[stickle1212]

Hello all... still trying to understand the logging software. However, I now have a code for o2 sensor: Bank 2 sensor 2.

P0056
P0158

It may be completely unrelated to the initial issue.

[nsjames]

have you gotten INPA working?
If so, pull the DME codes with that.
Those P codes are pretty generic OBD codes.
The actual BMW codes are much more concise.

those particular p codes seem to be for a heated oxygen sensor fault, which jives with a shorted wire killing the DME. That's a high current circuit.
and then a high voltage o2 sensor reading, which may obviously be related to a short from the heat circuit.

anyway, i'd investigate the o2 sensors and related wiring heavily and get inpa up and working to get the factory diagnostic codes.

[stickle1212]

nsjames https://docs.google.com/document/d/1...it?usp=sharing

[Tambohamilton]

Originally Posted by stickle1212

nsjames https://docs.google.com/document/d/1...it?usp=sharing

Where are the O2 codes there?

[nsjames]

those both relate to the post cat bank 2 sensor.

check all of this stuff over, including the wires up top that go to those connectors on the back of the valve cover.

if it all looks OK, try unplugging the bank 2 sensor.
it should be 62202 in the photos.

the a731 jbbf code is, I believe, a problem with the 30F relay.
there's a few different junction boxs you could have based on build date.
what's your car's build date?
but that's also a suspect for "car seemingly shuts off" problems.

[Tambohamilton]

I'm not so sure the 30f relay could cause it to shut off...but regardless, it certainly isn't helping anything

[stickle1212]

nsjames 7/2007
The part that really bothers me is that if I moderately accelerate, I'm fine. Why would the electronics of the vehicle react differently to a rapid acceleration? and what component when disabled could cause such a rapid deceleration?

I have the 3 stage manifold setup. Could a malfunctioning disa valve cause this issue?

FYI, I replaced my transfer case this weekend and I still get that error about oil abrasion. (when I tried to do the recalibration procedure there was an error about communicating with the module)

[e90yyc]

Man I am SO curious to see what this ends up being…

I don’t see any possible way this could be DISA related.

I seem to have a permanent Oil Wear code on VTG, but I also have xDelete and I think this is byproduct of that.

Did you replace your TC just to rule that out? If so, damn. That’s a fair bit of work! Guess it’s done now though, haha…

I’m just getting hung up on the violent deceleration… Would an abrupt fuel cut really cause something as severe as what you’re feeling? This is a genuine question for anyone who might know.

In my case, when the car has a conniption there’s an abrupt feeling to how the throttle is cut, but I wouldn’t describe it as violent.

No doubt that troubleshooting something like this is above my level of knowledge, but I thought I’d try to chip in where I can.

[stickle1212]

e90yyc I've had my fuel pump go out on the highway while driving my e46 and there was never a rapid deceleration. I wonder what happens when there is an ignition power cut. I will replace the TC tomorrow (thankful for the junkyard). I'm also puzzled as to why It never happens in 1st or 2nd gear.

[Tambohamilton]

Whatever it is, it's an electrical/electronic fault; the tach going to 0 is proof of that.

Personally I think it's a wiring fault which manifests itself when the engine is pulling hard, somehow.

I'd start by chasing down the error codes you've got; they'll need to fixed some time regardless of whether they're the cause of your issues. May as well rule them out now.

[e90yyc]

Originally Posted by stickle1212

e90yyc I've had my fuel pump go out on the highway while driving my e46 and there was never a rapid deceleration. I wonder what happens when there is an ignition power cut. I will replace the TC tomorrow (thankful for the junkyard). I'm also puzzled as to why It never happens in 1st or 2nd gear.

Yeah, I know what you mean. The feeling of a fuel pump failing is nothing like what you’re experiencing.

It’s moments like these when I wish we had access to the same logging tools the N54/55 crowd has. If we do, someone please enlighten me because I haven’t had any luck with TestO.

But wait: You have replaced your transfer case or no? I thought a few posts back you mentioned you had done this. Are you replacing it a second time?

