Hello. I don't know anything about cars, but I'm trying to learn a little about this problem. My engine management light intermittently lights up. Sometimes for a day, sometimes for weeks. It will go off, and stay off for a day, or weeks too. 

 

SO130 is the cause. Oxygen sensor I believe? 

 

My question is, where is this sensor. My mechanic says its deep in the engine and costly. Is this right. My MOT is due soon, and I do want to keep the car a bit longer despite its age. 

 

Please help if you can? 

That code refers to the Lambda sensor in the exhaust pipe before the catalytic converter, a new sensor (depending on what engine you have ?) will be around £70~120 and about an hour to change if done by a garage, might take longer if you're going to diy with the car on axles stands/ramps, but it might not be the sensor itself that has failed, it could be the wiring/connectors on the car that has corroded/failed not an uncommon problem

The engine is a 1.6 petrol, though its never ever lived up to that size and barely gets over 60mph! I get excellent fuel economy on long distance (up to 48mpg), but yesterday when I drove around 84 miles, the light came on, and I genuinely thought I was going to stop as it was stuttering etc. So glad yo get off the motorway! 

 

I'm guessing if it's wiring etc then it's expensive, and will that be buried in the engine? 

 

Thank you for your help. 

The sensor and the wiring is not buried in the engine, it's all external from the engine, and tbh if the connector from the sensor looks suspect a "getto" fix would be to replace the connector with a bunch of inline crimps and some protective covering over them, about a 30 min job

@Glennorm - Well, what Nige says is all correct, in particular the "oxygen sensor" is more commonly known as the lambda sensor, and is fairly clearly visible on the exhaust downpipe. Your performance is "pretty rubbish" for any Octy so something's not right.