[land sea air]

EDITED original post below. It seems at this point that the issue has been pinpointed to the differential which was replaced. Although the shop says they ordered a manual transmission dif, and their paperwork confirms this, there is an automatic dif (3.15 final gear) instead of a manual dif (2.81 final gear) in my manual car. I confirmed the ratio after watching this video. The short of it is spinning one wheel 10 times while the other is held (in an open dif) while counting the number of times the drive shaft revolves. Multiply that number by 2 then move the decimal left one place (essentially dividing by 10). In my case, backed up onto ramps then carefully raised one side and supported on jack stand. marked the tire and driveshaft with chalk pen and had my girlfriend rotate the tire while I counted (both counting in our heads). 15.75 turns of the driveshaft X2 = 31.5, when you divide that by 10 you get 3.15. The exact ratio suspected in this case.

The symptoms for this problem are cruise control that activates but will not hold speed well, especially over bumps, down hills, or when you press decel. It sometimes will not engage unless you are "helping it" by already accelerating while holding accel. However the cruise works perfectly for me in a lower 4th gear (mistakenly diagnosed by me as lower speeds). It also works more reliably above 80mph.

I am still trying to solve this problem as many people have had it and said the solution is to reprogram the DME but I haven't gotten more detail than that. I hope this revised info helps someone else in the future, I suspect this problem is true for anyone who has swapped diffs to a lower gear ratio. END EDIT*

Hello all! First post here, of perhaps very many considering this car. Did some searching and couldn't find anything specific to my symptoms. Been driving this car for several years now without any major drama, mostly just maintenance. The car recently sat for about 7 months after a dif failure. Since I've been sitting on my ass during the pandemic I was finally able to find a good low mileage unit and have a shop I trust install it without breaking my limited bank. Since getting the car back it has a somewhat intermittent cruise problem, I'll switch to list mode to try and make it easier to understand.

-Cruise control turns on and light will stay on no problem even when CC isn't engaging. Sometimes it will engage with no problem and cut out later, other times it will just barely start to engage before cutting out. It SEEMS to happen more often when the car needs to keep from accelerating to maintain desired speed.

-2000 540i 6 speed with nearly 250k miles. Cruise has always worked smoothly until now.

-Originally thought it was voltage related, found out I had a SECOND bad alternator soon after dif replacement. (it has been a rough 2 months). Now alternator is fixed and cruise is still not working.

-Car is throttle by wire with all buttons for CC on steering wheel, to me this eliminates many possible failure points.

-Only other warning light is SES for air injection system (I suspect clogged ports) and codes that havent cleared from storage yet for an unhooked coolant sensor after the alternator was put in. This also seems to eliminate many failure points (abs) to me

-Visually, functionally checked brake and clutch switches, both seem to be working, brake lights work fine.

-I just got a creator 310+ but it seems many things give me a communication error, I can check and clear codes, see live data and ecu info, and even clear throttle whatchacallit. but it wont let me look at any of the sub systems. user error?

Any help would be much appreciated. I hope this long ass post makes sense!

 

[edjack]

Take it back to the mechanic. He must have done something wrong.

 

[land sea air]

I'm not sure what you mean. This happened before the alternator was replaced and I'm not sure how dif replacement could cause this issue. I did visually inspect the wheel speed sensors (I think it uses data from the front or all 4 instead of rear like earlier models?). Couple things i forgot, the trans oil was done during dif job (again not sure it would have anything to do with cc) and i replaced the ignition switch as a relatively cheap last ditch effort before it went in for the alternator. Side note, would a dinan tune affect the ability for the c310 to work properly?

 

[Doug Huffman]

I have had a few CEL and have come to associate CC problems with the CEL.

My CC is supposed to increment SET speed by 5 MPH with each click past point of resistance. With the CEL lighted it usually does not increment by 5. Last year I had to put up with an EGR valve CEL for almost 2,000 miles, and be reminded every time I used the CC - and I ALWAYS drive on the CC.

 

[land sea air]

Hmmm. The thought had crossed my mind, the secondary air codes didnt start until after it sat for months. I can clear the code and still have CC problems while the light is off. Light comes back usually on first cold start when SAI comes on.

 

[land sea air]

:bump: So after a few long drives today here's what i have. SES light on or off same issues. Pushing minus/decel causes cc to cut out almost every time. It can run smoothly and maintain speed for some time and accelerate with plus button no problem then cut out abruptly. Green light stays on in cluster as always. Does creator 310+ need to be adapted to fit under hood port or should it be able to perform its functions through OBD?

 

[Chedley]

Hmmm. The thought had crossed my mind, the secondary air codes didnt start until after it sat for months. I can clear the code and still have CC problems while the light is off. Light comes back usually on first cold start when SAI comes on.

You must address the cause of the CEL or SES, and fix it, for the cruise control to work correctly. :angel: Simply clearing the error codes does NOT fix the problems.

 

[land sea air]

The problem with that is in this case the SES is likely being caused by clogged SAI ports in the head. Thats pretty sad. Can anyone else confirm CC not working correctly simply because codes are stored?

 

[land sea air]

Ok here is where we are at now. I ordered the 20 pin adapter for my creative (didn't realize I needed that) and it allowed me to take a look at the abs system. The codes I pulled were implausible signal for both front wheel speed sensors and code 59 undervoltage (not sure what this one means) I pulled the driver sensor and visually the head looks clean wires ok etc. but I will probably have to replace them I imagine. I am not completely discounting the ses light theory and I did order a secondary air delete kit from Garry Peterson at e36-electronic (he makes them for the m62tu even though it is not listed) but I think it is far more likely that the wheel speed sensor could be the culprit even though it is not triggering a light on the cluster. Does this make sense?

