Ok so...recently i had taken the rear valve cover off my 03 Honda accord with the V6 to adjust the valves. Once i got them all adjusted i went and wiped out the throttle body and reassembled everything. Now before i took anything apart to get the valves the car ran fine with no issues or hiccups. When i gone to start the car to test out the valve job it ran for like a few minutes then my dash lit up like a Christmas tree. the Check engine light started blinking, the D light started blinking, the TSC and ABS light tuned on, and the green immobilizer light started flashing and i smelt a strong burnt plastic. I went to hook up my scanner tool and it showed no connection, so i looked under the dash at the fuses and noticed the ACG fuse was burnt but none of the fuses under the hood was burnt. I did some looking up and seen it was the alternator fuse which there was some info of the alternator shorting out the ECU too so i pulled that out and sure enough there was a nice crispy spot burnt out in the board. So i went and checked out all of the components that were on the ACG circuit to see what could have possibly caused the fuse to blow and burn the ECU and found the ignition switch, alternator, ELD, and the throttle body were all on that circuit. Tracing back to all i messed with when i adjusted the valves was the throttle body when i moved the flap inside to clean out any carbon beyond that nothing else was messed with which sure enough when i tested out the throttle body it had several dead spots when i moved the flap with a multimeter connected to the last two pins. So i replace the throttle body as well as the alternator knowing it was part of the main circuit as well as popped in another ECU which my scan tool allowed me to reprogram the immobilizer to work with the swiped ECU and clear the codes. The car ran fine and i even took it for a long drive with no real issues, so i parked it and came back later to head off somewhere and after i started the car and it ran for a little warming up the Christmas tree situation came back with all those light happing as described before so i went down under the dash but this time the fuse for the fuel pump popped and i burnt out another ECU.....I know this was a story but i wanted to make clear of all the things i had done as well as figured out so figuring this out would make it easier. Any help would make fixing this quicker.

 

Seems like you forgot a ground or pinched the harness under a valve cover or intake manifold.

 

All wiring is closed up in a plastic holder that bolts on to the top of the valve cover when all assembled. The plastic is a hard ABS type and i only pulled up on it slightly to pull the valve cover out to see all the valve adjustment screws. As far as the fuel injector wiring harness thats in deep beside the injectors on whats technically the left side of the holes that the top intake manifold sits on so they are nowhere close to the edges of where the valve cover sits. No other wires or harnesses are close to that location that could have been trapped when placing the cover back on which if i think right, the issues happens after the cars temperature starts to rise so id figure if it was a wire pinch or short it would have popped the fuse and fried the ECU as soon as i turned the key.

 

Hi, did you figure this out? I am having the exact problem after changing valve cover gaskets and can’t track it down. Thanks for any info!

 

My case ended up being that the covering on the knock sensor wiring was stripped which apparently i once had mice nesting under the intake runners. In other words the knock sensor communicates directly to the ECU and each time the wire touched anything it shorted out the ECU. Sadly my situation was a freak occurrence due to animals.