True, but they said they checked everything and couldn't find a fault. If you check your temperature with a thermometer and it reads high you don't assume the thermometers broken. If the problem has persisted with a new sensor then the sensor isn't at fault and there must be a fault with the exhaust system/engine that they haven't identified. I would have thought replacing the sensor was a last resort once they've eliminated other possibilities. In any case if they come back with another potential fix that's going to cost more then I don't know whether to take it and risk the problem returning again.

Thanks for the response, it's a 2002 Vauxhall Corsa 1.2 litre, 3 door hatchback. It's only done 23,000 miles though so very soon for the part to fail. They replaced with a genuine part, I checked out the price with the Vauxhall dealership and they would have charged the same, maybe not the cheapest place I guess. Google seems to say that the lambdas often give a faulty reading if the manifold is rusty (grounding problems) or there is a leak in the system so I would assume they checked that. If they ring up and say they've found the problem i'm tempted to argue that they should have discovered that in the first place instead of just assuming sensor fault, so laziness on their part. Do you think that would gel? Many thanks for your responses.

Hi, I put my car into a garage run by Service4Service so that they could check out an engine warning light. They said that they found nothing wrong with the engine so just reset the system and returned the car, however the warning light came back on on the next drive so I took it back in. They said that the fault signal came from the lambda sensor in the exhaust, and because there was nothing wrong with the engine the sensor must need replacing. I agreed the work and price, which was reasonable at £192. However on the next motorway drive the warning light has reappeared so it seems the sensor isn't the problem and there must be an underlying issue. Am I within my rights to try and reclaim the money they took for replacing the sensor when it appears that the original was working perfectly well and they haven't solved the underlying problem? I am taking the car back to the garage so what should my stance be on resolving the issue? Thanks, David