BMW 320D e46 intermittent no start ecu problem.

**AudiS4** · 31st December, 2015, 02:59 AM

Hello guys,

I am looking for some information that hpefully somone here might have.I am trying to help my sister out.She lives in england and I live in USA.She purchased a 2003 bmw e46 320d recently.She says on cold days car will crank but not start.I was told by her husband that if he removes the ecu from the car and heats it up and reinstalls it car starts and runs fine.Now from the reserach ive done this is a common problem on bosch ecu part number 0281 010 565.Apparently this is common.Does anyone know what exactly happens and what needs to be fixed??I am looking for broken traces and possible solder bridges but havent found any substantial.Any help would be great.Maybe a picture or location of where I should be looking???

Also coolant temp Needle goes into the red and all the lights come on.

**CustomCars** · 31st December, 2015, 11:20 AM

Hmmm in this case possible heating effect on volume of metal, including solder.
But problem can be with some cable or ECU adapter, for taking out is touched... so can give effect.

If want try repair ecu must try resolder Flash, drivers, MCU,
maybe problem with some capacitor too. No one say you exactly what element can have problem. After many years possible some solder crack.

**AudiS4** · 31st December, 2015, 01:24 PM

This is what I am hoping I looked at all the solder joints I found a few areas that look a bit suspicious but nothing definite.The ecru has 3 large capacitors round and orange in color.I was thinking of re flowing the whole ecu by putting it into a oven at 300 degrees Fahrenheit for 5-8 minutes but I am concerned with the capacitors and the plastic connectors on the ecu will get damaged or explode.I don't want to damage the ecu but I would think reflow would be the best way??i just don't know if the capacitors will be ok and the connectors???

**AudiS4** · 31st December, 2015, 11:45 PM

Anyone know what I should be looking for???

**auto421** · 3rd January, 2016, 08:38 PM

you have short circuit to - or positive i tink to - ,you have dignostic scanner,and post dtc in forum i can help you
best regards

**auto421** · 3rd January, 2016, 08:43 PM

i tink hife you rebaling processador (mcu)very fluid amd and air hot .very carreful in air hot 260c? to max.
try and post results best regards

**AudiS4** · 3rd January, 2016, 10:48 PM

I dont have the ecu in my possesion anymore ecu i back in derbyshire.I am in USA.Faults Stored are:

C0700
P0848
C0317

I hear that this is a common problem.

Very common ECU problem causing non start of the engine intermittently, when the fault occurs you will notice that the engine management light does not come on and the temp guage will go straight into the red. If you are using diagnostic equipment to read the fault codes you will also notice that when the ECU fails you will not be able to communicate with it.