Yeah do filters first, but that light comes on when the pressure is very low. After that, do pressure checks. You should have about 200 psi at the DR receptacle just above the hydro charge filter at full throttle. Put the trans in neutral and check this pressure at full forward and reverse as well. Also check your stall pressure at the hydro motor next to the trans. There's a forward and reverse DR opposite the face where the lines bolt to. You want at least 6000psi here, 6500 would be good.