Graco Reactor E-XP1 Troubleshooting Manual page 30

Reactor Error Code Trouble Shooting Guide
 Check the analog gauges to see which pressure is higher. And then check
 With the pump still off, use the pressure relief/spray valve to slowly
Rev 2.6 (02/2014)
and see if the pump display pressure matches. If it does, that would
indicate that the motor control board is "Seeing" that transducer.
relieve the "higher" side pressure, while watching the digital display and
the analog gauges. Once the higher analog gauge drops below the lower
analog pressure the pump display should start reading the "new" higher
side pressure (because it is now the higher of the two). Then slowly drop
the "new" higher side pressure until the digital display stops at the original
"higher" side analog gauge reading.
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