Started this morning. Cut out momentarily while driving .....

2003 320i M54 2.3L SE Coupe. Doing 30mph in 4th behind a bus. Suddenly engine dies and recovers immediately. Stopped at lights. Idle fine. Started off again no problem. Pulled over at first opportunity to check codes. No codes. Spent the day in work. Coming home tonight same thing at about 35mph only more abrupt. The only difference is that this time the DSC, ADB and DBC lights came on and stayed on. This isn't a problem. All it means is that whatever happened turned the The Dynamic Stability Control, Automatic Differential Brake and Dynamic Brake Control (DBC) off and they stayed off. I can do that by pressing the button for 3 seconds. After that no problem with running or idling. Got home ok. Checked the codes and had a P0335 Crankshaft Position Sensor fault. So I guess I will be changing that on Saturday, if not before. Just thought I would run it by everyone for an opinion. Do the symptoms sound right for this fault? The thing is, I had both cam sensors and the crankshaft sensor replaced in June on a just-in-case basis. Could it really have packed up so soon?

How old are your fuel pump and fuel filter?

Before I would be jumping on the crank sensor, I would be checking the battery/charging Voltage.

You should be able to bring up the Hidden OBC Menu and be able to monitor you Voltage directly on the OBC display.

Crazy battery/charging Voltage can generate some strange faults and cause the dashboard to light up like a Christmas tree!

Would have never believed this until I witnessed it first hand.

Originally Posted by jfoj

Before I would be jumping on the crank sensor, I would be checking the battery/charging Voltage.

You should be able to bring up the Hidden OBC Menu and be able to monitor you Voltage directly on the OBC display.

Crazy battery/charging Voltage can generate some strange faults and cause the dashboard to light up like a Christmas tree!

Would have never believed this until I witnessed it first hand.

I would trust JFOJ on this one. He's been working on cars for more years than you've probably had hot meals! Or wait.. was that someone else?

Change battery, voltage regulator, fuel pump, fuel pump relay, and fuel filter and everything should be good to go for many years to come! PM FOR THE WIN!!

If the crank sensor is of unknown origin...that would be suspect just because aftermarket electronic things never seem to do well in our cars.

Those lights are pretty common, I think, and they indicate more than you think just because you can also 'manually' control them. If you search for them in a 'thread title search' I'm sure you'll find some useful threads.

I remember a few threads with cutting out while driving. It can just be loose cable on battery too, corrosion somewhere on one of the major grounds?

Originally Posted by jfoj

Before I would be jumping on the crank sensor, I would be checking the battery/charging Voltage.

You should be able to bring up the Hidden OBC Menu and be able to monitor you Voltage directly on the OBC display.

Crazy battery/charging Voltage can generate some strange faults and cause the dashboard to light up like a Christmas tree!

Would have never believed this until I witnessed it first hand.

Cheers. Will check that in the morning. You talk of strange faults. Would you list stalling like this amongst them?

Originally Posted by dmax

If the crank sensor is of unknown origin...that would be suspect just because aftermarket electronic things never seem to do well in our cars.

Those lights are pretty common, I think, and they indicate more than you think just because you can also 'manually' control them. If you search for them in a 'thread title search' I'm sure you'll find some useful threads.

I remember a few threads with cutting out while driving. It can just be loose cable on battery too, corrosion somewhere on one of the major grounds?

The crank sensor is after market so I will change it anyway. There are lots of examples of this on this and other forums but nothing in the way of conclusion.

Originally Posted by GSherbs

How old are your fuel pump and fuel filter?

Pump is 3 years old, or 30K miles so I doubt that has any issues. I'm thinking filter might be an issue though. What sort of crud builds up inside these fiilters? Anyone know? Anyone took an old one apart and had a look at its guts? Could there be a flap of crap momentarily blocking the outlet? Wouldn't be a bad idea to have a sticky post mortem section on the forum. Rather than just binning old parts take them apart or maybe check continuity and resistances across pins and that sort of thing. Post the findings with pictures.

Originally Posted by jfoj

Before I would be jumping on the crank sensor, I would be checking the battery/charging Voltage.

You should be able to bring up the Hidden OBC Menu and be able to monitor you Voltage directly on the OBC display.

Crazy battery/charging Voltage can generate some strange faults and cause the dashboard to light up like a Christmas tree!

Would have never believed this until I witnessed it first hand.

