[NZE90]

I've never played around with an EKPM module before, so can't really comment on it's specifics. I would open up the module and check the circuit board for water damage?

I thought the CAN resistor was in the JBE on the E90 but could be confused with another model. I know F3x cars had them in the modules.

[NZE90]

Sorry, you are right, there is one resistor in the EKPM, so you should have 120 ohms between pin 16 and pin 8 of the EKPM with it disconnected. And there's also 2 resistors in the JBE.

An EKPM2 is the correct module for your car, so i wouldn't worry too much about it.

[JoshS98]

Originally Posted by NZE90

Sorry, you are right, there is one resistor in the EKPM, between pin 16 and pin 8. And there's also 2 in the JBE.

No reason to apologize, your comments have helped an insane amount. Thank you again. If you’re ever on Vancouver Island I owe you a drink or something! And everyone else who has stopped by to give advice! Absolutely amazing community here and thrilled to have an e90 as my first proper car


Finding documentation on the these resistors has been rough. Best one I found I’ve attached below in case anyone comes across this thread and needs it.

Seems to be some teaching material based on the pages with questions at the end of the sections.

Was messing around with the EKPS more and found out my resistance seems to be between the PT-Can high lines instead of between the High and Low lines.

Specifically pins 8 & 9. Everything I’ve read says the resistance should be between high and low.

Seems like the issue lies there. I did try some contact cleaner and an old toothbrush on the inside of the EKPS. There was some corrosion on the pins, a bunch on the screws holding the board that flaked off upon unscrewing. Hasn’t made any difference though.

Gonna pick a new EKPS module tomorrow and hopefully be able to add a solved tag to the thread.

[JoshS98]

Well, looks like that wasn't it. Unfortunately think I am back to square one.

Unsure what's going on at this point or what to even try.

The new EKPM module also has the resistor between pins 8&9 which are both PT-Can High lines.

Measuring from the connector that attaches to the EKPM, I'm also getting no ohm reading with the DSC plugged in.

I have continuity on the PT-Can from the DSC to that big white box of electronics.

Both seem to connect through the JBE like you mentioned, wondering if the issue lies in that part.

I can't read the DSC resistance on the EKMP end of the line.

I can't read the EKMP resistance on the DSC end of the line.

Both the modules have a resistor that I've verified.

The DSC has continuity to that white junction box type thing. No idea the proper name.

But once I get to the EKPM2 side of the network that DSC connection dissapears.

Haven't tested that the EKPM gets continuity to that.

But the DSC resistance should be able to be read on the EKMP2 side. So that is an issue that does need solving and does exist.

[JoshS98]

Alright so sat down with a coffee and really really started going over everything again and think I might be on to something.

My EKMS reads resistance, albeit across the pt-can H pins instead of the Pt-can H & L pins like it should according to documentation.
But I don't think it matters unless I somehow got 2 modules that failed the exact same way.

So my DSC has resistance. I've confirmed continuity from the X18303 connector to X6021.

If you go back to the post where I tried that, you'll notice I had continuity on Pin 30 (pt-can H) to 3 but not to pin 1. And continuity on pin 15 (pt-can L) to pin 4 but not pin 2.

Looking at this wiring diagram, x6021 has pin 3 go to pin 1 and pin 4 go to pin 2 after going through the X8091/X8090 connectors.

Since I have continuity from the DSC to one side of the X6021, but not the other makes me think my problem lies right there.

Unfortunately that seems to be the transmission control unit A7000a. I do not think I even remotely have the skills required to gain access to that.

Going to try to confirm this by probing at specific points.

If my theory is correct I can take an ohm reading for the DSC on pins 2&4 at the X6021. It should show 120ohms. I'll also check pins 1&3 to confirm no DSC signal passing through to those.

Then I can take a reading at the a4010 junction box. If my theory is correct I will only be able to see the resistance provided from the EKPM module. Unplugging that should show no readings.

That should prove my theory that my DSC resistance is disappearing at X6021.

This does get a little confusing however because my transmission seems to be absolutely fine. Drove the car for a few days before starting to work on what I thought was just a DSC issue and never noticed any weird shifting or such.

