E46 Fanatics Forum banner

Limp mode from MAF

43K views 170 replies 14 participants last post by  Chill Deluxe 
#1 ·
My car always goes into limp mode after a few seconds of movement, not just when idling however. When I unplug the MAF sensor the limp mode never returns. I got a new MAF sensor from VDO with no improvement. Any thoughts?

Sent from my DROID RAZR MAXX
 
#2 ·
I should say it takes about 20 seconds for it to jump into limp mode, and never does at idle with MAF plugged in. When unplugged, car starts rough (as it always does with no MAF) but never gets a limp mode error, just an SES.

Sent from my DROID RAZR MAXX
 
#3 ·
Anybody? My problem has slowly crept up to being worse and worse. I got limp mode once a month when I first bought it, and a restart would solve my issue. Now its gotten to he every start. Dealership isn't opened on the weekend, so I'll get generic Autozone codes pulled today. I'm thinking DME..

Sent from my DROID RAZR MAXX
 
#4 ·
Immediate thought is that it wasn't even/solely a MAF problem in the first place. Otherwise the new MAF would have fixed it. Right? Possibly something downstream of the MAF. Intake camshaft sensor? What made you think MAF? You got no fault codes? You need fault codes. You can't really just guess these things. They are all inter related.
 
#5 ·
What made me think mass air flow sensor was that when it is unplugged it fixes the problem. No more limp mode. However now my ECU will not connect with any type of scanner tool.. I had the same guy at autozone do it for me and I did it myself and neither of us could get it to work any longer. Its most likely not the wiring harness because it doesn't happen from bumps. Either way I cannot scan my codes now so I need to figure out what is wrong..

Sent from my DROID RAZR MAXX
 
#6 ·
I haven't been able to pull fault codes for some time now. I guessed MAF sensor because it didn't go into limp mode when it was unplugged. Likely assumption if you can't get codes.. before frequent limp mode I could pull codes. I have replaced the ICV (I had a p1500 code) and the MAF. All intake boots are good, TB plate moves well, although has resistance on it, but never gets caught up or stuck. I assumed this was normal.

So, something that puts you in limp mode AND stops you from pulling diagnostic codes. I'm thinking ECU... DME problem?

Sent from my DROID RAZR MAXX
 
#11 ·
No Actron scanners will work. I can't get an appointment with the dealership that actually works around my schedule.. are there no other shops other than dealerships that can read specific codes?
Are there any Indy shops that can simply clear adaptations for me, you think?

Sent from my DROID RAZR MAXX
 
#12 ·
You show your car as a 2001, however, you probably have a large round connector under the hood, if you do, you will need the round to standard ODB adapter cable to read your codes while connected under the hood.

Also check the terminals in the MAF connector and make sure they are not damaged and are tight.

If you have a CEL on, get your codes read and post back here for comment. Check to see if you have the large round under hood connector as well.
 

Attachments

#13 ·
My vehicle was produced post-OBD II change, it only has the 16 pin under the dash. The codes cannot be pulled, I don't know why.. pin 16 has power but it does not connect. I've fiddled around with the key a lot to no avail. I now realize that it takes a minute to go into limp mode because the car starts on an open loop system, not utilizing most of the sensors. Once they are in spec with where they should be, the ECU turns to closed loop, and begins using these sensors. That must be where the limp mode comes from, as when the MAF is unplugged, it is in an open loop the entire time, not just partially. One of the sensors must be off, or my DME is jacked up (which would explain the OBD II mess-up). The only thing is, the ICV and MAF are new, the TP sensors would make it go into limp mode even when in open loop, as would the wheel sensors, and I don't know what other sensors are activated only in closed loop.

Does anyone have a list of closed-loop only sensors? That would be wonderful. If the CSP sensors are included, specifically the exhaust side, then I know where I'll start. That one leaks oil and the o-ring has been replaced (unless the oil is from the nearby VANOS unit, and I'm looking at it wrong).

Sent from my DROID RAZR MAXX
 
#15 · (Edited)
Weste46,

I don't think your problem is from a BAD MAF. Unplugging the MAF just default the engine to run on its pre-determined fuel/air maps. When the MAF is plugged in, your DME/ECU is using realtime data (air flow) to calculate the fuel/air mixture.
This is the reason why your car doesn't go into limp mode with the MAF unplugged.

VDO/Siemen is the OE supplier to BMW for its MAF. Therefore, the likley hood that your new MAF is also defective is unlikely.

Like everyone said, just get a diagnostic because solving this complex problem will be difficult w/o a scanning tool. BTW..autozone offer free SES/CEL scanner assuming you have an OBD-2 port and not the older BMW DLA port (cicular plug located in the engine bay)

I hope this helps, good luck!!
 
#16 ·
I think my posts might be too long, but most of you are not reading them thoroughly. I realize the open loop ECU mapping is the reason for the limp mode not appearing. I also believe the MAF is fine. My problem now is finding out WHICH sensor or wiring harness section is defective, but I can't figure it out because of my MAIN problem, which is absolutely NO connection to my OBD system.

Sent from my DROID RAZR MAXX
 
#17 ·
Update: still not wanting to spend all that money to have it scanned, but have noticed something new. When in limp mode, MAF connected of course, I get a rough idle. Never when in open loop. So, it has to be a sensor that is not used in open loop, that would give a SLIGHT bouncing idle. It gets worse and worse subtly when I do notice the idle is bouncing.

