CEL and P12BA code

A

ajguk

Member
Hi all

I had a check engine light a couple of weeks ago (2009 30i), no symptoms and a 'P' code (the number escapes me now unfortunately)....a spot of googling suggested the MAP sensor, which I changed, and the light went out. It's just come back on with a cold start and now my code reader gives a P12BA code...the only info I can find is someone else on here who fixed it with a MAP sensor change (which I've already done). How sensitive is the N52 to the MAP sensor brands? I went with a Delphi from Autodoc, perhaps I should try another? Or is there anything else this could point to? No discernible rough idle etc.

Thanks
 
MAP & MAF sensors are the usually culprit - did you just change out the MAP? (Delphi is a good brand BTW)

The code is thrown due to 'differential pressure sensor intake manifold plausibility trailing' - after those 2 most likely culprits, next most likely is the cylinder head valve cover.

You might get away with just removing that, cleaning, replacing. It has been known to be warped / cracked though - so you might need to replace once you inspect it.
 
Yes so far just the MAP. Funnily enough last year I had a CEL due to a leaking valvetronic gasket, I was close to replacing the cylinder head gasket, turned out to be a slightly easier fix (after making the initial mistake of using a non-oem gasket first, so the vacuum leak continued). Annoyingly I've just started her up again and cleared the code and it's gone, no CEL. RPM is bouncing around between 920-940, I'm not sure if that's normal but it actually does feel a little 'rougher' than usual. I guess the MAF sensor would be next then? If the cylinder head gasket needs replacing would there be some oil leakage like I saw with the valvetronic motor?

Ah just read your reply again - I take it the gasket may not be enough. It's the black top (plastic) cover I have if that helps. Cheers
 
Got it, thanks. Spotted some oil in the recesses between the coil packs, but I think this is some from before I changed the valvetronic gasket. I'll take it out for a few miles and see if I can spot any fresh, then will see what happens with the engine light (currently off with no codes).

If I end up doing the valve cover, would you recommend I get it from the dealer or is it an Autodoc job? Any brands in particular I should go for if so?
 
I would clean it first & see where you stand - it may not need replacing (50:50)

I don't have a recommendation on where to source the parts if you need to replace.
 
Great, sounds like a plan. It would be useful if BMW parts would answer the phone though so I could get a ballpark :D

Thanks for the advice, much appreciated. At least I've got a couple of things to go on now!
 
ajguk said:
Great, sounds like a plan. It would be useful if BMW parts would answer the phone though so I could get a ballpark :D

Thanks for the advice, much appreciated. At least I've got a couple of things to go on now!
Click to expand...
You can order here or use it to get prices. Just use RealOEM to get the part number the search. https://www.sytnerstevenagebmwparts.co.uk/
 
OK bit of an update.

I replaced the MAP sensor with a delphi unit, cleared the code, but it came back :(

I decided I didn't really have the energy to start messing around myself so took it to my Indy. They have replaced the MAP sensor (again) with an OEM unit, and the issue is still occurring. They have checked all wiring and plug connections, all are ok. Apparently ISTA says that after replacing the MAP sensor, the next solution is to replace the DME....at a cost of about £1600 inc. vat and fitting. :headbang:

Is there anything else I should try? Can I get a recon DME perhaps and have it coded? I was getting ready to sell her this year and not sure I've got the appetite to spend that, after just dropping £250 on it today only to be told it's not the sensor I already swapped!!
 
Pull the coil packs see if any have oil in the plug holes.
My car had one hole with oil in.

Symptom was unstable idle on start for 10 odd seconds.
But in trying to find a cure before i pulled plugs it was suggested out there to replace maf, which i did, no cure.
Also was suggested it was the engine blow back trap, molded on cam cover.

It was easier to replace whole cam cover, especially when i then found oil in plug hole 4.
New cam cover fitted, all cured.
 
flybobbie said:
Pull the coil packs see if any have oil in the plug holes.
My car had one hole with oil in.

Symptom was unstable idle on start for 10 odd seconds.
But in trying to find a cure before i pulled plugs it was suggested out there to replace maf, which i did, no cure.
Also was suggested it was the engine blow back trap, molded on cam cover.

It was easier to replace whole cam cover, especially when i then found oil in plug hole 4.
New cam cover fitted, all cured.
Click to expand...

Thing is there are zero symptoms, other than the CEL and the code. Last year I replaced the valvetronic gasket because it was leaking oil and a vacuum leak, where it would start, shudder then cut out. I think an oem valve cover is about £400 so perhaps that is worth a try - the garage has told me the DME "will not talk" to the ISTA so have suggested a replacement.

What cover did you use btw? Genuine BMW? I have heard good things about Elring which seem to be around the £180 mark.
 
Reamesy said:
Get a smoke tester and check for vacuum leaks.
Click to expand...

Thanks. When I replaced the valvetronic gasket last year I didn't have much success with a smoke tester, but maybe I should give that a try.
 
Cam cover about £120 odd from Autodoc.
Comes with seals and the valve.
https://www.autodoc.co.uk/spares-search?keyword=11127552281+Cylinder+head+cover
 
OK so finally getting round to (hopefully) sorting this. I'm going to buy the valve cover from Autodoc, seems like Elring are well respected, I'm trying to reduce the chances of doing it twice :)

Does this have everything I need or do I also need grommets I've read about elsewhere??

https://www.autodoc.co.uk/elring/16165416
 
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