I was driving around and the vehicle lost power suddenly. The EFI light came on solid beside the Park light.

I waited a second and the light went off. I had full power and no problems since.

How would I go about finding what the fault was.

[2015 Z Force 800 53/Trail EPS]

As I recall they don't retain fault codes so even if you had one of their readers you couldn't see a stored code. If it had continued to stay on the manual shows how to read the codes as well as has a list. Not too many things that generate a fault code causes the engine to die of loose power but a couple are: Low fuel pressure or Low battery or system voltage. 

Sadly it bogged down to idle with no power and the EFI light was solid for 10 secs again. It looks like something might be wrong. I read the manual but don't have time in the 10 seconds its happening to check the EFI code. I happens without warning once every 2hrsish of driving hard.

[2015 Z Force 800 53/Trail EPS]

Sadly it bogged down to idle with no power and the EFI light was solid for 10 secs again. It looks like something might be wrong. I read the manual but don't have time in the 10 seconds its happening to check the EFI code. I happens without warning once every 2hrsish of driving hard.

Every 2 hours...ish... just about the time it takes to make a lot of vacuum on a fuel tank when the check valve is stuck shut. Next time it happens jump out and loosen the gas cap and listen close for the sound of air being sucked back in...not out, out would be normal pressure.

Good catch NMK. hopefully the OP will post he's findings.

[2015 Z Force 800 53/Trail EPS]

Good catch NMK. hopefully the OP will post he's findings.

Probably isn't..if it was it should come on slowly...but it's something to check..along with the pump's connections.

It wasn't the fuel tank. No pressure either way after the fault occurred. I went out for a couple of hours today and it only did it once. This time the fault only flashed the light on the cluster panel. Its very annoying losing all power instantly then recovering on its own. Prob never get fixed. Dealer wont be able to reproduce. That means it will never be addressed. Its not like they are guna ride it hard for 1-3 hrs to watch it blip in power and toss a 1to5 sec efi light.

I guess my only hope is to wear a go pro. Then at least they wont think I am crazy.

[2015 Z Force 800 53/Trail EPS]

May be low power so the first place to check is that accursed main fuse holder. The fuse will be fine but the crimps inside the holder were made loose on hundreds of harnesses. Hard to check but look for any resistance through the holder and/or any sign it been hot. It's in the back compartment under the driver's seat. There might be two there-one is for the PS and the other is your systems supply.

If it were my machine, I would check every connection in the engine management loom.

It only takes one intermittent sensor or weak contact connection to give the kind of behavior you are seeing.

The MIL lamp and engine dropping to idle but not stalling is a clue. I would run that by the dealer's mechanic.

Myself I'm done with this product, not so much as the unit itself more the terrible lack of support from the manufacturer & the distributor........there I've said it

I see tracks in the OP's photo, one of my last bad experiences was finding an electrical issue with a ZF800 Trail. Took several months to nail it down as it would come & go....heat related as this one sounds. The tracks are going to aggravate the problem if it is the same issue I had.

Won't bore you with the diagnostics process to find the issue, I will suggest where the problem might be. The EFI harness the one from the engine to the ECU in the front compartment.....is poorly routed over the exhaust leaving the engine. Incredible heat is obviously built up there & would be aggravated with the tracks. There are splices inside that harness that you cannot see, I was not allowed to cut the harness open....I wanted to so badly  as I had identified & proven it was an intermittent heat related 5vdc low problem.

If the basics covered that have been suggested, that is very important first & foremost. Then I would look toward this harness 

Funny that it has only happened after some running time and when the machine is pushed very hard. With tracks and a top speed of 70klm my machine runs a lot at pedal to the metal. The cabin really heats up. Even at <0 degrees Celsius <32 degrees Fahrenheit. I drive it in the cold on snow since I got it. I have never seen more than 3 bars on the temp gauge but there is a intense heat radiating from that engine. I will try my best to figure out what the running temperature of that wiring harness.

Any ideas on how to fix it if heat on that wire is a issue?

So, if the problem is due to heat on the EFI wiring harness and the machine slows down is it because of voltage drop and a sensor picks that up or is it because there is a problem within the harness itself?   Does anyone know if this is a safety feature built into the computer?  If it is because of voltage drop could a person just turn off the lights to stop this from happening?  The reason I ask is because this has happened to me and I always run with lights on.

[2015 Z Force 800 53/Trail EPS]

So, if the problem is due to heat on the EFI wiring harness and the machine slows down is it because of voltage drop and a sensor picks that up or is it because there is a problem within the harness itself?   Does anyone know if this is a safety feature built into the computer?  If it is because of voltage drop could a person just turn off the lights to stop this from happening?  The reason I ask is because this has happened to me and I always run with lights on.

There is no safety like that built-in. If it slows down its because something is effecting the system..most likely fuel pressure...and that also will turn the MIL light on. There have been a few reports of the tank vent check valve getting stuck either open of shut...and shut it will not allow the air in to replace the fuel being taken out...which creates a vacuum...which the fuel pump can only fight so much before pressure and volume is reduced. Next time this happens stop, shut it off so you can hear, then crack the gas cap. If it sucks air in..that's what it is and I will tell you how to fix it.

NMK - All three times this has happened I took the gas cap off, kept it off for a short while and put it back on.  Doing that had no effect on how how it ran.  As I think back what made it run better was turning the engine off, let it sit a while, then turn it on and listen that the electric fuel pump came on.  This worked and supplied enough gas to make it run good for a while.  Then after a few miles it lost power again, so I shut it down and cycled the fuel pump again and it ran again.  I believe you may be correct about the fuel pressure not where it needs to be consistently.  I'm going to take it in, but I thought I'd ask about the voltage drop first.  Thanks for all of your input and I'll post back if/when they do anything about the problem.  Hopefully in a few weeks I can take it to them, but right now none essential travel isn't permitted over 50 miles and the dealer is farther than that.