What is error code 07511 a 1997 Chevrolet truck

P0751 means Shift Solenoid A Performance or Stuck Off. Which means ur transmission probably is not shifting correctly due to bad or stuck solenoid

P0751 CHEVROLET - 1-2 Shift Solenoid Stuck Off...Possible causes; Low transmission fluid level, Dirty transmission fluid, Faulty 1-2 Shift Solenoid valve, 1-2 Shift Solenoid valve harness or connectors, 1-2 Shift Solenoid valve circuit is open or shorted...When the a transmission solenoid is stuck off, 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.