tach not working. strange findings....

[joshpntbl07]

well, i just got a 95 240sx with the ka24de in it. the tach didnt work when i got it so ive been trying to diagnose the problem today. useing a fsm ive checked voltages at a couple different places.

while the car is running im getting around 6 volts at idle at pin f3 of the ecm. and it does rise as i rev the car. the fsm says i should get around .9 volts at idle.

at pin 21 of the instrument cluster im getting 0 volts. the fsm said i should have battery voltage there. i guess that means 12v. i ran a wire straight from the battery just to see if that fixed it, but no luck.

i checked voltage between pin 22 and 12 while car is running. i think there was -.6 volts and it did rise with revs. im sure that cant be right.

im not sure what to make of it. i bought the car from a buddy and he told me that the original owner had a r33 motor at one time. maybe he had to rewire some things so the tach would work with that motor, but the harnesses for the cluster seems untouched. any help would be great. thanks for reading

josh

[joshpntbl07]

i ran a wire from pin 3 of the ecu to pin 12 of the cluster, grounded pin 22 on cluster and still nothing. just a quick blip right when i crank the car and then nothing. i have tried a different cluster also.

where does the ecu get the signal from? im guessing the dizzy harness, but which wire?
Modified by joshpntbl07 at 2:22 PM 2/28/2010