ABS - Trifecta - 20pin port not communicating - ECU broken? 1999 E39 5401i M-sport

[SwedenE39]

Okey, long story short.

Car, BMW E39 1999 540iA M-sport.

I went and switched out to my summer tiers, after I changed out the front ones the infamous trifecta appeared, ABS, Break and DSC (anti-spin) in yellow across the dash. I’m rather confident that it’s the front sensors that’s gone bad because I actually drove the car a short trip after I had changed out the rear without any lights coming on.
I bought a new ABS sensor and replaced the left one, the problem remained. I decided to change out the right one as well, the problem remained. I was thinking that perhaps it’s the ABS module but I wasn’t sure. I ordered an iCarsoft 910-II and plugged it in with an adapter to the 20pin underneath the hood.

This has given me headaches for days now, reason being it will not communicate with the ECU. The diagnostic scanner gets power and starts up but I cannot communicate with the ECU when trying to scan ANY module. Now you might think that the 910-II is broken? Well no, ONE TIME I managed to get it to communicate and I could scan any modules just fine, airbags, abs, engine, transmission etc. However, as the simple individual I am I thought that I would work from now on so that I could scan it again and didn’t take notes, and of course no. It does not.
The only information I remember from the ABS scan is
Front left speed sensor (Something like that)
Break line in (Something like that)
(And there was something else)

So now I’m wondering the following.
1. Do I need to flash my ECU at the dealer? (Since I can’t communicate with it using diagnostic tools)
2. Is the ABS module the bandit in all of this?
3. Maybe it’s just the front left ABS sensor that’s still bad?


I’ve checked the glovebox, all fuses are good. I’ve checked the trunk fuse apartment as well, all of them were good. I’ve disconnected the battery to reset the ECU, still does not communicate with 910-II. I’ve tried the OBD2 connection inside the car but I already know that I won’t communicate there and it didn’t.
So now I’m stuck. If I drive the car for too long or let it sit in idle for too long sometimes, if it feels like it, it will go into the lovely “limp-mode”. If anyone knows anything I’d love to get some help.

I’m almost most curious as to why the 910-II could communicate once and never again. I don’t like the sound of buying a new ECU…

Also, the lights never come on instantly. If i leave the car over night and start it up again all the lights are gone until i drive it for a few seconds. If i restart the car after a drive the lights may pop up right away and sometimes they pop up after a second or so of driving....

[bmwdirtracer]

Let's clarify something: You have MANY control units in your car. The "ECU" is called a DME (Digital Motor Electronics) on a BMW. This computer does not control the ABS/DSC. The ABS/DSC is controlled by the ABS/DSC computer. The Transmission is controlled by the EGS. All of these computers, and others, share certain information, via a "BUS" line. These computers converse with diagnostic scan tools via diagnostic lines.

Whether or not your CarSoft scan tool conversed with the various modules once, it is probably the failure item here....if not the scan tool, than the adapter, the wiring, or the connection at the plug. I'd highly recommend that you take the car to a BMW shop, and have the codes read, from all the computers....and have the shop print a list of those codes - not just the code numbers, the WORDS.

The DME is extremely unlikely to be your problem.... I'd say the odds are less than 1 in 100. And although the EGS (Transmission computer) is usually the unit which puts the car into "limp mode", because it puts the transmission in 3rd gear, it is very rarely the EGS which is the root of the problem.

IF, for instance, the MassAirFlow sensor is unplugged, you'll often get limp mode, as well as the ABS trifecta, on some years of E39 with auto trans. If the engine speed signal doesn't reach the EGS or ABS....limp mode. If the vehicle speed signal doesn't make the rounds to all the computers....limp mode.

In short, there's no way for you to diagnose the actual culprit here, until you communicate with at least these 3 computers. If, indeed, the car won't communicate through either the 20 pin diag port OR the OBD2 port, then you've got a wiring issue....or maybe, just maybe but unlikely, a bad fuse.

Take the car to a BMW / Euro shop, and have them read and print all the codes in all the computers.


EDIT: Um, how exactly did you test all those fuses?

[SwedenE39]

Well, this is my first car and I'm 18 years old. I've got a very brief understanding of these sorts of things...

I checked the fuses by just looking whether or not they were blown or not, all of them looked fine.
I could use a multimeter to check if they're working I guess?

Is it true that I should be able to try and disconnect various sensors and try to scan the modules, if I manage to get a valid scan then it should be the sensor I disconnected previous to the scan? I read this somewhere unsure if it's a valid way to diagnose the problem.

The closest dealer is about 25miles away and I'm unsure whether or not I'd like to take that ride risking going in to limp mode, but perhaps I've gotten no choice...

[328 Power 04]

Let's say if a module (not sensors) is bad, or has an internal short on the K line (diagnostic line), then it could take down communication to other modules. It's possible. I have seen this happen on e46 with aftermarket radios, or bad instrument cluster, or bad light control module. If that is truly the problem, to figure it out easier, you find the k-line junction, where all the K-lines meet. You unplug one by one, while testing diagnostic function, in hopes of disconnecting the bad module.


Of course it's possible that your diagnostic tool is bad too.



You can access engine control module (DME) and automatic transmission module (EGS) with the OBD port inside only. For the rest of the modules, you must have the original OBD cap in place, and diagnose outside at the 20-pin round port.

[SwedenE39]

First and simplest, I'm ordering a 25$ OBD2 - 20pin BMW adapter from a trustworthy site which is considerably more than I payed for the first one. (opened up the first one and I'm doubting the wiring between pin 20 and 17... looks rather shady.)

If this does not help me get some modules popping up I'm going to return the iCarSoft Scanner for a different one, then if that scanner does not work I'll try and unplug one module at the time until I get a reading. And now, if that does not work. I'll head over to the dealer to get them to pull codes for me. And if that does not work then I'm gonna have to start digging deeper...

That's the plan for now. The new adapter should be here within the next day or two.

EDIT: FYI I've noticed that my "20-pin" is missing pin-15 which is said to be the "L-line" But I've read somewhere that it's not needed?
Fil 000.jpg

[SwedenE39]

UPDATE!

Okey, well I just went ahead and replaced booth the adapter and got a new scanner at the same time.
Luckily, I can get some readings now which feels amazing.

When scanning the ABS/ASC/DSC I got the following code.
Code:36
"Inlet valve, front left."

To be honest I don't know what that means... I've read somewhere that it could be the break pressure and air bubbles in the break fluid?
I checked a live data stream of the break pressure and it never stayed on 0, if i touched the break it went up and if i let it go it went down but it never stayed on 0. The pressure varied around 0 but never settled down at a specific number.

I recently changed out the break pads on the front, right and left. Maybe it's just so simple that I need to air the front left break?

EDIT:Break pressure varies around these numbers -0.33, 0, 0.33, 0.65, 0.96 0 etc

2 EDIT:
Also pulled a code from the transmission (EGS) . Code 82, CAN ABS/DSC signal.
Then I got some unknown codes from the Steering-angle sensor (LEW)
Code 09 - "The fault code is not found in the database"
Code 01 - "Supply (terminal 30)"
Code 0B - "Sensor/vehicle allocation incorrect or not available"
Code 16 - "The fault code is not found in the database"

[SwedenE39]

Okey well, I don't really know if anyone is following this thread really. But I'll keep it partially updated until I've resolved the problem in hope of helping others in the future!

Sent in the ABS-module for repair to see if that's the thief.

[328 Power 04]

It was very likely the module/pump that went bad, so I think you're on your way to repairing it.