[Boland01]

had been getting misfires on Cylinder 1 and 2. Changed the spark plugs, coils and even injectors (index 12) with no change. I also replaced both front oxygen sensors. With that the car is still running terrible with the half engine light.

We measured the oxygen sensors with the torque app and bank one sensor one is giving no reading - flat line. I tried switching oxygen sensor connections at the engine and no matter what I do bank one has no signal just a flat line. Switching bank two connector at the engine with either bank one or two oxygen sensors will give us readings.

This tells me now the fault is either at the bank one connector on the engine manifold or somewhere behind it. Could be the sensor wiring to the ECU. Has anyone seen this issue before? Any ideas? It's a 2007 335i. I can't find anything on the internet so far. I've scheduled an appointment with BMW on Monday and my indy was afraid to tackle it.

[techwhiz]

O2 Connector under cover to DME wiring is bad somewhere.

[BashShah]

Originally Posted by techwhiz

O2 Connector under cover to DME wiring is bad somewhere.

Or DME is Bad.
I just went through this.

The Wires for both of my o2 sensors were melted cause I over heated my car.
10 inches wire near exhaust melted causing a short in wiring.
Some other plastic also melted but not something vital.
It was extremely cold when this happens so the cold was helping my situation.

Ok, you stated:
We measured the oxygen sensors with the torque app and bank one sensor one is giving no reading - flat line. I tried switching oxygen sensor connections at the engine and no matter what I do bank one has no signal just a flat line. Switching bank two connector at the engine with either bank one or two oxygen sensors will give us readings.

Before my solution, I highly recommend a diagnostic with a Proper BMW tool like INPA or ISTA

So you have a short in 1 of 2 places.
1) in the wiring from Dme to O2 connectors on top of the Engine.
2) in the DME.

The proper diagnostic:
And this can only be done at a reputable BMW Dealership......I don't think any INDY shop has this equipment.

You need to get a 1 hour diagnostic, and before handing key to dealership, you need to speak directly to shop foreman and advise him of your diagnostic, and parts replacement.
And ask them to unplug DME and install their diagnostic harness and test values from both Bank 1 and Bank 2.

If you want to do a continuity test yourself on the wiring, it won't help.
Cause there are 5 wires from each sensor to connector on top of engine, and there are 6 wires from each plug on top of engine to Dme for each sensor.
And to make things worse..... out of the 6 wires approx 3 of the wires end any where from 3 to 8 different locations on Dme harness alone.
I already did this....

So for me it was the DME and dealer wanted to replace it for 2200 Canadian and 5 hours programming.
I got it done for $325.....LOL
Good luck.
I got it done for

[Boland01]

Thanks for the replies, hopefully just a loose connector. Taking it into the dealership tomorrow.

[Manic Mechanic]

Hey Boland I'm in Magnolia also with a 535i so I'm curious about repairs around here. Did the dealership take care of this? What was the problem. Who's your Indy out here?

Thanks,
Vernon

[Boland01]

Originally, I took it the car to Magnolia Auto Specialist. They are great. Unfortunately, they couldn't pin point the cause. Didn't even charge me though.

I ended up taking the car (barely) to BMW of the Woodlands. Turns out my DME was fried. Just under $3K later it seems to be back to normal. At least they put in an updated MDS81 DME rather than the original MDS80 the car came with.

[B@man335]

Originally Posted by Boland01

Originally, I took it the car to Magnolia Auto Specialist. They are great. Unfortunately, they couldn't pin point the cause. Didn't even charge me though.

I ended up taking the car (barely) to BMW of the Woodlands. Turns out my DME was fried. Just under $3K later it seems to be back to normal. At least they put in an updated MDS81 DME rather than the original MDS80 the car came with.

Out of curiosity, what symptoms were you experiencing? Fault codes? I might be having same issues

[Boland01]

Misfires Cyl 1 and 2. Then randomly jumped to 4. No signal to Cylinder 1 and 2. Lamba probes on the two front banks.
I replaced coils, spark plugs, new index 12 injectors and front oxygen sensors. Previously had the mosfets done.

At first it would misfire bad then run normal like nothing happened. It progressively did it more often. In the end it would misfire on 1 or 2 cylinder constantly.

