Chasing my tail to find ground circuit for this chip...

[viper]

So I am working on a Ford Body Control Module.  The vehicle was in an accident and wire harness was smashed so some shorts occurred. the ECM also took a hit to the 5V power supply chip for the sensors but I was able to find and replace that chip.  Now I have issues with the BCM.  The rear hatch will not open for any reason and per the vehicle schematics, the latch relay is driven by the chip I linked.  As was my 5V ECM chip, this one seems rather well protected BUT there is some indication that reversed polarity could damage the chip so there is a diode and resistor to ground. 

I have found the chip on the BCM board and already desoldered it via hot air but the main issue is although I have found the pin on the MCU that drives the chip, I cannot find the ground at all!  As you can imagine, these boards are production, 1x use kinda thing.  Throw aways.  So they were not really meant to be repaired.  There are hundreds of vias and this is a tri-level board.  I see the ground going to a 10K resistor, then looping back to the CS-DIS and that trace pops into the center layer with a via and I have no idea where it surfaces!  I have spent hours testing everything and almost convinced at this point the trace may be burned BUT when I throw the meter in auto ohms, it seems to talk to several things from 10-100K ohms.  If the trace was really blown, would it show up somehow visually? 

I started combing the board for anything resembling a diode as I am expecting to find a diode and resistor to ground.  At this point I cannot even determine what ground is!  It is a complex critter!

[viper]

Never mind.  I found the mysterious ground.  Looking at the some traces wrong.  Hate when they make odd turns right under a component...

I am currently torn in what to do though.  components to ground are fine, input protection devices to the VN5016 are all intact, and I am not finding anything obvious on the chip to indicate it is toast. 


Does someone have an idea, in an automotive app, what might cause this chip to fail in a large network of other components and all others seem to work fine?  This chip drives the coil of a small relay that is in the fuse panel under the hood.  However, it sure looks like you could run 12V back to the chip all day without concerns.  It also handles way more than 12V.  Not too convinced yet that I have my smoking gun.