3200 gt throttle gremlins

May be of interest to 3200 owners. Over the last couple of months I have been having spurious rev counter readings showing anything between 1000 to 1500 rpm when turning the ignition on (mar position), switch off and back on and the needle is ok, also been throwing the occasional P0221 and go into limp mode, again switch off and restart and all good. Checked out the voltages to TB and TP and found all ok until last week when error code P0220 popped up resulting in total loss of throttle (idle only) and no limp mode.

After checking out again (engine hot this time) found 38 ohms of resistance on the earth wire running from the throttle body 6 pin plug to the engine earth point (102) on the front of the right cylinder head. On removing the wire from the loom there was a visible break in the outer sheath where the wire is bent 180 degrees but the actual fault was with the earth stud connection eye (which externally looked good). The eye tag is a crimped fitting covered with an internally glued shrink wrap sleeve, I found that the cable to the tag was only being held together by the sleeve glue, the actual wire was broken except for one strand.

The cable will have had a lot of weather, vibration and heat over the years which I believe has caused the copper to become fatigued and brake strand by strand until there was not enough cable left to carry the required amperage. New cable fitted and now all working perfectly.