 

[Chedley]

Not really...I'd take it step by step :
1-- ABS Code 59 (under-voltage) may be caused by a low battery -- yep, the battery/alternator thing again. Check it, and recharge it. Does the Creator scanner logs the battery's voltage at the time of the error, like INPA does ?

2 -- The implausible signal for wheel speed sensors indicates a sporadic weak signal from the wheel sensors. Not necessarily bad sensors. I'd inspect them, clean them out, and make sure their connection is good and clean. Then erase all the errors and test again.

3-- And the CEL or SES. Did you figure out which error code triggers it ??

 

[land sea air]

Thanks for the reply!

1- I believe voltage is good, I've put a couple hundred miles on the car this week (commuting to dog sit) while at rest with the key on it shows 12.5/12.6 on the creator and while driving its mid to upper 13s on the cluster. I'm wondering what else the undervoltage code could mean if it isn't battery/alt. Could it be as you stated the wheel sensors are sending low voltage? EDIT: to answer your other question no the creator just shows the codes, voltage has to be checked separately.

2- I was able to pull the driver sensor no problem with the limited tools I have (again, dog sitting away from home). It looked ok with minor dirt on the end, I cleaned it up and reinstalled it. Unfortunately I don't have brake clean with me to spray in its hole, perhaps things were gummed up from clearing the rotors that sat for more than 6 months. I could not loose the pass sensor with the torx bit and did not want to risk stripping it so I'll make sure I have the 5mm hex and some brake clean with me tomorrow. Starting the car and moving it off the ramps was not enough to have any of the codes come back after clearing them so I will scan again after the long drive home. I went ahead and ordered a pair of sensors since no one had them in stock near me.

3- Yes sorry, I have known all along that the light was because of a secondary air issue, when I first returned the car to my house after sitting for so long the pump was making noise and the light was on so I replaced it and the valve. I also replaced the lines and smaller components on top of the engine to no avail. Carbon blockage inside the sai ports (inside the heads) is not uncommon on these engines. The kit I ordered will tell the 02 sensors what they want to hear and allow the SES to be cleared permanently.

So I have 2 potential solutions right now on their way, the sensors are not costly so I don't mind doing them and I need the SES light gone one way or another for emissions in MD. I have not been able to spend as much time on the problem as I would like because of the dog sitting

When I got the adapter for the creator and cleared the abs codes for the first time last night I was able to drive around at low speeds for quite some time with the cruise active no problem, when I got on the highway it started dropping out of cruise again so perhaps that is when the codes trigger (I can't drive the car with the creator plugged in under the hood)

 

[land sea air]

Oddly enough after the 50ish mile drive home the abs codes had not returned although cruise is still cutting out a high speeds, seems much less of a problem at lower speeds. Tomorrow i will pull both sensors and clean them more throughly.

 

[Chedley]

Good news the ABS error is gone. It is probably a sensor connectivity problem ?!
I'd ignore the cruise control thing for now, unless it is causing the CEL.

 

[land sea air]

Well that was the issue that led me down this rabbit hole, since before the car sat i had no warning lights or issues. Here's hoping its a wheel speed sensor issue and not something with the module.

 

[dtw]

Sounds like you installed a differential with a ring/pinion ratio that is different from that which was originally equipped on your car. The resulting wheel speed variance exceeds the sensitivity limit in the DSC module. The most visible impact is that cruise control is canceled. Your options are to install the correct differential, or have your DSC module programming updated.

 

[land sea air]

Oh now this is a route that i had not considered at all. Is that possible with the 540i? Were there different ratios available? Could this be fixed with inpa? In the mean time I'm just awaiting parts. The codes in the abs module have stayed gone but the cc still drops out at higher speeds.

 

[land sea air]

So it looks like the automatic and manual have different ratios, if mine ended up with an auto diff then the ratio would be different. Would this not trigger a warning light of some sort constantly having incorrect wheel speed?

 

[dtw]

So it looks like the automatic and manual have different ratios, if mine ended up with an auto diff then the ratio would be different. Would this not trigger a warning light of some sort constantly having incorrect wheel speed?

You would think that you would get warning lights on the dash, but I have never heard of it happening.

If you ordered a replacement diff, you probably received an auto diff if you did not specify. Obviously the 6M diffs are much more rare. Just out of curiosity, how did yours fail?

INPA does not do much in the way of coding/programming. Reset adaptations, some basic recalibrations, sure. You would need NCS Expert and/or WinKFP for this issue.

Check out some of the auto/manual conversion threads, there's documentation of this issue and how to deal with it out there.

I am trying to think if I have ever seen any CEL codes that impacted cruise functionality, none come to mind. Certainly not SAI. Doug's post about the EGR valve is interesting though.

 

[edjack]

The E39, AFAIK, does not have an EGR valve. It uses valve timing to effect EGR control.

 

[land sea air]

In some ways it almost makes sense, the difference isn't enough to confuse cc at lower speeds but higher speeds the difference is greater and therefore problem. Its hard to imagine this wouldn't trigger a trifecta or at least one light. Once I'm back in front of a computer ill do n some research on the conversions. I've always had trouble with the ses light in itself being the problem but other people swear by it.