then it's usually a cheap fix either way.
Free app. Plug in, and get every code in plain English, plus the connections you'd never spot.