2013 Scrambler 850xp TPS wiring screw up

[JacobSlabach]

Hey just picked up another scrambler 850 was told the tps was bad.  This atv has been beet to hell.  Wiring has been tinkered with the crankcase has been replaced recently and the motor rebuilt (can see horizontal scores thru spark plug hole where it’s just been honed out and rebuilt)

my guess is it was ragged out till the motor blew a rod and rebuilt but the clown that did it couldn’t get it to run again and sold it.  When I bought it it would pulse and smoke black at idle and die with throttle.

New tps installed and it won’t run period.  I went to celebrate it and I’m getting 5 volts on 2 of the 3 wires running to the tps.  Is this normal and if so how should I celebrate it?

[JacobSlabach]

TPS wires come straight from the ecu so would that be shot or is there something else that would be effecting it?

[JacobSlabach]

Found out the ecu is off of a sportsman lol would that affect it at all?  As far as I know it’s the same motor the only differences that I can think of would be this model doesn’t have EPS and scramblers are tuned more aggressive then sportsmans

[MarkinAR]

They are different part numbers so there's a good chance they are different.  I think a lot of motor and trans stuff is the same but I'd bet electronics are different.

[JacobSlabach]

now heres an idea:  i still have my other 2013 scrambler 850 LE (with EPS).  could i swap computers and see how my busted scrambler runs or not?  i believe the models are the same except one has EPS

[JacobSlabach]

I’m going to see how much a new Scrambler 850 computer is for it from Polaris cause I really don’t want to take the computer off my other bike it’s a pain to do and the wiring job on the base model from the former owner is shady I’d rather not screw my good ecu😂

[MarkinAR]

I wouldn't try it either, i'd hate for 2 wires to be crossed in the plug and burn your good one.  Check ebay, I bet there's a good used one out there.

[JacobSlabach]

agreed.  cheapest i can find it about 150 tho..  i guess if it dont work i can return it..

and thats another thing.. yall think two wires could be crossed on it?  the whole bike has been rebuilt... wiring harness has been chopped up some here and there and its got a new crank case on it

[JacobSlabach]

hows the best way to check to make sure the wires are not crossed?

[MarkinAR]

Your guess is as good as mine on wiring.  I usually scour the interwebs and look for a wiring diagram then get to color mapping everything.  I have no experience on Polaris machines.

[JacobSlabach]

ok thanks.  i did download the manual from here and am going through it.  i assume there would be a wiring diagram in there?

[JacobSlabach]

i dont see the wiring diagram in the manual which surprises me.  it even has a electrical section where i thought it would be but ive searched through the whole manual to no avail.  guess ill have to look on good ol' images and try and find one lol

[JacobSlabach]

update on this bike, found a wiring diagram, checked wiring, and its all good.  swapped ECUs with my other scrambler and the ECU is good.  took the bike to my local polaris dealer to dial in the tps and they charged me $100 to say the diagnostic tool said the new tps was toast.  so back to the drawing board.  ive heard of the timing gear on the cam jumping time on these machines so that may be an issue.. will check that also.

[JacobSlabach]

Got two codes I’m tryna figure out both have to do with the injectors.  See attached pic.  Any ideas as to what would cause this?

[MarkinAR]

Odd both injectors would have the same code. Each has a separate hot wire but I bet there's a common ground. Id look for a broken ground wire or dirty ground to frame. For that matter, check the negative battery terminal contact. 

[JacobSlabach]

alright will do, also found that theres no spark either.  so no spark and no fuel.  it has compression and the timing is good.  could the TPS being out of adjustment make it not get spark or fuel?  it was pulse-running when i bought it (pulsed at idle and i couldnt give it more then 1/4 throttle without it dying)

[JacobSlabach]

another thing i just realized while looking through the service manual is i dont hear the fuel pump coming on when i turn on the ignition.  the plug is hooked up to the pump and i do have the airbox installed (it has the idle air control valve on the side so it has to be installed and hooked up for the pump to come on)

[JacobSlabach]

update: i found that the 20a efi fuse was blown so i replaced it and now the fuel pump comes on with the key but still has the same engine lights and wont fire.

[MarkinAR]

It won't fire if it doesn't detect fuel. My guess is a bare spot on the harness rubbing against the frame. It takes a direct short to pop a 20A fuse. 

[JacobSlabach]

8 minutes ago, MarkinAR said:

It won't fire if it doesn't detect fuel. My guess is a bare spot on the harness rubbing against the frame. It takes a direct short to pop a 20A fuse. 

alright makes sense.  ive been through the whole wiring harness and nothing seems worn or bare.  traced all the wires and the ground wires from the injectors run directly to the ecu.  positives run to the efi relay which i switched with another relay to make sure its good and no change there.  theres a black box in the wiring harness that has wires chopped and reconnected to it im curious what that is.

...or if it has anything to do with my issue.. and i swapped the ecu to my other scrambler LE and it ran just fine, used and tried averything i could think of and it checked out

Edited April 20, 2021 by JacobSlabach

[MarkinAR]

I hate chasing electrical gremlins.  Still leaning towards it being a direct short to ground. Could it be the reg/rect pumping out too much voltage and causing a problem?  Without it running that's probably difficult to troubleshoot.

I'd really dig into that area where wires were chopped and reconnected and then go from there.  You might loosen the harness from the frame and pull it away the best you can to put space between the harness and the frame and then see if that helps.  May not, but worth a shot maybe.

[JacobSlabach]

19 hours ago, MarkinAR said:

I hate chasing electrical gremlins.  Still leaning towards it being a direct short to ground. Could it be the reg/rect pumping out too much voltage and causing a problem?  Without it running that's probably difficult to troubleshoot.

I'd really dig into that area where wires were chopped and reconnected and then go from there.  You might loosen the harness from the frame and pull it away the best you can to put space between the harness and the frame and then see if that helps.  May not, but worth a shot maybe.

alright theres also one more thing ive seen on all the polaris bikes but not sure what it is ill take a picture of it and post it.  i traced the wires from the little black box (pretty sure its a relay) and wires run out of it to the left handlebar and the the other wires run to the headlights so i thin its just the headlight low beam/high beam relay and the headlights work as they should.  im with you on the wiring if id have known it wasnt just a faulty TPS on this bike i wouldnt have bought it lol

[JacobSlabach]

update:  went to show a buddy what the scramblers issue was and it fired up.  it idles rough still and only runs on one cylinder but at least its running.  i guess the ecu just had to have a while to reset itself?  i also think i blew the fuse when i installed the last TPS incorrectly (reversed two of the wires).  also the code 520 194-7 (manual says stuck throttle) is the only code on the bike now, the two for the injectors are cleared