Possible causes

– Low transmission fluid level
– Dirty transmission fluid
– Faulty line pressure solenoid ‘B’ valve
– Line pressure solenoid ‘B’ valve harness is open or shorted
– Line pressure solenoid ‘B’ valve circuit poor electrical connection

Tech notes

When the a transmission solenoid is stuck on, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is very dirty, it is recommend changing the transmission fluid and if possible removing the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a transmission mechanical failure and that the transmission will need to be rebuilt or replaced.

When is the code detected?

The gear required by the Engine Control Module (ECM) does not match the actual gear when driving

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Transmission shift shock

P0777 CHEVROLET Description

The line pressure solenoid ‘B’ valve regulates the oil pump discharge pressure to suit the driving condition in response to a signal sent from the Transmission Control Module (TCM).

CHEVROLET Technical Service Bulletins for P0777 code