What also confuses me is in the diagram for the X6021 connector it shows a significantly different connector to what I have. Attached a photo of the connector in ISTA and the one in the car.

Anyone want to absolutely make my day and tell me I'm completely wrong and that I should not have continuity from pins 3 & 1, and pins 4 & 2 at X6021? Or that it could be something else besides the transmission controller?

[JoshS98]

Found a pinout for x6021, will attach here. That pinout shows Blue/Black and yellow wires heading off to the transmission controller.

My x6021 has none of that, like seen in the photo of the connector above I only have the top half of this wiring diagram actually wired up.


I am beyond confused, nothing is making any sense anymore.

[JoshS98]

This thread has been an absolute rollercoaster and I feel like I keep just info dumping. I've essentially dedicated most my waking hours over the last 3 days digging into this, so please excuse me.


So my transmission is communicating completely fine, I've driven the car. INPA/ISTA and everything shows it. (sure maybe something is wrong but let's just say it's not). It's on my module tree, it's communicating. I don't know why the wires aren't in the connector, I don't care anymore. It's working. I have no error codes on it.

If my DSC connection is somehow not completing between pins 3 and 1, 4 and 2. Is there any reason I shouldn't just add my own piece of wire into the connector and essentially short those together?

Sure I haven't found why, but its fixed

The wiring diagram shows it's supposed to continue. It's not. Somehow the transmission has continued on communicating just fine.

I can try blasting the area with plastic safe contact cleaner first but there's no corrosion I could see when I was testing continuity yesterday.

Maybe some wire is loose? I threw a video on YouTube of me poking around the box. No idea how these are supposed to look in my gen of car.

[JoshS98]

Oh my god,

those are little u things at the end of lines are connectors on the wiring diagram and the dots are splices.

So my connector ain't connecting right. Wire loose or corrosion???

My transmission still spliced in thats why its working!!

I shouldn't be celebrating so early but this is it. I feel it

[NZE90]

Something worth considering.......if someone else has been trying to diagnose this issue, have they been shoving probing pins into the sockets in the connector and destroying the contacts inside the sockets? I have seen this problem so many times it's not even funny.

The only way to test this is to have the correct size pin for the connector socket and insert it in whilst feeling for drag on the pin (indicating good contact) if there is no drag, there will be a poor or no connection.

[gbalthrop]

Originally Posted by JoshS98

Found a pinout for x6021, will attach here. That pinout shows Blue/Black and yellow wires heading off to the transmission controller. My x6021 has none of that, like seen in the photo of the connector above I only have the top half of this wiring diagram actually wired up...

You said in prior post: "I had continuity on Pin 30 (pt-can H) to 3 but not to pin 1. And continuity on pin 15 (pt-can L) to pin 4 but not pin 2." As I understand your issue, "29 DSC" does NOT appear on Module ID List, & you have numerous fault codes related to NO MESSAGE from DSC. Those facts suggest an issue in the PT-CAN wiring between the DSC Module & JBE connector X14271/1 & 2.

As I understand it, your EGS (Transmission Module A7000) is communicating, & appears on INPA Module ID List, as well as EKPM, Fuel Pump Module. That suggests there is an issue at X6021, BOTH with RedBlue wire at X6021/3, & ALSO with the Red wire at X6021/4. Since you have the E-box open, I would suggest, with Ignition OFF, & BOTH Connectors X18303 at DSC, & X6021 in Ebox Disconnected, TESTING for CONTINUITY (Near-Zero Resistance/Ohms) in BOTH:
A) Red wire between X18303/15 & X6021/4 (PT-CAN Low) &
B) Blue/Red wire between X18303/30 & X6021/3 (PT-CAN High).

Carefully inspect pins & sockets at X6021, particularly 1,2,3&4, for any corrosion or damage. If DSC Still is not communicating, & you have correctly tested for Voltage Supply & Ground, at X18303 at DSC, then retest for continuity in Red wire & also in Blue/Red wire, between X6021 & X14271/2 & 1.

I have NOT examined X6021, so can't tell exactly WHERE the Yellow & Black "Bridge" wires are attached, but that appears KEY.

