Don't you just love those kind of problems. I will put that one in the memory banks just in case. Glad you got it going!!

Finally got the problem figured out,Wire 10G in the control handle was rubbed thru with another wire and causing all my issues,was causing the capacitors to drain on key off and for lift to function also. new harness for control handle on its way,and should retrain the operator,he thinks hes driving in NASCAR and has to operate the control handle like a stick shift.....

A code -51 will come up on start up if there is an accessory like a scale or something running straight off of the battery power. It can draw the power out of the capacitor before your line contactor has a chance to pull in. You have to have a direct short brom battery positive to the control card, powering up the card only so the display is working and it thinks you are requsting a startup. You need to check wires and connections for a direct short to the battery. I can get you some wire numbers to look at if you want. I agree with checking battery voltage to the frame with the battery in the truck and then out of the truck.

with battery plugged in shows -51,unplugging key switch no change,turn key on and truck powersw up normally and drives and lifts and has aux functions turn key off and -51 comes back on display and dosent go out am thinking there is something draining the capacitors with the key off,possible pump motor,wire 61 from pump contactor from what i see on wire diagram,going to check more today

code: -51
from my recollection
this can be caused by a couple of things
-battery cables too long
-Tag lines without filters are being used (doubt this is it but the manual lists this as a cause)
- High peak current in motor, possible shorted field windings or shorted armature winding.

even though these troubleshooting suggestions are just that and you most likly will not find anything wrong there, i do see it shows the current sensor in the troubleshooting diagram. Have you checked this? Check the motor itself for grounds to the frame from positive and negative both. It could be picking up residual induction through the motors and causing the "shorted" effect, would explain why it blew the control fuse on keyswitch.

Try pulling the battery out of the truck, see if the code goes away(case bleed through can cause issues)
blow out the motors, carbon dust can cause havok as well if the insulation in the motors are breaking down.

so you have some reaction on the system with key off? AND with it ON as well? just flipflops back and forth?
what happens when you remove the key from the equasion? plug in the battery?

almost sounding to me like you have a control wire shorted/melted against something, this would explain the blown fuse and the strange readings your getting on the keyswitch.

Just some things to ponder while running around in circles ;o)

Guess i should verify what machine does and what i've done

With key off just as soon as you plug battery in to truck code -51 comes on dash display and wont go out.Truck will lift and lower(No auxillary functions tho) As soon as you turn the key on,display goes to battery state of charge and truck seems to operate normally,until you turn the key off then goes back to -51 code on display and lift/lower functions work.
Have had EV5TPS control card checked by flight systems,replaced keyswitch and steer interlock switch on the line contactor.
One thing i did find today while checking is the wiring to the key switch,both connectors have battery + voltage(36V) to them with the key off?

Have you checked for earth faults or shorts on the traction motor?

In looking at the schematic I would think that the steer lock switch is causing your problem. The switch send positive to the solenoid card which would allow the hydraulic functions to work with the key off. You could pull the #10 off the switch to test. It is possible for something else to back feed it

Still no luck finding whats wrong with this truck,had the EV-5TPS control sent out and tested/rebuilt,still throws a -51 code with the key off and has lift function with key off. Steer interlock switch and line contactor being put in tomorrow,see if this cures it am at a loss as to what it is after this.

Does this help?

POSSIBLE CAUSE
*Defective capacitor.
- Check capacitor bank per component checking section.
- Check for loose or open connections in capacitor circuit.
*Misadjusted / defective steer interlock switch.
- Check to insure that the steer interlock switch closes after
the line contactoh power tips close. Repair or replace. -Defective steer control.
- Disconnect the positive cable and 4PL plug from the steer control. If status code disappears, repair steer control.
-Open circuit in capacitor precharge circuit.
- Check for loose connection or broken wire (WHT) at #3 REC
heat sink or along the length of the wire.
- Check for loose or corroded connection at terminal PZ14.
- Check for loose connection or broken wire (BLACK) at 1FU
power fuse or along the length of the wire.
- Check for loose or corroded connection at terminal PBl.
*Unsuppressed voltage spikes.
- Check that any and all coils, including horns, that are
present on the truck have the proper voltage suppression. - Check that the static drag chain is present on the truck and
dragging on the floor so that it keeps static electricity from building up in the truck.

Serial Number: NPR345-0203-9700 It has a EV-T5PS control and also has the oscilator card that looks like an ev100 MX/ZX card with the A,B Y,Z plugs

how about either a serial number series, or which controller is fitted, so we know more about the possibilities for the code? my bet is in the plug connector, as long as the motor is known to be good.

No one with any thoughts on this issue??