Oh yeah, funny electrical things happen when the voltages aren't in the range they supposed to be

Strange faults could be stalling, erroneous trouble codes, lots of lights on the dashboard and so on.

Many times what happens is the modules have a hard time communicating over the databus when Voltages get below a tolerable threshold for the modules.

I never would have believed it until I knowingly took my E46 on a trip when it seemed to have a difficult time starting. I tossed my jumper box in the trunk and thought maybe the battery was just low for some reason. It was the original battery and only about 3 years old at the time.

Turned out the battery had a bad cell and I ended up running with the jumper box in the trunk connected to the battery for the return trip home.

Out of nowhere the brake light, DSC light, and a few other lights would come on, then turn off after a bit of driving.

Also depending on what tool you are using for reading your codes you need to be careful how you interpret the codes. I know on a few of my cars, I have shadow crank sensor codes all the time. Not sure why, however, I have changed the sensor on my M5 with a new OE sensor and still continue to have crank sensor shadow codes, but no known symptoms. I have discussed this with a few other owners and we have other cars that do the same thing.

Good luck, intermittent faults are a PAIN to deal with. I will take a hard failure almost any day over reoccurring intermittents.

Originally Posted by jfoj

Before I would be jumping on the crank sensor, I would be checking the battery/charging Voltage.

You should be able to bring up the Hidden OBC Menu and be able to monitor you Voltage directly on the OBC display.

Crazy battery/charging Voltage can generate some strange faults and cause the dashboard to light up like a Christmas tree!

Would have never believed this until I witnessed it first hand.

Battery charging voltage consistently 13.8 volts at idle. I have put a meter accross the terminals, ingition off of course, and it reads 12.5 volts which is ok. So I doubt there are any battery issues.

Tell you what I did notice as I was going through the live datasteam at idle. Ignition timings were flicking between 1.5 and 2.6 degrees which is to be expected. The fluctuation, that is. Not sure what the correct range should be because I can't find it anywhere in my manuals. Still there is no hunting. Its quite hypnotic, actually, just staring at flickering numbers. However, every now and then the number would leap up to 41.3 degrees. No perceptible change in idle. Almost like it was for one cycle. Idle speed is 746rpm. It is undoubtedly just an anomaly, because if the timing was that far out the engine just wouldn't turn. You come across anything like that before?

Those were the exact symptoms I had a couple of weeks ago. It only did that once each trip for a few days, never showing any codes. Then it cut out, the DSC and Check Engine lights came on, and it ran with hugely reduced power. Replaced the crank position sensor and it still was in limp home mode with the DSC light on and minimal power. Limped to the local shop, had them use their computer to clear all codes and adaptations that my scanner couldn't do, and it started and has run perfectly since then.

Originally Posted by Tangent_

Those were the exact symptoms I had a couple of weeks ago. It only did that once each trip for a few days, never showing any codes. Then it cut out, the DSC and Check Engine lights came on, and it ran with hugely reduced power. Replaced the crank position sensor and it still was in limp home mode with the DSC light on and minimal power. Limped to the local shop, had them use their computer to clear all codes and adaptations that my scanner couldn't do, and it started and has run perfectly since then.

So you reckon the crank position sensor was the culprit? That was the code I had on the second event. I am having it replaced Monday along with fuel filter so I hope that is the fix. I hate these mysterious problems. I would much rather something just packed up. It does illustrate one debatable point though. There's really no such thing as preventative maintenance because the one that is on it now has only been on it for 7 months. There was nothing wrong with the one it replaced. Just thought I would replace it along with the two cam sensors.

I been thinking about this today. While I will be replacing the crank position sensor and the fuel filter on Monday I'm not convinced that was the problem. Initially I described the symptom as a cut out. But when I think about it a little more it was more like someone suddenly stamping on the brakes but momentarily. Like the brakes just kicked in. The fact that the DSC went into off mode after the second event was a puzzle but I now think it might be a DSC fault and it was the DSC that stamped on the brakes. No DSC codes mind you. Just the cps code. Does this ring any bells with anyone? Feasible? Anyway, I am driving with DSC off for the time being to see how it goes with the new cps and filter. I'll switch it on after a couple of weeks and if it happens again that should give me a clue. Thoughts anyone?

First, I think you should begin that DSC off test now, before you replace the crank sensor.

