The unit below was changed to a new unit : 11241.
I went home to the customer, checked everything and installed the new ECU and the car started up and ran fine.
However, after I had left he started up the car again to run i warm to tighten the headbults.
After about 15min the engine died.
He says he heard the fuelpump go out before the engine died.
He tried starting again, he says he heard the fuelpump come on one time, then nothing. No spark, no fuel.
All supplys and grounds where checked and all fuses. Still no start.
I have now tested the unit on my bench and it is completely dead.
No response from CPU, not even with power from AVR.
- sounds like high voltage (probably spark) related damage
The fist unit (the one talked about below) was damaged in the same car, but the suspected culprit was a faulty cracked coil, sparks where flying at the base of the connector.
All the coils where changed and checked before the new unit went in. Still the new unit stopt working after just about 20 min?!
What are we supposed to do now? What can cause this type of damage? The engine ran perfectly, not a hiccup. Then just died.
- I can think of only ignition spark going to the wrong place (or lightning) that could do such thing...
- The other inputs and outputs should not normally suffer such shock beyond their normal protection
- We've heard of a similar case (few years ago), when the coil secondary GND-return was not connected ( the ECU is involved in the spark path that way, which most likely causes damage in short time )
Cant really try a third unit before we know what causes this?
Im out of ideas of what could kill the CPU like this?
The install is on a BMW M50, In a E36, custom electric system.
With Twinshield harness, high Z, and OEM BMW M50 passive coils.
- can you detail the connection of the passive igncoils ?
- Maybe the coils have ground return on the secondary, some of which (or all) were not grounded ?
- Dave : that could very well be it, in stock loom they are grounded on the head (near the spark plugs)
- yes the coils have secondary gnd return that needs to be connected (1993 BMW 318i - 318is - 325i - 325is Electrical Troubleshooting Manual.pdf page #97, even more clear on page #104 )
Old post from October
I have a unit that after a possible fault in wiring show strange symptoms. The voltage in VEMStune is about 9 volt, but I have 12 volt on the supply pin.
Also, one injector output, connected to fuel pump relay started to ground continuously on power on.
I have measured the transistor and there is no short, the transistor seems fine. The problem must be from the CPU?
- The injector FETs are driven by SOIC8 [FETdrivers] (TC4426 or MC33151D). The FETdriver is primary suspect in this case.
We did noting when a got a NEW unit that one ignition coil were cracked and the spark did exit just by the connector. It is possible the spark can have entered the signal wire to the IGBT
On this picture, by the pen, is that some form of 12v regulator/stabilizer?
- MC33269-DT5 (5V regulator in DPAK package)
- Could this be damaged?
- if 5V can be measured on it's output (big pad), than it's likely operational
Is there something I could check or is it better to send this unit in for service?
- The main +5V (and others, like on EC36/pin28) should be easy to verify
- also check that there are enough available non-damaged, operational FET and IGBT outputs.