[eljay]

Originally Posted by stickle1212

e90yyc I've had my fuel pump go out on the highway while driving my e46 and there was never a rapid deceleration. I wonder what happens when there is an ignition power cut. I will replace the TC tomorrow (thankful for the junkyard). I'm also puzzled as to why It never happens in 1st or 2nd gear.

So, this never happens in 1st or 2nd gear?
I missed that before as my theory is that you have an exposed wire somewhere and with rapid acceleration, g-force moves it more than a gradual one and it touches something and shorts out and then rapid decceleration oves it away from touching and the normal electrical path resumes, which is why the cut is so brief.

I also noticed that everything else on your speedo stays on during the event except for the tacho. Even instant mpg gauge behaves normally it seems as it is meant to smooth out changes in mpg, so it's playing a bit of a catch-up to the throttle application.

[stickle1212]

e90yyc I replaced the fluid before but this past weekend I replaced the transfer case. eljay That's correct, never in 1st or 2nd which sometimes makes me think gearbox. @Tambohamilton, good point.

[stickle1212]

Tambohamilton Let's say it is a faulty circuit, which circuit/module could possibly cause such a behavior?

[Tambohamilton]

I don't know. Normally you'd see an error code(s) pointing to the fault. But I think whatever is happening here is abrupt enough that the DME doesn't have time to log the fault before it cuts out.

Like I say, I'd start with the fault codes you've got and fix them before worrying about much else

[stickle1212]

Is there a possibility that the gearbox could be the culprit?

[Tambohamilton]

Sure...I really don't know. But I doubt it. I've been wrong before, and I'll be wrong again soon enough...

But if you're referring to a mechanical fault, I really think that's highly unlikely.

[stickle1212]

My TC module seems like it was emersed in water but there are no visible signs of a breach. However, I took one from the Junkyard so I'll be swapping it tomorrow as well as checking the bad o2 sensor.

The problem happened today in a new way. I was very light on the gas and in second speed. I must say the bucking was just as severe as in the higher gears. I'm convinced this car Is possessed.

[stickle1212]

Originally Posted by nsjames

possibly.
also possible that something got damaged along the way.
it may be worth checking on the main chassis ground since it's in the vicinity. maybe it got disturbed and is a problem when the engine lays over under hard acceleration.
edit:
i'd have a look at the o2 sensor wiring too, a shorted o2 sensor on the manifold would drop the DME. just a general gander looking for damaged wiring at all the known spots.

I wouldn't think it's a kombi issue since the economy gauge keeps working and it doesn't appear to reset itself.

OP, speedo acts normal when the tach drops out?

it's gonna take some data logging to figure out what drops what.
in my opinion anyway. I'm not a professional.

this guy had similar symptoms and it was the dme, but it's a turbo car which i assume the OP doesn't have since it's got an econ gauge.
https://www.e90post.com/forums/showt...1445102&page=8
so not the same.

I'd be curious to see if OP loses communication with the DME at corresponding times with the bucking.

I was going over earlier posts....There is a significant decrease in speed when it occurs, it feels like it could cause a back injury. The rpm movement definitely reflects the feel of the car.

[stickle1212]

I replaced the o2 sensor and the CEL is now off but the original problem persists.
Replaced TC module (Oil wear code gone)

I get most of my parts at the junkyard so I've changed a few things in hope of striking gold.
eg: Transfercase, Injectors, TC module.
The only code remaining is (a731)

Observation:

Whenever the battery has been disconnected for an extended period, the vehicle is able to drive for at least 10-15 before the problem reoccurs (feels sluggish).

At this point, I'm a bit frustrated. I'm thinking about getting a clone DME and if that doesn't work, my friend wants to buy it for 3k as is.

[stickle1212]

Originally Posted by Tambohamilton

I don't know. Normally you'd see an error code(s) pointing to the fault. But I think whatever is happening here is abrupt enough that the DME doesn't have time to log the fault before it cuts out.

Like I say, I'd start with the fault codes you've got and fix them before worrying about much else

I've gotten rid of all the codes with the exception of:

A731 Bistable relay....
A554 SOS

[Tambohamilton]

Good work. A731 is one of the ones I'd be interested in regarding the issue to be honest... Hopefully sorting that yields some results