WTF? on the ECU - BMW Forum

FearsOfWar · 07-07-2009, 11:21 AM

So I had a problem traced to my computer, and had the whole thing replaced. We bought a used computer (housing and everything, not just the chip), and had it replaced.

Well, I've noticed a small loss in 5th gear power, the AC doesn't blow out as cold as it used to, and the cluster gas gauge, nor the on board computer gas range works.

Everything else is exactly the same.

I opened up the glove box and checked. All the numbers match exactly, my only concern is someone took a paint marker and wrote "1985 528e" on it. I have a 1986 325e, so I know it came off a computer around the same time, so I would believe they are interchangeable without this level of difficulty.

Anyone know anything that might be the cause, or have any ideas?

romeomike · 07-08-2009, 09:47 AM

http://www.wedophones.com/Manuals/BM...g%20Manual.pdf

With higher heat and humidity, AC performance will suffer. My vent temperatures are 15 degrees higher (from 40 to 55), but when it's 108 outside I can understand it.

With the ETM, you'll have the schematics for the OBC and instrument cluster. Prayerfully it's nothing more than a fuse. Diagram attached.

You can compare your ECU's Bosch part number against this list:

list of all BMW ECU's (long)

FearsOfWar · 07-08-2009, 11:03 AM

When I took it into the shop, the AC worked fine, the cluster gauge worked fine, and the on board worked fine.

On the way back from the shop (it took all of 20 minutes to swap), the AC no longer worked right, the gauge, and computer didn't either.

It was almost like it instantly stopped working with the computer swap.

The computer part number was the same on both the old & new computer.

romeomike · 07-08-2009, 11:43 AM

Did they undo your negative battery cable prior to going into your glovebox to change out the ECU? If they did, the computer lost its settings for date, time, average mpg, and average mph. If they didn't, there's a possibility a fuse blew during the ECU swap.

You'll have to be more specific when you say the AC no longer worked right. My assumption was overall cooling performance deteriorated, but you could be having problems with your blower fan. Both are fuse-protected.

The OBC depends on the fuel gauge input to determine how much fuel is left in your gas tank. So if the fuel gauge is not working, it makes sense the range calculations would be off.

Invest in a digital multimeter if you don't have one already and do a continuity check on the fuses suggested by the diagram I attached earlier.

FearsOfWar · 07-11-2009, 12:48 PM

I just had a thought.

Can an aftermarket chip pull up an error when the ECU is checked for problems?

ADynamo09 · 09-06-2011, 02:25 PM

To FearsOfWar, I am currently tracing down an idle issue in my car whenever it rains heavily. I believe it's the DME getting submerged in water in the chamber where the DME is located. I however, do not know where the DME is located. Could you please instruct me to the location of the DME chamber? Much thanks.