Please confine testing to the PT-CAN wiring & connectors as described.
George

[JoshS98]

Originally Posted by NZE90

Something worth considering.......if someone else has been trying to diagnose this issue, have they been shoving probing pins into the sockets in the connector and destroying the contacts inside the sockets? I have seen this problem so many times it's not even funny.

The only way to test this is to have the correct size pin for the connector socket and insert it in whilst feeling for drag on the pin (indicating good contact) if there is no drag, there will be a poor or no connection.

I’ll keep an eye out for that, been eagerly waiting to get in there but it’s been raining and it’s super foggy and damp out. I’d hate to cause more problems letting moisture get inside there while working on it.

Was a single owner before me, super sweet older man. Dude was so impressed when I pulled out an obd reader to check for codes. Didn’t believe me when I told him what an OBD port is and how anyone can use them.

He only got it serviced at Henneken auto in Vancouver Bc. No experience with them personally but family have used them for 20+ years with no problems.

Their website claims many years of experience on what only seems to be a 3 man team. So hopefully they know better than to destroy connectors. I did email them inquiring if I could get their last service write up on the car. Even offered to pay but haven’t heard back. Just curious to how the diagnosed the DSC failing and ignored the LDM.

Hopefully just a dirty connector or something. Definitely didn’t have any continuity happening when I tested last night.Only took 14+ hours for it to click. If I fix that, everything else that’s been testing as working should fire right up.

[JoshS98]

Originally Posted by gbalthrop

You said in prior post: "I had continuity on Pin 30 (pt-can H) to 3 but not to pin 1. And continuity on pin 15 (pt-can L) to pin 4 but not pin 2." As I understand your issue, "29 DSC" does NOT appear on Module ID List, & you have numerous fault codes related to NO MESSAGE from DSC. Those facts suggest an issue in the PT-CAN wiring between the DSC Module & JBE connector X14271/1 & 2.

As I understand it, your EGS (Transmission Module A7000) is communicating, & appears on INPA Module ID List, as well as EKPM, Fuel Pump Module. That suggests there is an issue at X6021, BOTH with RedBlue wire at X6021/3, & ALSO with the Red wire at X6021/4. Since you have the E-box open, I would suggest, with Ignition OFF, & BOTH Connectors X18303 at DSC, & X6021 in Ebox Disconnected, TESTING for CONTINUITY (Near-Zero Resistance/Ohms) in BOTH:
A) Red wire between X18303/15 & X6021/4 (PT-CAN Low) &
B) Blue/Red wire between X18303/30 & X6021/3 (PT-CAN High).

Carefully inspect pins & sockets at X6021, particularly 1,2,3&4, for any corrosion or damage. If DSC Still is not communicating, & you have correctly tested for Voltage Supply & Ground, at X18303 at DSC, then retest for continuity in Red wire & also in Blue/Red wire, between X6021 & X14271/2 & 1.

I have NOT examined X6021, so can't tell exactly WHERE the Yellow & Black "Bridge" wires are attached, but that appears KEY.

Please confine testing to the PT-CAN wiring & connectors as described.
George

Thank you so much for the extremely well written and thorough response! I really appreciate the help!

Before sealing the box last night due to incoming rain I was able to test X18303/15 & X6021/4 as well as X18303/30 & X6021/3. There is perfect continuity.

I’ll have to wait till tomorrow to test continuity between X6021 and X14271/2 & 1. It’s still quite damp outside and I’d hate to allow moisture inside the e-box.

Can also confirm there is voltage supply and ground, at X18303.

Seems like the X6021 connectors are easily removable from their E-box mounts and have “bridges” on the bottom side. I should be able to carefully take them out and find exactly where the issue lies

[gbalthrop]

Originally Posted by JoshS98

... Seems like the X6021 connectors are easily removable from their E-box mounts and have “bridges” on the bottom side. I should be able to carefully take them out and find exactly where the issue lies

I've Never done what you describe, but my interpretation of the SSP wiring diagram is that the connection of EGS to PT-CAN Hi/Lo (Yellow wire & Black wire) is done on bottom side of X6021. Since EGS appears on "F2-ID", but DSC does NOT, it appears you have continuity from EGS to JBE "Hub", but NO continuity between DSC & JBE hub.

