FSI O2 Sensor No Start

kujiwara

Member
Need help identifying an issue with the car, took the car to an MOT center and failed emissions, they tried replacing the O2 sensor and then car would not start (I think they wired it wrong). They tried putting in the old sensor and still wouldn't start. Car does crank. Does the FSI wiring system have any fuses protecting the ECU from being damaged by this? The car's been sitting there for two days already and they haven't made progress? Any idea what could be causing this? I believe the O2 sensor is the only thing they touched. I've found spare ECU and immo delete service already, but the shop seems hesitant to jump to that cuz they have to cover the costs.
 
I saw this when you first posted it in your main thread last night and I very much sympathise. However, I wasn't surprised by the lack of comments offering potential diagnoses, since the first port of call with any FSI is to run a VCDS scan.

Unfortunately I doubt that your "MOT center" has anything approaching the level of expertise required to get this sorted, and you may well need to identify a relatively local specialist, and then get the car moved there.

I'm sorry that I'm sounding so negative and unhelpful. Hopefully others will chip in with more practical suggestions pretty soon.
 
Definitely need to run a scan, I cannot imagine replacing the O2 sensor has caused issues as it would just be 2-3 contacts going to the sensor with a plug of some description.

Does it crank and not start or does not even try? might have shorted a fuse out or something but I can't think of anything you'd touch to do that under the car.

as Steve_c said, need to do a scan for a better idea as it is not enough to work with for a good guess.
 
Definitely need to run a scan, I cannot imagine replacing the O2 sensor has caused issues as it would just be 2-3 contacts going to the sensor with a plug of some description.

Does it crank and not start or does not even try? might have shorted a fuse out or something but I can't think of anything you'd touch to do that under the car.

as Steve_c said, need to do a scan for a better idea as it is not enough to work with for a good guess.
I'm going in to run a scan today, they tried wiring in one of those universal sensors and car would not start after, even tried putting the original in and car doesn't run. When I google this scenario, it's common to see ecu being fried by it. Does crank.
 
Shop and I couldn't connect to VCDS so pretty sure ECU is fried? Gonna facilitate to a replacement ECU or repairing the old one depending on whichever is quicker, good thing is they will be responsible of the cost.
 
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