96 tach reading wrong

we have a 96 thunderbird and the tach just deicded to be lazy. at 65mph its reading 1 not sure were to begin. can anyone point me in the direction? i check connections to the coils they were clean and connected. thanks!!

Are all of the other gauges reading correctly and indicator lights in the dash working? The signal for the tach comes from the PCM so see if any codes are stored that might give you a clue. Go to my post in the second page of the Tech help thread to see how to get the schematic and other info on-line.

thanks ill try that!