850 GLE 2.0T broken ECU?

[Daniel523753]

Hello guys!

Please help me out!

My 850 all of a sudden failed to start, after being pretty reliable for the last 2 years. I checked all the usual suspects, but traced the issue to the injectors not getting a pulse from the ECU. When I opened up the plastic box, the module itself was quite hot.

I have a spare ECU (from presumably a 2.5 manual) swapped that in, and the car started right up!

The ECU connectors all look as good as new.

I understand ECUs seldom fail, so what am I missing?!

(I would just keep using the spare ECU, but it's giving too much fuel, makes the auto transmission really rough, plus - I assume the immobilizer - shuts the car off after a few minutes )

Any insight is much appreciated!

[brickman]

Mane sure ecu cool air pipe is fitted. A few folk have had cooked ecu, especially auto cars as the tcu sits in same box and also produces heat = failed solder joints eventually

[Daniel523753]

Thanks brickman! Yeah I'm missing the pipe, but probably not the issue this time:

I managed to read both ECU eeproms, and my original .bin file is identical to a 850 GLE 2.0T file I downloaded from the internet. If I pop my original eeprom into the spare ECU (), the car still doesn't start.

So I now have to assume both ECUs work fine, but the injectors are only firing with the non-original ECU.

I'm baffled..

[Clan]

Originally Posted by Daniel523753

Thanks brickman! Yeah I'm missing the pipe, but probably not the issue this time:

I managed to read both ECU eeproms, and my original .bin file is identical to a 850 GLE 2.0T file I downloaded from the internet. If I pop my original eeprom into the spare ECU (), the car still doesn't start.

So I now have to assume both ECUs work fine, but the injectors are only firing with the non-original ECU.

I'm baffled..

you are missing the cooling pipe, this produces a cooling air flow over the ECU's

[brickman]

Yup.

Ecu issues are very very rare so you should be able to find one as a replacer that works. Not so familiar with them tbh as rare anyone ever needs one. Make sure to fit a new pipe (petrol cars cook all their plastic so try looking on a scrap diesel instead or new isn't much) otherwise your replacement ecu will also cook and die.

[Daniel523753]

Thanks guys! Yeah I'll be sure to fit a new pipe once I manage to actually resolve the issue

The situation right now is:

- the car starts up with a '94 850 T5 ECU program if I load it into the eeprom, the injectors are firing properly
- the car does not start up with the original ECU program, the injectors are not firing

I have double checked the fuel pressure, +12V on the injectors, crank sensor, speed sensor, TPS signal, ECT signal, all the grounds.. The ECU is just not pulling the injectors to the ground with the original program..

What am I missing here?

Could it be an immobilizer issue, where the immo blocks the injectors for some reason? (I replaced the dash about 2 months ago, but I've been using the car with the replacement happily ever since.)

[Goupil]

You could try flashing an american map if you can find one (M4.4 are easily available, not sure about M4.3) as they didnt get the immo before 1999

[Daniel523753]

Thanks Goupil! Yes, I checked now and my spare ECU .bin has a date code of 071093. I believe even European cars did not have immo at that time, so that could be why the car is starting up with that ecu, as it just ignores the missing immo signal.

I'll be checking the chip in the key and the immo antenna next!

[Daniel523753]

Solved!

The car is running fine with a slightly older ECU program (that is apparently not checking for the immo OK signal).

I tried replacing the immo 2 box, antenna, and checked the wiring between the immo box and ecu, but all of those are fine, so it would seem to me that the ECU itself fails to communicate with the immo box for some reason.

What I've learned:
- you can hack an immo off solution by finding an older ECU program, just make sure that all the maps match (MotronicSuite helped me with that)
- the automatic transmission seems to be controlled not by the ECU program, but some other logic inside the ECU box
- having the snorkel for the ECU is probably a good idea, especially for automatic cars as some of you have suggested

Thanks for all the tips!