Measure the three voltages on the map sensor. One must have 5.0 volts. The ground wire will have close to 0.2 volts. The third one relates to this code. It should have roughly between 0.5 and 4.5 volts depending on intake manifold vacuum. The only way for it to go to 5.0 volts and set this code is if the ground wire is open, (it will measure 5.0 volts), the sensor is defective, (the ground will have the proper 0.2 volts but the signal wire will have 5.0 volts), or the signal wire is open, (all three voltages will be correct at the sensor).