There are people that could have supposedly fixed the DME but I already had the mosfets done and had thrown over a grand in parts at the car with no results plus Magnolia Auto Specialist who is good was afraid to tackle it. In the end, I gave up and bit the bullet. Or I guess it bit me for $3K. At least I now have the updated MDS81 DME and a two year warranty on it.

[Manic Mechanic]

Thanks for the reply, I know Jeremy and crew at Magnolia Auto Specialist and they are good, not as good as me but not a bad choice in any case. They don't like to get bogged down but rather keep the normal stuff in high gear, for instance they have refereed engine jobs to me.
I have never sent anything like your issue to a dealer, only what I can not do because of special tools or programming equipment. I'm the local guy who fixes the hard ones. I still run the normal stuff through but that's why I have four men in the shop who allow me to spend more time on the difficult ones.
$3K for a module replace is a kick in the back side, to me at least, it's good that you have an upgrade and a 2 year warranty as you said. I've been thinking of taking mine in to them for a complete software update and NAV map update before I go any further. I'm pretty sure my wastegates are in need of adjustment.
I'm about 3 months into owning my N54 car, I've done a bit of maintenance work and acquired a moderate war chest of bolt on performance parts to get ready for higher boost. So far my car has been a jewel and just what I wanted. I'm learning the specifics of this platform and trying to find a long weekend to take it down for upgrades when the rest of my fleet is not in need if you know what I mean.
Perhaps we'll meet up some time, or if specialists is afraid again give me a ring and I'll be glad to see what I can do for you. I'm just in town across from Auto-Zone at Magnolia Auto, that's my full service auto shop.

Vernon

[Boland01]

Thanks Vernon. Enjoy your 535. I'm running a JB4 on Map 5 with DCI's so my 535i is pretty mild. Compared to the two 335i sport coupes they are completely different cars. For comfort and room the 5 series all day. For sportiness and fun the 335i. One of them is a manual transmission so with light traffic that's my favorite.

[jordan.hashem@gmail.com]

Originally Posted by BashShah

Or DME is Bad.
I just went through this.

The Wires for both of my o2 sensors were melted cause I over heated my car.
10 inches wire near exhaust melted causing a short in wiring.
Some other plastic also melted but not something vital.
It was extremely cold when this happens so the cold was helping my situation.

Ok, you stated:
We measured the oxygen sensors with the torque app and bank one sensor one is giving no reading - flat line. I tried switching oxygen sensor connections at the engine and no matter what I do bank one has no signal just a flat line. Switching bank two connector at the engine with either bank one or two oxygen sensors will give us readings.

Before my solution, I highly recommend a diagnostic with a Proper BMW tool like INPA or ISTA

So you have a short in 1 of 2 places.
1) in the wiring from Dme to O2 connectors on top of the Engine.
2) in the DME.

The proper diagnostic:
And this can only be done at a reputable BMW Dealership......I don't think any INDY shop has this equipment.

You need to get a 1 hour diagnostic, and before handing key to dealership, you need to speak directly to shop foreman and advise him of your diagnostic, and parts replacement.
And ask them to unplug DME and install their diagnostic harness and test values from both Bank 1 and Bank 2.

If you want to do a continuity test yourself on the wiring, it won't help.
Cause there are 5 wires from each sensor to connector on top of engine, and there are 6 wires from each plug on top of engine to Dme for each sensor.
And to make things worse..... out of the 6 wires approx 3 of the wires end any where from 3 to 8 different locations on Dme harness alone.
I already did this....

So for me it was the DME and dealer wanted to replace it for 2200 Canadian and 5 hours programming.
I got it done for $325.....LOL
Good luck.
I got it done for

Hey there, I'm having a similar problem except 3 out of 4 sensors are reporting fine. But you've been the most detailed and knowledgable about the routing from each sensor to the DME. I'm trying to run a connection from B2S1 to the DME. I thought about buying a used harness to do that because the wires are equal in length. Only thing is, I only want to extract the wires for just B2S1 O2 sensor to the DME and reroute under the hood without shortening it or running it under the engine. Then I guess begins the game of pinning it into the plug for the DME after removing the old one.

1. are the wires braided all the way to the DME's plug?
2. how hard will it be to remove the old plugs from the DME's plug and replace them with the replacement ones for the B2S1 plugs?
3. Is there any other solution for my situation to get around having to replace the entire engine harness?

I know it's been a while since you posted about this, but it doesn't hurt to ask. Thank you!