It would educate ALL of us if you would take the time to attach PHOTOS that show the configuration & wiring of X6021, particularly the bottom where (apparently) the Yellow & Black wires from EGS connect.

My SWAG, if you have continuity in BOTH Hi & Lo PT-CAN wires to X6021, is:
Bad connection between X6021/3, 4 to Black & Yellow "Bridge" wires. SOMETHING at X6021 appears amiss (FUBAR ;-)
George

[JoshS98]

Originally Posted by gbalthrop

I've Never done what you describe, but my interpretation of the SSP wiring diagram is that the connection of EGS to PT-CAN Hi/Lo (Yellow wire & Black wire) is done on bottom side of X6021. Since EGS appears on "F2-ID", but DSC does NOT, it appears you have continuity from EGS to JBE "Hub", but NO continuity between DSC & JBE hub.

It would educate ALL of us if you would take the time to attach PHOTOS that show the configuration & wiring of X6021, particularly the bottom where (apparently) the Yellow & Black wires from EGS connect.

My SWAG, if you have continuity in BOTH Hi & Lo PT-CAN wires to X6021, is:
Bad connection between X6021/3, 4 to Black & Yellow "Bridge" wires. SOMETHING at X6021 appears amiss (FUBAR ;-)
George

Had a chance to work on this today when the rain subsided.

Highly recommend removing the “bottom” half of the cabin air filter mount. The wiring harnesses just clip on and off. Didn’t remove this my first time opening the box and it was a completely struggle.

Inside the ECU box you can actually take the entire slab of plastic these clips are on out. Super easy latch. Slid that out and found this

The yellow and blue/black wires on the bottom side of X6021 lead off into the wiring harnesses that cross the engine bay. Seems to go down on the driver side of the engine. Wasn’t able to fully follow it.

Looking at the PT-Can wiring diagram these seem to be the “splices” leading off to the TCU.

What I can’t find is the actual splice.

The wiring diagram of X6021 makes it seem like the other side of this connector should continue right on to X14271 with just a splice leading to the TCU.

That splice doesn’t exist here, the connector for X6021 is the wrong one according to inpa. It also doesn’t have any direct connection or “bridge” between 2-4 and 1-3 like inpa implies.

I tested the connector and found no continuity between corresponding pairs. So somewhere in that wiring harness lies my issue.

Followed that back and unfortunately found a spot where it seems chewed and has rodent poop.

Definitely not the best outcome. Looking at wiring harnesses I found a whole transmission one for $200. No idea the exact part I need. If someone could let me know that would be great. Also if anyone knows the book labour hours for maybe replacing that so I’d have some idea of the damage here.

Circled important areas in photos. Also the wiring harness these lead to


The wiring diagram makes me want to just bridge these myself as bmw makes it seem like they were supposed to be and the transmission wires are just a splice or something.

But I know there’s potential for more issues here especially with wet weather or anything.

Inspected the engine bay thoroughly and found no other signs of chewed cables. Pretty lucky in that aspect I guess.

[JoshS98]

Super hard to get a photo of the area but using multiple flashlights I can’t find any wires with damage only the wrapping around the wires. It’s a super tight and deep area so I’m going to order a endoscope and look more.

Did a little more probing with a DMM and couldn’t find any shorts between wires going through that harness.

Totally forgot to test them to chassis ground will do so in the morning

[gbalthrop]

Originally Posted by JoshS98

... The yellow and blue/black wires on the bottom side of X6021 lead off into the wiring harnesses that cross the engine bay. Seems to go down on the driver side of the engine. Wasn’t able to fully follow it.[Those SHOULD go to X8500 Round Connector at Right-Rear of Transmission (search "transmission" for "STA" Connector View, Pins #2 & #6, Lo & Hi)]

Looking at the PT-Can wiring diagram these seem to be the “splices” leading off to the TCU. [My interpretation of that is the X6021 Connector provides the "splice" or connection of Transmission PT-CAN wires to Red & Blue/Red PT-CAN wires. It ALSO provides connection of Red & Blue/Red Hi/Lo wires from DSC to other "twisted pair" of Hi/Lo wires going to X14271/1 & 2.]
What I can’t find is the actual splice...

