M52b28 Hard 5500 Redline and P0600

[Steez30]

Recently completed a M52 Swap in my 1989 E30 previously 325is.

Swap went very smoothly and I thought all was well while driving but i noticed that when i drive the car, the first time i do a pull it will allow me to reach the 7200 redline as coded. but the second, Third, and so on time i try and pull no matter the conditions it has poor acceleration and a 5500 firm redline.

Its as if when the car is cold I can redline at the expected levels and once the car reaches temperature it wont allow it anymore.

Throwing 11 codes as of now 6 present and 5 pending

They are as follows


(x2) P0443- Evap Emission system Purge control valve circuit

Explanation: SAP not found (should have been deleted)



(x2) P0141-o2 sensor heater circuit bank 1 sensor 2

Explanation: (post cat o2, should have been deleted)




(x2) P0600- Serial Communication Link (CRITICAL)

Explanation: TCU not found? or something else




(x2) P0111-Intake Air temp Sensor 1 circuit Range/ Performance

Explanation: Air temp Gauge that is in rubber boot sending bad signal (replaced and no code anymore)



P1421-Manufacturer Control

Explanation:This code indicates a problem with your secondary air system. SAP Pump
(Should have been coded out)




P1423-Manufacturer control

Explanation: This code indicates a problem with your secondary air system. SAP pump
(should have been coded out)



P1145-Manufacturerer Control

Explanation: field tank vent (Evap should have been coded out)

As stated in most of these codes they should have been removed from the ecu entirely by the tuner who removed ews from my DME. However there are still checks being run for them. only one that "causes limp mode" is the P0600. Has anyone delt with this and what was the fix?

In all seriousness if someone actually helps me fix this I will give you a 3d printed e30 lol

[Northern]

very rusty with MS41, but there's some difference between auto and manual - does it think it's auto?

I think the codes for SAP, Post-cat O2, evap, etc. need to be suppressed in the tune as well as the functionality disabled via the control bits, maybe the tuner only did the first half? or not at all...

About the lack of info with some of those codes... this isn't going to fix anything, but should reduce the ambiguity of the "Manufacturer control" stuff:

If you can convert the OBD2 Poo codes into bmw DTC codes, there's a DTC list here:

https://sites.google.com/site/openms41/reverse-engineering/documentation/diagnostic-trouble-codes-dtc

Or in 2026 you can just throw the Poo code in bmwfault.codes (Made by Matt P of this forum and e30tech... can't remember his username):

https://bmwfault.codes/

[Steez30]

Thanks for the Info Northern,

What was requested of the tuner was
-EWS Flash
-Post Cat o2 Delete
-Evap Delete
-Redline Increase
-Manual Code conversion (Ecu is from Automatic donor car)

would it still throw codes if those were deleted. and it does seem like the P0600 code refers to the ECU trying to Connect with the TCU and not being able to. Could I re-tune everything and try to fix those errors?

[Northern]

I can't remember if the auto to manual stuff is just a control bits change or if it's a different flash between auto and manual. I have a few MS41 but all of them are from manual cars.

The redline could also be from VSS, 5500rpm sounds correct for that at least.
Basically two issues -
Major: If VSS isn't hooked up to the ECU, it'll error out and limit to 5500RPM.
Minor: Since the E36 uses the 48 tooth ABS signal for vehicle speed, e30 uses the 9 tooth diff sensor, the signal it receives is way too slow, and may trigger that same error at some point. I think most people never have this issue, a few encounter it at some point.

Hooking up the VSS signal is reasonably easy, but some E30s have it through the C101-X20 adapter, and some have it through the connector in the glovebox (C104?)
VSS factor is correctable in the tune, there's a thread buried in the romraider forum about it the factor.

This won't fix your other codes, BUT it might fix your limiter (unless the TCU code also triggers it)
Some of these codes may not trigger a CEL, so maybe they aren't a problem for you.

I'd probably double check this first though.

[DesertBMW]

who ever tuned your MS41 just did EWS delete and nothing else.

[Steez30]

I thought my VSS was set up correctly since i have a late model e30, however upon viewing the x20 plug where my signal should be flowing through I noticed that the pin is not there. Apparently on the automatic engine harness the vss goes through the egs which is a different connector that was cut off since its not entirely needed? so that could be the issue, but still not ruling out that the guy who tuned my ECU did it entirely wrong. Does anyone know anyone that tunes these/ would verify mine was done right?

[Northern]

I'm not sure who the go-to people are these days.
The tune can be read-locked, but if he really had no idea what he was doing, then I doubt he could/would do this.