It went away, I think I started it in high and reverse too many time. Yes, I am an over stressed idiot!

 

If this comes back try reseating the crank position sensor connector. Its located just below and behind the transmission shifter.

 

How do you reset it

 

Thanks

 

Code 21; SYNCHRONIZATION ERROR. You get this when you have a misfire. Most likely electrical, but also can be fuel related. It is not a very specific code.

 

Trust me it's the Crank sensor. It sets the point to tells the ECM when to fire spark, fuel injectors, etc. The Synchronization of the the CPS and crankshaft position takes place during the first two revolutions each time the engine is started. If the sensor fails or becomes disconnected for any reason the engine will quit running. It only has to fail momentarly to throw a code. For whatever its worth. If it happens again, clean and reseat the connector.

 

Has not come back. But I am overly watching this thing now.

 

And it may not come back, but at least you now have an idea where to look. The biggest percent of problems are bad connections. That is always the first place to start. Between the vibration, dirt, water etc, something is bound to go wrong.

 

Thanks N0OSV..........is always good to know!

 

I have a similar problem.
I run into water and mud, after 30 minutes when I speed up the engine sounds like misfiring.
I was at the beach, then I wide open the throttle and speed up with no problem.
When I slow down start doing the same thing loosing rpm and sounds like misfiring.
Check display and shows engine check. The code is 21. I disconnected some sensors and connect them back.

Then run for a while and start doing the same thing.
Any Idea?

 

A really good idea also, if you unplug anything , before you plug it back in dielectric grease the hell out of it.

 

I've had a bad injector cause this code

 

Have you checked to make sure the plug boots are seated. I know it sounds stupid but I've seen them come loose while riding and dirt gets under then and they feel like they are seated but actually aren't.

 

I have a 2010 rzr4 800 Polaris efi. Was driving around for like 5 minutes and she shut off. Pulled the codes up and it’s showing code 21 any suggestions.