HELP!!! BMW 535i problems
 

its my sons car. he bought it with some problems.
it had a bunch of codes and would only run in limp mode.
not sure of year but it is the N55 engine.
with as many codes that it had i was hoping something was loading the DME down.

we did fix some of the codes.
it was the valve tronic motor for the cam lift timing.

the codes come up as soon as your turn the car to "on".
the codes left are
charge pressure sensor intake electrical short to earth
absolute pressure sensor electrical short to earth
rail pressure sensor electrical short to earth

not sure what this one is but i dont think it matters.
AUC sensor internal sensor fault. i think it has something to do with heat/ac

what we have done:
he has replaced all the sensors that have codes with BWM sensors.
we checked the wiring. nothing is shorted.
he sent the DME off to be tested/repaired and it was good.
battery is new, it is also on a charger
he also replaced that (dont remember what its called) electrical "box" that is connected directly to the battery.
and yes we can clear all the codes.

here is the thing.
if you unplug the sensors you get the SAME "electrical short to earth " fault.
so we think for some reason the DME is not "seeing" the sensors.

i have been thinking about voltage. as in the reference voltage that some sensors use. maybe its wrong or missing.
not sure why though as that "should" come from the DME and that tested good.
is there anything common between these sensors???

As complex as that electrical system is...I am probably the least qualified to comment but the one common thread to the codes you listed is grounding. My WAG is there’s a ground lead somewhere that’s disrupted.

There is a problem likely in the harness being pinched, water intrusion, or similar. Somebody or something has been in there recently. Try to sit down with your son, ask when this all started. There has to be a connection to an event, storms, climate, etc where immediately there after the dashboard lit up.

I believe he said his son bought it that way (throwing codes).

My sons 335i had some codes similar to that. It was a crack in the plastic charge pipe. Most of the boost was escaping.

The codes are there as soon as you turn the key to ON. Egine is not running. Well it runs. But I told him to fix the codes that come on first.
Now even running it’s the same codes. So no new ones.

Yes. Grounds. He mentioned that but we don’t know where they all are.
I do think there is one on the rear of the engine.

Yes he has looked at the harnesses. They look good.
I even ohmed them out but I am going to do that again.

I really think the key is we get the same codes if the sensors are connected or not connected.


Going to take it to a friends shop maybe next week. Oh yes just hard to give up and I just don’t know the car that well but he does.

Him and his friends have been “hot rodding “ these cars
His friend had 800 hp. He said he was beating the hell cats in it.

I bought one with bad turbos to flip. I kind of want to keep it but I need the money back.

So the “short to earth” is a lower voltage limit fault

But I get it with it connected or not connected.

There is a ground wire in the connector

If it is helpful , I can maybe get you a wiring diagram . I have found circuit codes to be fairly accurate . You either have voltage shorted to ground somewhere, like Asphalt suggested, or you have a component shorted out inernally.
Id pull up a wiring diagram, and start looking at the b+ circuits to the affected sensors, the circuits back to the ecm, and Id also look for that AUC sensor ?? unplug it and see if your circuit codes go away .
Your best move, is to lift off the plastic engine cover, and hold it about 4 feet off the ground . Pull a Honda Accord under that cover, and then discard the 535. Problem solved .
I can help with a diagram if you need .

Good point about the the AUC. I have suggested from the begging that I thought there might be one bad sensor loading down the DME.
Let me have him pull the AUC first.
He also has a code for a door handle current.

2013 BMW 135is HVAC Gaseous Pollutant Sensor

Only for cars with automatic A/C.

Also suggest starting with the lowest (numerically) codes first, address one-by-one.

SUCCESS

So today after he tried some other things I said I know someone that can send me wiring diagrams
He says. I have all the wiring diagrams and more
WELL SON OF BISCUIT !!!!!!
I check the 5v on two sensors and it’s good.
The ground wire is good.
So then I ohm out the “signal” wire and it’s open.
What’s more is that I am getting different readings when checked to all the different pins.
There is an “extension” cable plugged in between the wiring harness and the DME.
so I remove that and the wire is good up to that point.
Now I think the “extension” harness is bad.
He looks up the part number on it and it is a DINNON part. !!!
There is some dinnon module added , not sure if it is factory, that bumps up the HP.
He says the three sensors we have problems with all go through this dinnon module.

We remove the “extension “ harness and connect everything back up and all is good.

Thanks for all the suggestions and help.

BTW. the software he has on his computer is amazing. So much info about the car and each part.

Now gotta get my turbos on.

Nice- two ways to “tune” the ecu in these cars- piggy back as you found or flash the existing ecu. If you plan on running higher boost, invest in upgraded charge pipe (like elephant) and recirc valve (like Forge). Lots of plastic in engine bay including valve cover. It all cracks over time.

that program he has is amazing.
it shows you where the part is on the car
tells you what it does
just tons of info.
great wiring diagram
but with these cars you need it.

What’s the program? Is it available for other BMWs?

Yes please as I'm having an issue on my '08 528xi tpms antenna module, it's not communicating. I believe there is an open in one of the 3 circuits from the ABS unit to the module, but just haven't had time or wire diagram/ source to look into it further .

hey jim. come to find out he has the diagrams to the 330 also!!!! when he said that i thought about your fan problem.

Paper or digital? Also, does he have software to diagnose the problem?

I used INPA and the fan work correctly. the 50 amp fuse is good and sends power all the way to the fan. I check the PMW(?) Wire and had continuity from the DME all the way to the plug. I swapped and a new fan but it was a no go.

Right now I have it on a relay with a switch in the cabin. Hopefully this weekend, I can hook up an adjustable thermal sensor to turn on the fan automatically.

digital
said it is like 70g on his computer. thats pretty big.

he may be able to print it

He could be talking about Dinan. Reputable BMW tuning shop out of Mountain View, Bay Area, California.