been chasing a gearbox issue....

[britlude]

for quite some time i've been getting an occasional gearbox 'glitch'.....

every now and then, it decided to move the shift points of the gearbox up, and not be completely happy, til the car was switched off and restarted.... if it happened an off/restart cycle meant the gearbox continued as if nothing had happened! no 'down time' needed, instant restart cured it.. def hints at electrical, rather than mechanical/hydraulic...

connecting the test point to get the blinky/flash dash indicators showed nothing.....

as i had another spare gearbox ecu (actually got 2 spare!) I swapped that in, but it eventually showed the same issue! hmm not that then!

i was going to ask on here or Prime, but as the usual advice is 'put in a manual' or 'it's not a proper NSX', i didn't bother!

eventually i did it again, and this time i thought to check the diagnostics with the engine still running... sure enough we have a fault code! hurrah! 3 lovely flashes!

this points to the gearbox ecu losing the throttle position signal (permanently or momentarily makes no difference, once it's lost, it defaults to lost until it's reset!)

this tallies up with what i see at the fault condition, the computer moves up the shift points as it doesn't know what the throttle level is, and loses kick-down and torque converter lockup!

so now i know it's the red/yellow wire, i checked as per the manual, levels where expected,changing with the throttle position, disappearing when the throttle pot is disconnected so i know i have the right wire......

connections checked and cycled, trying to replicate any loose connection, alas no

on the way to goodwood we had to brake on a particularly rough surface at some traffic lights.. after that the gearbox was not happy... again 3 flashes in the OBD test condition.....

moving away from the ecu, tracing the wiring loom, i find the connectors between the engine loom, and the 'floor' loom.... mounted on a weak mount and in fresh air behind the drivers seat.... hmmm that could be subject to vibration.... so the connectors oiled and cycled a few times, and then supported with some foam.....

fingers crossed!

IMG_20180715_115421 by jon sutherland, on Flickr