I do think I've heard of a few incidents where the car activated the brakes on its own...and there are many incidents of wheel speed sensor failings. Not infrequently, those failing have to do with the connector or wire. There's supposed to be a waterproof gasket in there, but I know they can fall out. But, I'm pretty sure you'd find speed sensor codes. I believe it's a myth, that you can fix speed sensors by cleaning the magnets in the hub, but I have read of a few having success with that.

You recall if your car was pushing over to a particular side when it 'cut out'? That would at least help you figure out which side an issue might be on.

Oh, one other thought about this 'brake activating' thought. The brake feeling you're getting might also be just the effect of the engine stopping, which it sounds like it is...then, because the car is moving and in gear, it 'push starts' itself back to life.

Originally Posted by dmax

First, I think you should begin that DSC off test now, before you replace the crank sensor.

I do think I've heard of a few incidents where the car activated the brakes on its own...and there are many incidents of wheel speed sensor failings. Not infrequently, those failing have to do with the connector or wire. There's supposed to be a waterproof gasket in there, but I know they can fall out. But, I'm pretty sure you'd find speed sensor codes. I believe it's a myth, that you can fix speed sensors by cleaning the magnets in the hub, but I have read of a few having success with that.

You recall if your car was pushing over to a particular side when it 'cut out'? That would at least help you figure out which side an issue might be on.

Oh, one other thought about this 'brake activating' thought. The brake feeling you're getting might also be just the effect of the engine stopping, which it sounds like it is...then, because the car is moving and in gear, it 'push starts' itself back to life.

"... it 'push starts' itself back to life". That's exactly why I assumed it was cut out. No pulling at all but you wouldn't expect that if the DSC slammed the brakes on uniformally. I am driving without the DSC and will continue to do so for the time being. I've never really given the DSC much thought but I read up on it last night and the more I read the more it seemed feasible, in spite of the absence of DSC codes. There was no CEL either which you would expect with a crank sensor failure. The other thing that made me think of it was that every now and again I drive with my heavy boots on. The soles have a large lip on them and on occasion, when I am braking, I push the clutch in and my left boot sole catches the lip on my right boot sole and presses the brake as well. I did it today and it was just like what happened on Thursday, but without the dashboard lights coming on. (No, I didn't have my big boots on Thursday night). So the DSC stays off for the forseeable future. Trouble is the default is ON. I have to question the practicality of taking control of the braking away from an experienced human. Its like putting it in the hands of a light bulb. Stupid. I might actually look at disabling it by removing fuses or something.

Originally Posted by RayPooley

... Initially I described the symptom as a cut out. But when I think about it a little more it was more like someone suddenly stamping on the brakes but momentarily. Like the brakes just kicked in. The fact that the DSC went into off mode after the second event was a puzzle but I now think it might be a DSC fault and it was the DSC that stamped on the brakes. ...

The way I'd describe mine would be like cruising along and turning the ignition to off and then back on really quickly, like having it only off for under quarter second or something. I also considered a DSC issue, like maybe a wheel speed sensor was going out or something. But I don't know how a DSC fault would cause the crank sensor code, plus it did that fairly reliably once per drive, usually within 5 minutes of start up for 3 or 4 days before it went into limp-home mode. On a couple of those occasions I was at a stop light at the idle just dropped from the usual ~750 down to a struggling ~400 until I blipped the throttle. It's now been almost 3 weeks with zero recurrence.

Originally Posted by Tangent_

The way I'd describe mine would be like cruising along and turning the ignition to off and then back on really quickly, like having it only off for under quarter second or something. I also considered a DSC issue, like maybe a wheel speed sensor was going out or something. But I don't know how a DSC fault would cause the crank sensor code, plus it did that fairly reliably once per drive, usually within 5 minutes of start up for 3 or 4 days before it went into limp-home mode. On a couple of those occasions I was at a stop light at the idle just dropped from the usual ~750 down to a struggling ~400 until I blipped the throttle. It's now been almost 3 weeks with zero recurrence.

Did you try running with DSC off at all? To see if it had an affect? That's what I am doing at the moment. Did you take any remedial action? Did you find out what caused it?

I pressed the DSC button to disable it (mine's the early single-stage version) and it made no difference. Replacing the sensor and having the shop reset the adaptations and clear the codes my scanner couldn't fixed all issues. Seems pretty definitive that on my car at least the issue was a defective crank position sensor.