what was the PCB not doing- was it the lack of a pulsed fuel pump output- or did the diagnostics go into that level of detail?
as an aside- found this thread so the problem doesnt appear to be confined to car based units
http://www.ybw.com/forums/showflat.p...fpart/all/vc/1
It looks very much to me like a power mosfet and given its location on the board suspect it is used to drive the fuel pump via the 6 pin connector.
If we could identify a part number it would be worth having a go at changing one on a duff PCB ( assuming this route hasnt been gone down already)- I have SMT rework facilities