Insignia B: Fault codes P11DC / P2A02....MPG question

[FUG1]

Hi Gang,

Got an issue with the NOX2 Sensor, but also may have a problem with the fuel injectors, hence two codes are showing when we investigated this (P11DC / P2A02). Spoke with a bloke at Vauxhall who said there would be no issues to the car if I simply kept driving and didn't bother to have the sensor replaced until the next MOT (Jan'25),so I'll probably do this unless someone on the forum thinks I shouldn't?

I also think there may be another issue as my MPG is down by about 4-5MPG; I've tried running injector cleaner through the tank, but MPG still stays lower than I'd expect. Car seems to be running just fine, so any advice would be gratefully received ??

Thanks in advance

[Hindle1976]

Change the nox sensor, I had mine done under warranty no problems since, as for mpg sounds like it needs a long run to set it all back up or disconnect the battery for around 40 mins and let the onboard computer reset itself, how long u had it?


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[lizzard-t]

Poor mog is a by product of a failing NOX sensor
as you can understand the sensor measures the amount of nitrous oxide but also it’s the amount of oxygen it sends the information back to the ecu .
which in turn will adjust the fuel air ratio.if the ecu is getting an erroneous signal from the NOX sensor it will try to adjust the fuel air ratio which will start upsetting your MPG .
also the NOX sensor has a built in high limit kind of stat with the increased fuel delivery so the temperature of the exhaust will go up as well .
so if Vauxhall say it’s ok to get it replaced when mot due then get that in writing from them ,Because I don’t think so myself.

[Hindle1976]

Poor mog is a by product of a failing NOX sensor
as you can understand the sensor measures the amount of nitrous oxide but also it’s the amount of oxygen it sends the information back to the ecu .
which in turn will adjust the fuel air ratio.if the ecu is getting an erroneous signal from the NOX sensor it will try to adjust the fuel air ratio which will start upsetting your MPG .
also the NOX sensor has a built in high limit kind of stat with the increased fuel delivery so the temperature of the exhaust will go up as well .
so if Vauxhall say it’s ok to get it replaced when mot due then get that in writing from them ,Because I don’t think so myself.

My mpg was unaffected when my nox sensor screwed up that's why I suggested resetting the trip computer so it learns the driving style again, here's a gud one, I asked the dealer out of curiosity how much the sensor cost them and I got told little under £800 for it from Vauxhall, surely that can't be right can it? FUG1 I'd get it replaced asap screw what they said about it keeping till it's new mot the eml is lit to tell u there's a problem, don't ignore it the problem could only get worse, google the sensor and u should be able to get an oem one at a reasonable price, they're an absolute doddle to fit but u need it up in the air lizzard-t what’s mog? Lmfao


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[FUG1]

Magic! Thanks Lads, I'll get this done; when I spoke to Vauxhall the part was something like £800.00, and then they also wanted £189.00 to put it through the diagnostics test...ugg!

I've seen Drew replaced his on an earlier forum query, so I'll look to do this (as you say Hindle1976, it doesn't look difficult).

Thanks again!

[FUG1]

PS. we reset the computer, but MPG still down (fault light reappeared after a few days).

Cheers

[Hindle1976]

Just be careful not to burn urself if ur engine has been running, if u got a code reader don't forget to clear the fault when you've done the job, I hear neo brothers are reasonably priced for things like that


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[FUG1]

Just be careful not to burn urself if ur engine has been running, if u got a code reader don't forget to clear the fault when you've done the job, I hear neo brothers are reasonably priced for things like that


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Thanks, I'll check that out as I've been using my brothers's code reader.

[Hindle1976]

Thanks, I'll check that out as I've been using my brothers's code reader.

What reader does he have? Look up think diag on here there's a post somewhere giving members a discount 20% I think it is, I'm not sure tho


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[Drew]

PS. we reset the computer, but MPG still down (fault light reappeared after a few days).

Cheers

To be honest I have convinced myself that my mpg is down about 5mpg and I am looking for a reason. To be fair my driving has changed a bit, fewer miles and fewer long runs. My stop start stopped for a while and I though sh!t there's something wrong, but is working as it should again, possibly because the car had been sat a while. I have had no emls and it all scans fine. I have had the map out and cleaned, it only had a light covering of soot and I have dosed it twice with injector cleaner. I will probably look at egr and swirl flap actuator next to make sure they are functioning properly. When I had the cam chain done at Franks he said the egr etc. looked good.
The car drives beautiful though so it may be just a change in my driving habits?

[FUG1]

To be honest I have convinced myself that my mpg is down about 5mpg and I am looking for a reason. To be fair my driving has changed a bit, fewer miles and fewer long runs. My stop start stopped for a while and I though sh!t there's something wrong, but is working as it should again, possibly because the car had been sat a while. I have had no emls and it all scans fine. I have had the map out and cleaned, it only had a light covering of soot and I have dosed it twice with injector cleaner. I will probably look at egr and swirl flap actuator next to make sure they are functioning properly. When I had the cam chain done at Franks he said the egr etc. looked good.
The car drives beautiful though so it may be just a change in my driving habits?

That's interesting, Drew. Mine's definitely down (4 - 5mpg) since the fault started showing, so I'll look to get the NOX2 sensor replaced. Normally, I would expect an average of 44MPG (mixed A roads / Dual-Carriageways). When have you needed to clean the MAP sensor before??

[Hindle1976]

What's ur actual mpg? Out of curiosity


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[FUG1]

I'd expect in Winter to be getting at least 41mpg (we live on a quiet lane, so I usually leave her warming up for 5mins if it's really cold, which doesn't help my mpg!), but since the NOX2 sensor issue this has dropped to 36-37mpg. In summer I'd be getting 43-44mpg.
The best mpg I've ever achieved was on a trip to Wales and also a Devon trip where we got 49mpg (and I don't hang around on the motorway, either!).

[Hindle1976]

What model is it, mines the Sri grand sport vx line nav, I'm trying to find out what others are getting out of theirs so I can compare, and maybe change my style of driving if needed because I have no idea what I should be getting out of it


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[lizzard-t]

MAP sensor should be part of regular maintenance it's easy and doesn't take long just to whip it out and give that all important clean .
i took mine out yesterday out of curiosity,Because I haven't done it in 7 months,and it was as clean as a whistle.
and that's with stop start driving and using Tescos bog standard diesel .