5hp24 and DME 5.2 limp

[jeffbebe]

Not an E31 enquiry but after owning one for years I know there is a lot of expertise in this forum. Hoping someone like TimM can help out!!

After selling my 850i during the Covid boom, I decided to convert my E36 338i wagon into a V8 tourer! I bought a cheap healthy 97 E39 540i - one of the few non-vanos V8s that came with a steptronic 5hp24.

The goal was to build a fast and comfortable wagon so i planned to keep AC, add ASC and use the steptronic gearbox. Early on, I made the decision to swap the 5.2.1 DME for a 5.2 from a 96 E39 to make EWS play nicely in my e36 (the alternative was to modify an E46 cluster or run have the e39 cluster hidden in the dashboard somewhere… not very elegant).

18 months later, and I’ve pretty much finished. The engine is running super smoothly with no errors and I was finally able to test drive it today.

Unfortunately, the gearbox is stuck in 4th gear - a la limp mode. There is no trans failsafe error and the only errors logged are the magnetic shift lock (I removed it) and “canbus version error”. I unplugged the ASC and established the canbus error is between the TCU and DME.

So, to cut a long story short, I have three questions I’m hoping y’all can help with…

1) Could the shift lock error cause the gearbox to run in limp?? I doubted it would but perhaps I was wrong.

2) Has anyone ever come across the “canbus version error” before? The interwebs are of no help on this issue.

3) Does anyone know if DME 5.2 will NOT work with a 5hp24 TCU? Or know if there’s something I need to do to make it work? (Beyond retrofitting ASC which I’ve already done so the DME gets wheel speed from all 4 wheels).

Thanks in advance. Pic of the car below to show just how little room there is in an e36 for an M62 with AC and ASC!! And yes, I’ll wrap and tick the loom away once the gearbox works properly!!

https://flic.kr/p/2oWDLAr

[purplecty]

What happens if you run the original DME and EGS(TCU) combo together? Do you still get the canbus version error?

[jeffbebe]

Haven’t tried. Different DME connector so we’d have to switch looms and rewire the car. Not a small job unfortunately. Plus the 5.2.1 won’t work without the e39 or an e46 cluster.

[Hyper]

E36 338i wagon... Does anyone know if DME 5.2 will NOT work with a 5hp24 TCU?...

I'll assume a 328. We (in US) got to import them just recently. A V8 project would make it worth the effort.
I saw a factory doc that says there is a design break on the 5hp24 TCU, 88 pins v 134 pins, right around the year you're messin' with.
Have no further info.

[jeffbebe]

Yep, 328i. We used the engine loom from the older 5.2 car but the TCU loom was from the 5.2.1 so will have the correct pin out. The TCU receives canbus signals from ASC and DME. Since the canbus version error appears to be between the DME and TCU, I’m guessing the canbus signals from the DME are not being recognised correctly.

[Hyper]

... We used the engine loom from the older 5.2 car but the TCU loom was from the 5.2.1...

I anticipated this possibility, and it was my go-ahead for alerting to a potential for mixing protocols and features across a design break, iow's later TCU with earlier DME.

[Timm]

No problem with the shift-lock solenoid missing - you get a TRANS FAIL-SAFE PROG (if the cluster communicates with the DME) but you still get all the gears. The problem is that the DME cannot communicate with the EGS because of the version mismatch.

I understand why you moved away from the E39 system because of the IKE working as the gateway, but the E31 DME/EGS pair would probably be a better match, designed around the same time as the E36 and sharing quite a few systems. Unfortunately, the E36 Instrument Cluster is very different to the E31 with the E31 being a dumb display whereas the E36 is a stand-alone unit....

[jeffbebe]

Thanks Tim. Not really what I was hoping but mostly what I was expecting. I’m guessing there is no way around that but I have a very clever mate who will make it work if it’s possible. Most likely I’ll need to go back to 5.2.1 and modify an E46 cluster - which I think will be easier than finding a 5hp30 (I don’t want to redo a new set of cooling lines t fit!!)

At least the E46 cluster will show gear selection which will be a nice upgrade.

[jeffbebe]

Did some on road diagnostics and we have now been able to confirm that the issue is definitely between the DME 5.2 and GS8.60.2 TCU. According to realoem there was one year of production 9/96-9/97 when both E38s and E39s and some 840s got the 5hp24 gearbox with a 5.2 DME and GS8.55 TCU... So just need to track one of those down now, ideally with the trans loom. That'll be a lot easier than reverting to EWS III which will require modding an E46 cluster (or hiding the E39 cluster in the dash somewhere!)