93-95 GM 3.4 OHV tach signal strength?

[limey222]

can anyone tell me what is the correct signal strength for the tach signal coming out of a standard PCM for this engine?
I assume it can be measured on a volt meter set to AC.  Mine seems too low for even a Dakota Digital black box to amplify high enough to activate a VDO tach.

[Scott Costanzo]

I believe it is a 5 volt square wave.

[Charles]

I have VDO gauges, so when I tried to use the output from the coil pack I could only get 0.4 Volts. The guys at VDO said 4.0 V was min. I now use one of the phases from the alternator. Vdo has the setup to use the alternator. I have 3.4l V6 GM.

[limey222]

my PCM tach feed in the BMC harness is only putting out 0.35 volts so i will have to go with the aleternator signal route.