ECU up the creek

[matina]

My e46 328ci is diffucult to start, but once it does start, the car cuts out after half hour or so.

BMW plugged their thing in, and said open circuit fault code P1622,

open circuit on the map cooling circuit.

Diagnostic guy said the same thing, but mentioned the ecu may be faulty.

would this be a phyisical fault or would it require a software flash?

I cant start the car and wanted to know if anyone knows of (cheap) BMW electrical specialists in the london/surrounding areas

hate the car. want it gone!!! will fix it if the ecu thing isnt too bad.

Thanks

[< FORZA WEST]

Unusual, the map coolant curcuit usually has no effect on the engine only on running tempurature.If the fault is in the DME and has been diagnosed as an open circuit then its a physical fault and will require the DME.

Cant say I've had that one as a cause of none start and cut out.That normally tends to be the blue relay next to the DME cutting the power supply.The contacts burn and become weak - worth checking it out first!!!
The other one is the fuel pump.

[matina]

Thank you!!!

i changed the fuel pump relay and another two of them. When i fitted the new thermostat/sensor unit, the car drove perfectly normal for about 1 mintue. possibly as it didnt have time to register the fault as they had been cleared once fitted.

If you confident its the ECU, then do you know of anywhere where I can get hold of one and have it reflashed or rebuilt?

[Pork_n_Beem]

FAB Recycling Ltd is very good, 01594 827333.

Parts are posted as they are in cinderford

[matina]

Could a short circuit in the loom throw up the same code?

The diagnostic specialist mentioned the ECU was constantly sending a signal to the map sensor but not getting anything back.

Am i right in thinking, the DME is constantly sending a signal as opposed to once a minute for example, so it can then mess around with the fan and thermostat to regulate tempretures?

I may have sourced a loom quite cheap, admitedly used but warranted so may proceed with that first, as BMW quoted me 700 pounds for a remanufactured ECU
and 200 plus for a loom.

Is it hard to change to loom? i know its plugged into sensors, but their physical access, it is hard to get to and have to strip ancillaries to get at them?

[< FORZA WEST]

The OPEN curcuit can be a break anywhere from the sensor to the DME.It would be better to trace the fault and repair than to guess and replace-very expensive way to proceed.If a wire is cut it will take minutes to find with a multi meter and pence to repair + you prove where the fault is.

I disconnected a map thermstat today and it has no effect on the starting or running of the engine!

Is it the only fault listed?has the induction pipe to the throttle been checked for cracks?Is it the coolant temperature sensor that flagging the fault.Its under inlet manifold,if that has failed then it has an effect.Are you able to have the DME checked to see what temperature the coolant is at...ie -40'c.

[matina]

Thanks for the tips.

Had the car plugged into my laptop with live readings of the O2 sensors, maf, coolant temp, TPS etc and they seemed fine. temp was registering 84 degree celcius until it cut out.

The diagnostic specialist, changed a vacum pipe to the inlet and made no mention of the intake being faulty/cracked etc.

i also sprayed carb cleaner on it whilst running to make sure there was no change in revs un-metered air.

My issue lay with the car not starting and it potentially cutting out to run the mile or so to the garage.

I just cant trust it anymore. When BMW plugged their diagnostic in, the only fault stored was the P1622 code, open circuit.

But having said that, perhaps, a last ditch attempt to let the guy play with it is the only way to sort it. the car owes me loads of money as it is, but i can budget another 500 for diagnosis and repair.

if its something big like the ECU. ill have to call it quits and take a hit.

No one can get past the EWS3 on these ECU's...and BMW only enjoy selling you a remanufacturered one.

With regards the temp sensor, how would that affect the car? As the car registers 84 degrees, do you think, it maybe throwing an errant code back to the ECU? Highly unlikely i would imagine, but what effect would that have on the car starting and cutting out.

Thanks for your advice. At last, someone who knows these E46's.

[< FORZA WEST]

The DME reads the coolant temperature, if the coolant was being seen as +80 degrees when really it was 4 degrees then you would potentially loose cold start.But one I have seen before is the coolant sensor was sending a signal of -40 so the dme puts in maximum fuel which floods the cylinder and so on.

Another problem we used to see was the MDK motor (throttle body),although cable operated they have a motor driven butterfly.The butterfly would stick.

How old is it? on the later drive by wire we have issues with the connector to the EDK motor.

[matina]

The car is a November 1999 model. Everything is buried under the manifold. I cant see a physical throttle cable. I cant get the manifold off, due to the rear retaining nut.

Regards the temps. when i had it on my laptop, the car was registering 84 degrees, its also the same with BMW's print out when running the diagnostic.

Im at a loss, as to why this car is doing what its doing.

I couldnt persuade you to have a look at the car?

Or i can somehow drag it down to you. assuming it doesnt cut out somewhere dangerous and inconvenient, like it normally likes to.