Someone? It can't be that expensive to fix, so I don't want to spend 100 bucks scanning it, when the sensor will most likely cost less than that to replace.

Sent from my DROID RAZR MAXX
 
#18 ·
Have you given any thought to the idea that the main computer is toast?

Your car runs poorly, it MUST BE THROWING CODES. It has to be. If you cannot pull codes, then at least one of them is that the computer doesn't work, and if there is no computer then the car should be expected to run like crap.

Your car is a 2001, so it will talk to through the Data Link Connector to a pc running the diagnostic software. Your car _should_ communicate through the OBD II data port in the left side footwell, but you have said that it does not. You confuse me on this point though, you said it powers the scan tool, but then you said you can't find 12V. I'm confused at how the scan tool can be powered without 12V. You MUST set the ignition to RUN (Position II) to get codes out.
 
#19 ·
A MAF sensor costs more than the scan.

The MAF should not invoke Limp Mode. I suppose it could, but I cannot form the logic in my head to support such a thing. A MAF is not a required part for simple engine operations. It is required for complex engine operations, and the complex operations would be needed to conform to emissions requirtements. The MAF reports the air density, and the information is used to modulate the fuel so that the proper air/fuel ratio of 14.7:1 is acheived and maintained. The O2 Sensors are used to fine tune the fuel mixture, and the inability of the O2s to fine tune the mixture is reported as RICH, LEAN, or MALFUNCTION. There are codes (FUEL TRIM and FUEL CONTROL, the latter being BMW codes in the P1 family) for these conditions. My car had a bad MAF, but it did not invoke Limp Mode. Indeed, my car had a bad MAF, and were it not for a host of other codes that appeared repeatedly, I would not have known there was anything wrong with the car. It ran perfectly, except that the Check Engi8ne light kept coming on.
 
#20 ·
The codes CAN be pulled now, I fixed that issue, sorry for not saying that. The only code that appears is a P1500, which is ICV stuck open. the ICV is new however. The MAF has been replaced, and I know is not the problem, im not sure how to change the title of the thread.. it's not the ICV or MAF, but seems to have to do with both, and is NOT used while in open loop mode.

Thanks!

Sent from my DROID RAZR MAXX
 
#22 · (Edited)
ICV stuck open is a problem that can give the symptom you describe.

Your car is able to tell you where it hurts, you have to look at the stuff it thinks is wrong before you start to build a list of other things. If the ICV is new, then you have to figure out if it works, or if the connection is jacked, or whatever. The car THINKS the ICV does not work, and you have to make it know that the ICV does work.
 
#21 · (Edited)
Buy the BMW Scan tool from Xcar360.com and try to read it. If you can't, well then at least you have it to use in the future. If that thing can't read it, then your computer is gone. You'll have to buy a new unused DME.

EDIT: Saw your reply while I posted...


The ICV may be new, but if that's the code it's giving you, check to make sure it was installed correctly. I mean take it off and reinstall it properly after inspecting it for damage. I'm curious as to why you would ignore what the code tells you directly? The computer knows the position of the valve, so it knows if it's not moving anymore...
 
#23 ·
I have the BMW 1.4.0 Scanner, it does not pull codes even when soldered correctly, only programs for DRL, etc. The reason I thought the ICV was okay was because when the MAF is unplugged the car runs fine. I assumed if it were a bad ICV, it would give me problems with or without the MAF. I was hoping the P1500 was too generic of a code, and that it might not REALLY mean ICV stuck, but rather something relating to it. I can always try again, but it would have to be the connections.. I highly doubt this is the case however; bumps in the road never invoked the limp mode, it just happened more and more frequently until now, seeming to be a sensor malfunction. I will check into the ICV one more time (I've been in there 3 times now) and report back, though I have low hopes for the outcome.

Sent from my DROID RAZR MAXX
 
#25 ·
YOU NEED TO PULL CODES. Sheesh!

How do you know you have a P1500 today if you cannot pull codes TODAY to see why the Check Engine (SERVICE ENGINE SOON) light is on? Holy crap, you said you have a code, this means you have a scan tool that does the job of pulling codes.

What in your universe is Limp Mode? I know what limp mode is, but the stuff you are looking at should not invoke it. And if the car is in limp mode, then the Check Engine light should be on, and you should be using an OBD II scan tool to see why the light is on. YOU CANNOT ASSUME ANYTHING. Even if you know the code earlier was P1500, there is no way to know that the same code is coming up today.
 
#24 ·
You likely have a bad vacuum leak, which causes the DME to think the ICV is stuck open??

Vacuum leak could also cause MAF codes as well.

Check the simple stuff first.

See the first link below in my signature for ideas.
 
#26 ·
I cleared my codes a while back, plugged in everything and when it went into limp mode again I immediately turned it off and pulled the codes and received P1500. That is all. I appreciate your help but some of your not reading my full thread, or at least not clearly enough.

Sent from my DROID RAZR MAXX
 
#29 · (Edited)
Make sure you do not have a battery or charging problem.

See signature for Hidden OBC Menu and monitor battery/charging Voltage on the dash.

You would be surprised what may actually cause limp mode and multiple dash lights!
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top