Ecu troubles

[Bentonpclark]

Basically, I recently purchased a 2007 535i, except the ecu that's in it is for a 540i, due to this some things, like the radio don't work, is there a way I can reprogram the ecu ? Or would I have to purchase or acquire and 535i ecu. The car runs and drives with the 540i ecu and such. How would I go about fixing this issue.

[328 Power 04]

Hmm, why do you believe it has a 540i ECU?

For my clarity, what are you calling the ECU? To me ECU is engine control unit, and rarely electronic control unit.

[bmwdirtracer]

A 540i? In the USA, 2007? Um, not even close. And, as Abel asks, what are you calling an "ECU"? The radio isn't connected to anything with that acronym. Perhaps you've received bad information...from the seller?

You need to take the car to a BMW specialist shop, and ask them to diagnose the issues. The "radio" is part of a complex system which becomes inoperative is a single component is dead or disconnected.

[Bentonpclark]

It's what I was told by the seller. The locks don't work, trunk won't pop, radio screen is off. He told me they replaced the ecu. Is there ways at home I can troubleshoot this issue?

[328 Power 04]

Odd, yea the car needs a bit more diagnostic scans with a capable tool.
There are over a dozen "ecus" in your car so it would need some digging into. It's certainly possible to fix, but it would take someone very familiar with these cars' electronics.

[Bentonpclark]

I should add he has the old "ecu" in question and the car didn't want to start with it in, so they replaced it with the "540i" ecu and it runs and drives now but with those issues.

[MarcoZandrini]

Go to www.bimrs.org to find a reputable indie shop that specializes in bimmers in your area. Stop putzing around.

[pbonsalb]

It’s not the engine ECU. It is one of the other ECUs for accessories, often called modules. Sometimes they need to be programmed or coded to the car, which requires a high level scan tool most DIYers don’t have or a laptop and copy of BMW software, which some do have and which can be found relatively cheap but requires knowledge to use. And not just any module that plugs in can work — could be the later 540i module will never work in a 535i.

[328 Power 04]

I suspect that the shop threw in an entire DME (engine ECU) / CAS / Key set, with the MSD81 dme instead of the MSD80 (which were failure prone). It's not a "540i" ECU in any way shape or form. That is ridiculous and speaks of how bad that shop/seller is.

This swap would have changed everything in the car because it comes from another car with another car's VIN, etc.. It requires a lot of good programming and coding to convert all the other modules to match the data from the set of doom.

[Bentonpclark]

How should.i go about that problem? I belive thatsnthe case with the engine ecu aswell. Because there IS a new set of keys and the last were misplaced. If I had the old ecu could I fix it? could I just purchase or find another 535i ecu? Sorry I know I could just take it tona shop but I'd really much rather learn and fix the car myself. I typically do that however this "ecu" situation kinda stumped me.

[dworthy]

If you are computer savvy, look into getting ISTA+ or even INPA to talk to the car. Those 2 programs are both dealership level diagnostic programs with ISTA being the newer of the two. Either one will help you with talking to the car to see what the issues are and with ISTA, it has test plans that can help walk you thru how to fix the car.

[Bentonpclark]

Okay after some research and a little guess work. I'm assuming the MSD80 dme (wich apperently fail often) that was originally in the car had failed. And they replaced it with a MSD81 dme and Keyset wich allows the car to run and drive but didn't code or rewrite the the "new" used MSD81 dme. With that being said I had seen others had replaced the MSD80 with the MSD81 because it doesn't fail nearly as often and it's an upgrade. But how do I go about reprogramming a used MSD81 dme? I've seen that others have taken them to dealers to be reprogrammed and well. 4k seems like a really steep price for reprogramming and I'd like to take a crack at it myself if I could. Any suggestions?

[dworthy]

You will have to "write" the VIN into that DME. The other issues will come if you ever go to a dealership for a key, as the EWS part is hard coded to a specific set of keys. So if you still have the old EWS you can align it to the new to you DME using ISTA or INPA.

[Bentonpclark]

How difficult would you say that process is for someone who's never done that before? I'm very interested in learning and I'm decently computer savvy but I also just want the car fixed up as a daily

[328 Power 04]

Since the MSD81 (*still a 535i ecu*, but a new revision) works, then you would leave the ECU alone. MSD81 is better anyways. It should be checked if it contains the right data.

You would have to adapt the rest of the car to "fit" with the CAS module. That means recoding and some re-VIN-ing. When you swap a key and CAS module from another car, you essentially change that car's VIN to the new VIN.

Unfortunately, none of this is something a normal independent shop will know how to do. This is a lot of advanced stuff.

[Bentonpclark]

I believe that's the issue. Is that it's a used MSD81 from another vehicle and that's causing alot of things not to work correctly, right? If so could I just. Clone the old MSD80? If so how do I go about it. I know bmws are pretty computer friendly and you can even tune them with a phone. But I just wanna make sure I'm doing the right thing before delving into a rabbit hole. I should also mention I do have an opportunity to, get my money back in full for the bmw? What would you guys do?

[328 Power 04]

No. The MSD81 is fine..

They likely used the CAS system (vehicle security system) and key from the other car too. This is the lazy way to swap ecus.

The CAS is likely causing the trouble here. It has a different VIN that cannot be (easily) changed, and it also needs to be told of all YOUR vehicle's options, not the donor vehicle options.

The MSD81 isn't involved in much else, it isn't the main "brain".

- - - Updated - - -

This vehicle's security functions (swapping ECUs, keys, or other modules) is still strong to this day, and this will not be a job you can do via phone or even basic OBD.

There can be workarounds, such as converting the vehicle completely to the donor VIN (since it came with the CAS), and then you'd still have to make sure the actual vehicle options are programmed in and linked to the CAS.

Basically it's currently a major mess.
To solve it, you need someone very knowledgeable to work on it.

[bmwdirtracer]

And Abel's the only one I know who's that capable.