Perhaps I'm missing something. Look at your 2nd Photo. It show TWO "Twisted-Pairs" of Red & Blue/Red Lo/Hi PT wires going into that connector. Now look at your 3rd Photo. It shows ONE "Twisted-pair" of Yellow & Black(/Blue?) wires which you say go across the engine (& down to transmission?).

Is there a 2nd "twisted-pair" of Yellow & Black wires? I don't see any reason there SHOULD be. The X8500 Connector (PIB) at Transmission ONLY shows TWO PT Lo/Hi wires, connecting at X8500/2 & 6. Note the SSP shows .5 mm-sq cross-section for Transmission wires but smaller .35 for Red & Blue/Red PT Lo/Hi wires. That appears consistent with your photo.

Assuming you STILL have EGS shown on ISTA "Tree", or on INPA F2 ID, but NOT DSC, then I don't see any issue with Yellow & Black (or Black/Blue) wires going to transmission. If there were Open Circuit, there would be NO EGS communication with JBE Hub. If there were "Short", that would crash entire PT-CAN Bus (DME, EKPS, EGS & DSC).

My SWAG is that there is an issue in X6021 itself, OR with connection between the TWO "Twisted-pairs" of Red & Blue/Red PT-CAN wires.

As I interpret the "Powertrain CAN bus" SSP, there SHOULD be CONTINUITY between X6021/1 & 3 (sockets #1 & #3) AND there should be continuity between X6021/2 & 4. You could "Jumper" those sockets (effectively connecting the TWO PT Twisted-pairs), and see if you NOW have DSC communicating.

I'm sure the guys at Munich had a reason to draw the PT SSP the way they did, but at my pay grade, it's confusing.
George

[JoshS98]

Originally Posted by gbalthrop

Perhaps I'm missing something. Look at your 2nd Photo. It show TWO "Twisted-Pairs" of Red & Blue/Red Lo/Hi PT wires going into that connector. Now look at your 3rd Photo. It shows ONE "Twisted-pair" of Yellow & Black(/Blue?) wires which you say go across the engine (& down to transmission?).

Is there a 2nd "twisted-pair" of Yellow & Black wires? I don't see any reason there SHOULD be. The X8500 Connector (PIB) at Transmission ONLY shows TWO PT Lo/Hi wires, connecting at X8500/2 & 6. Note the SSP shows .5 mm-sq cross-section for Transmission wires but smaller .35 for Red & Blue/Red PT Lo/Hi wires. That appears consistent with your photo.

Assuming you STILL have EGS shown on ISTA "Tree", or on INPA F2 ID, but NOT DSC, then I don't see any issue with Yellow & Black (or Black/Blue) wires going to transmission. If there were Open Circuit, there would be NO EGS communication with JBE Hub. If there were "Short", that would crash entire PT-CAN Bus (DME, EKPS, EGS & DSC).

My SWAG is that there is an issue in X6021 itself, OR with connection between the TWO "Twisted-pairs" of Red & Blue/Red PT-CAN wires.

As I interpret the "Powertrain CAN bus" SSP, there SHOULD be CONTINUITY between X6021/1 & 3 (sockets #1 & #3) AND there should be continuity between X6021/2 & 4. You could "Jumper" those sockets (effectively connecting the TWO PT Twisted-pairs), and see if you NOW have DSC communicating.

I'm sure the guys at Munich had a reason to draw the PT SSP the way they did, but at my pay grade, it's confusing.
George

Was real hard to get a view, even cutting zipties didn’t help much.

But I did find a second pair leaving x6021 on the back side of the wiring bundle. I’ve attached photos.

Went to start the car and read the codes before anything, lo and behold I now have a transmission communication error.

At this point the rodent droppings and chewed wire tape has to be something more.

I found a replacement wiring harness online, they seem to be $50-$100.

Luckily most of the connectors themselves seem to be inside the e-box. There’s just two connectors once the harness leaves. A grounding nut (easy) and the circular transmission plug.

Planning to replace this myself, hoping to get some insight on if I’d need access to the bottom of the car to plug this into the transmission.

Watching videos and inspecting the engine bay has revealed that removing the intake manifold seems to allow access deep enough to where the end of the cable ends. Should also allow me to inspect it more closely to see if it’s just a case of one or two wires that I can solder and cover with heatshrink.

