In a service news article from Honda they say the following:


Tach Fluctuation and/OR A/T
DTC P0725: Accord V6

On 1995-97 Accord V6s, when you troubleshoot a fluctuating tachometer OR A/T DTC P0725 (lock-up clutch does not engage), keep in mind the cause could be a faulty resistor in the ignition coil. The transmission control module (TCM) provides electrical pulses through this resistor to drive the tachometer. Although a faulty resistor doesn’t affect the coil's ignition functions, you'll still need to replace the ignition coil to fix a fluctuating tachometer OR A/T DTC P0725 the coil resistor isn't available separately. Order P/N 30520-P0G-A02, for the ignition coil.

We had this happen on a couple of cars in work and replacing the coil fixed the problem.