4R70W MLPS Testing

Does anyone have/know a way to test the MLPS?

Problem: Will not shift out of 2nd gear.

1996 F150, 4R70W, 5.0L ~129K/mi.

I prefer to test mlps rather than just replace w/o knowing if it is bad.
I understand a corroded(s) ground will also affect MLPS, but where the hey are they?

Thanks for any info,
Gumby_CT

When testing this switch you need a volt- ohm meter. Set the volt meter to D.C. volts. The most common way of testing this switch is while the engine is off, but the ignition is on, place the ground lead of the volt meter to a good vehicle ground. Looking in your service manual to locate the drive wire coming from the vehicle, going to the inhibition switch. Place the gear selector into drive and check voltage going to the switch. If there is no voltage going to the switch, that must be diagnosed first.
Probe both the incoming wire and the drive wire leaving the switch. If you have no power leaving the switch, the switch is improperly adjusted, or is defective and must be replaced. Another test to check the switch assembly is while you have the vehicle on and selector is in drive, probe the P-R-N-0-2-1 wires and check for voltage at these. If you have any voltage coming across any of the wires coming out of the switch while selector is in drive, the switch is defective and must be replaced. Hope this helps and good luck!