Mainly now trying to figure out if I need access below and should be getting the car up on jackstands before starting the whole harness replacement if I go that route.

[JoshS98]

So endoscope arrived from Amazon this morning.

Underneath the intake manifold seems to be just damage to the plastic wire wraps (white wire in photos). Transmission harness however is absolutely destroyed.

Have a transmission harness on the way, hoping I can get it installed at home without needing to pull the engine forward like so posts I’ve seen suggest.

Can’t fully find anything solid on this though, at least not for the n52 engine.

darn rats

[NZE90]

Sorry, i've been out of action for a few days with moving house and a sick child (not fun at all)

Looks like you've been getting some great help from gbalthrop so there's not much more i can add, other than agreeing with George that there seems to be two pairs of PT-CAN wires going to the EGS, which then seemingly join at splice x8090 and x8091 in the harness down near the transmission connector. So the two going to the EGS must be intact, but the other two broken which would explain the issue with your LDM and DSC.

But it should have also knocked out your FRM as well if the PT-CAN tree order is correct
Anyway, you seem to have found the issue. Great work!

[NZE90]

It would be interesting to open up that old harness and confirm if there is two sets of PT-CAN wires in there if you have time.

[JoshS98]

What a day, transmission harness is on. DSC coded and system bled. I have some pics, was super cramped and hard to get any. Don’t have a lift so. Definitely can take more if needed. The two sides actually splice at the end and go to the transmission connector.

Still got two DSC codes, about valve adjustments. Reading about them I just gotta bleed the system and then initiate them or something. Bled the system but stopped before clearing codes

Just gotta handle the ambient air temperature sensor and the AUC sensor and I have no codes. And the rest of the DSC stuff

I was getting absolutely bit up by mosquitos so I stopped for the night.


Let’s get into the cool stuff though.

No idea when someone else is gonna have this issue but it is 100% possible to replace your transmission harness without moving or dropping the engine and transmission. All it requires is fish tape when pulling the old cables out and tons of patience and swearing to get the new one in.

I don’t mind trying to make an in depth guide if needed.

Short version of what I did is as follows.

I knew the harness was useless from rats so once I got it unplugged from the transmission I reached my hands up and got it out from two metal clips attached to the transmission itself. No idea how these work, couldn’t see, just get the cable out of them.

From there you can pull the wire down a bit and get more access to it. This let me cut the transmission plug off completely. This gave me access to wrap the wires directly around the fish tape.

I slowly had a helper pull the old harness up past the engine as I fed the fish tape through the bottom.

Once the old harness was out, I planned to tape the new one to the fish tape and pull it through.

To do so I disconnected the plastic elbow at the end of the transmission side of the harness. This let me manipulate it more and get it through the areas I needed to

From the bottom of the car you can reach up on the driver side of the transmission and reach the only plastic clip that was holding the old harness on. I pulled it straight down to the ground. Don’t worry it’s not on the passenger side.

Now over where the what I think is called “shift linkage” you have just enough space to wedge the connector back up to the top of the transmission. This is only possible with the elbow taken off.

Once past this super tight area you just need to slowly pull the cable to the passenger side of the transmission using the fish tape.

This took some time, some viewing using an endoscope and a lot of wedging my hands up where they barely fit to push and pull.

Eventually I made it over, was able to reattached the elbow. Then I could plug it back in and move the cable to the correct spots and reclip into the metal clips.

Yeh it might not be the exact right path for the wire but it’s not crushed or crimped anywhere. It’s not able to fall anywhere it can get damaged and it’s exposed to the same heat and elements. It’s possibly off by like 2 inches at most.

End of the day I didn’t have to pull my engine or transmission. I did this at home with a $30 roll of fish tape and some duct tape to attach the new cable.


You might worry about the cables popping out of the connector head when pulling it with the fish tape.

On my old connector I cut off I tugged real real hard on the cables and the plastic cable sheathing broke first. The copper stayed inside the connector. So don’t worry, they can take some pulling.

[NZE90]

Great work! If you go into the "service function" tab in ISTA you will find the DSC hydraulic unit adjustment service function which should take care of those codes.