What causes code 81 on 94 gmc serria replaced lock up sol shift sol an epc sol still reading code 81

Did you clean the cooler lines? 200 is to hot. 1811. Pull the side cover of the transmission and replace the EPC solenoid and both shift solenoids. Watch the check balls. Make sure they go back where they came from. After this you have to reset shift adapts. Takes a scanner.

controls the shift points. its on the transmission. check wiring to EPC, if ok, then replace EPC solinoid. ( The electronic pressure control ). Good-Day!

Sounds like the key switch has failed. Either the switch or the linkage between the switch and the lock cylinder.

My friend this sounds like a catalytic converter problem. A number one symptom in the case of a "burned up" catalyst is loss of power or as you put it bogged down. Try disconnecting at the flange if not too much trouble or simply remove the O2 sensor downstream and see if pressure changes (old trick)

CODE P1746 - EPC SOLENOID CIRCUIT MALFUNCTION. WHEN THIS CODE APPEARS THE ENGINE STARTED VECHICLE IN GEAR AND THE PCM DETECTED THE ELECTRONIC PRESSURE CONTROL EPC SOLENOID CIRCUIT INDICATED OPEN THIS FAULT CAN CAUSE HARSH ENGAGEMENTS AND SHIFTS. EPC MEAN ELECTRONIC PRESSURE SOLENOID.

p1745 - Transmission system problems.

The code for this concern is related to the EPC solenoid in the transaxle.

P1745 EPC EPC solenoid circuit failure EPC solenoid, circuit or PCM shorted or open. Soft/harsh shift feel

The wire to the EPC solenoid is a yellow and violet wire.The code indicates that the problem is strictly caused by this solenoid circuit. I would suggest inspecting this wire from the trans to the PCM.If there are no obvious faults, replace the wire with a new wire ,eliminating the faulty circuit. Hope this helped you.

Sounds like the clutch is starting to go out, my Sierra did the same thing between 3rd and 4th. Time to get the tranny overhauled or replaced.

transmission is shot clutches are worn out

more than likely the actuator has gone bad or just the switch

replace shift sensors under tranny pan their about $20 a piece. it worked for me you can even buy corvette sensors for it.