My 1991 honda accord is showing the code of 8 which is the tdc. Where is it located and what exactly does it do? And how can we fix it

It's located inside the distributor and it's unserviceable. Buy a genuine Honda distributor housing and install your present igniter and coil--aftermarket brands are not reliable.

I believe it's integral to the distributor and your resistance reading to the ECU is out of tolerance. Aftermarket replacement is a crap shoot.