There’s nothing worse than being deep in the backcountry on your Polaris RMK 800 when that dreaded check engine light flashes on, displaying a cryptic code. Seeing the polaris rmk 800 520335 codes can sink your heart, leaving you worried about a long, slow ride home in limp mode.
But don’t panic. This code is often a straightforward fix you can handle yourself with a few basic tools and a bit of know-how. We promise this guide will walk you through exactly what that code means, how to diagnose it like a pro, and how to get your sled back to peak performance.
We’ll break down the common causes, give you a step-by-step troubleshooting plan, show you the tools you’ll need, and share some pro tips to prevent it from happening again. Let’s get that sled fixed and get you back on the snow.
What Exactly Are Polaris RMK 800 520335 Codes?
First things first, let’s decode the message your sled is sending you. A “520335” is a specific Diagnostic Trouble Code (DTC) stored in your sled’s Engine Control Unit (ECU). It points directly to a problem within the Exhaust Gas Temperature (EGT) sensor circuit.
On a high-performance 2-stroke engine like the one in your RMK 800, the EGT sensor is a critical safety component. It constantly measures the temperature of the exhaust gases leaving the cylinder.
This information tells the ECU how the engine is running. If temperatures get too high (a “lean” condition), the ECU can add more fuel to cool things down and prevent catastrophic engine damage like a piston meltdown. When the ECU can’t get a reliable signal from this sensor, it throws the 520335 code and puts the sled into a protective “limp mode” to be safe.
Understanding the FMI Number
Often, the main code will be paired with a secondary number called a Failure Mode Identifier (FMI). This gives you a massive clue about the type of problem. Here are the most common ones you’ll see with 520335:
- FMI 3 or 4: These usually mean “Voltage Above/Below Normal.” This strongly suggests a wiring issue, like a wire that’s shorted to ground or another wire.
- FMI 5: This means “Current Below Normal / Open Circuit.” This is the most common and almost always points to a broken wire, an unplugged connector, or a completely failed EGT sensor.
Common Problems and Symptoms Triggering Code 520335
Before you even grab a wrench, you need to recognize the symptoms and understand the likely culprits. This part of our polaris rmk 800 520335 codes guide will help you narrow down the possibilities.
Telltale Signs Your Sled is in Distress
When the EGT circuit fails, your RMK will let you know. The signs are usually impossible to ignore:
- Check Engine Light (CEL): This is your first and most obvious warning. The light will illuminate on your gauge cluster.
- Limp Mode: The sled will feel sluggish and won’t rev out properly. This is the ECU intentionally limiting power to protect the engine.
- Poor Performance: Even if not in full limp mode, you may notice hesitation, bogging, or generally poor throttle response as the ECU defaults to a rich, safe fuel map.
The Usual Suspects: What Causes the Fault?
While it seems complex, over 95% of 520335 codes are caused by one of three things. The most common problems with polaris rmk 800 520335 codes are almost always physical, not electronic.
- A Failed EGT Sensor: This is the number one cause. The sensor lives in the harsh environment of the exhaust pipe, and the constant heat cycles and vibration eventually cause it to fail internally.
- Damaged Wiring: The sensor’s wire is routed near hot exhaust components and a vibrating engine. It’s common for the wire to melt, get chafed through on the chassis, or break from vibration.
- A Bad Connection: The electrical connector for the sensor can become corroded from moisture or simply vibrate loose over time, causing an open circuit.
How to Diagnose Polaris RMK 800 520335 Codes: A Step-by-Step Guide
Alright, let’s get our hands dirty. This is the “how to” section you’ve been waiting for. Follow these steps methodically, and you’ll pinpoint the problem in no time.
Safety First: Pre-Check Essentials
Before you start, make sure the sled is safe to work on. Park it on a level surface, turn the engine off, and remove the key.
Most importantly, let the exhaust cool down completely. The EGT sensor and exhaust pipe can cause severe burns.
Essential Tools for the Job
You don’t need a full shop, just a few key items:
- A good quality Digital Multimeter (this is non-negotiable)
- Basic wrench or socket set (a 13mm or 1/2″ is often needed for the sensor)
- Flashlight or headlamp
- Zip ties and wire cutters
- Dielectric grease
- Penetrating oil (like PB Blaster or Kroil) if the sensor is rusty
Step 1: The Visual Inspection
Start with the easiest check. Find the EGT sensor—it’s the small probe screwed into the side of the exhaust pipe (the “Y-pipe”) with a single wire coming out of it.
Carefully trace that wire from the sensor all the way back to where it plugs into the main wiring harness. Look for any signs of damage: melted insulation, shiny copper showing through, sharp kinks, or areas where it’s been rubbing against the frame or engine.
Step 2: Check the Connector
Follow the wire to its connector. It’s usually a small, single-pin weatherproof plug. Disconnect it by pressing the locking tab and pulling the two halves apart.
Shine your light inside both ends of the connector. Are the metal pins clean and shiny? Or do you see green or white crusty corrosion? A corroded connection can easily cause this fault code.
Step 3: Testing the EGT Sensor with a Multimeter
This is the definitive test that separates a wiring problem from a sensor problem. Grab your multimeter and set it to the Ohms (Ω) setting, usually in the 2k range.
- Take the probe from the sensor side of the connector you just unplugged.
- Touch one lead of your multimeter to the metal pin inside the sensor’s connector.
- Touch the other lead to the metal body of the sensor itself (the part that screws into the pipe).
A healthy, functioning EGT sensor at room temperature should read somewhere between 200 and 240 Ohms. If you see a reading in this range, your sensor is likely good, and your problem is in the wiring harness.
If your multimeter reads “OL” (Over Limit or Open Loop) or “0.0”, your sensor has failed. “OL” indicates a broken circuit inside the sensor, and “0.0” indicates an internal short. In either case, the sensor needs to be replaced.
The Fix: Replacing Your RMK 800 EGT Sensor
If your multimeter test condemned the sensor, replacement is your only option. The benefits of replacing a faulty sensor are huge: you’ll restore full power, protect your engine, and gain peace of mind on the trail.
First, if the sensor looks rusty, give it a good spray with penetrating oil and let it soak for 15-20 minutes. This will make removal much easier and prevent you from stripping the threads in the pipe.
Using the correct size wrench, carefully unscrew the old sensor from the exhaust pipe. Sometimes they can be tight, so use steady pressure.
Before installing the new sensor, apply a small amount of high-temp anti-seize compound to the threads. This will make it much easier to remove in the future. Thread the new sensor in by hand to avoid cross-threading, then tighten it snugly with your wrench. Do not over-tighten it.
Finally, route the new wire carefully. Use zip ties to secure it away from the hot pipe and any sharp edges on the chassis. Plug it into the harness connector, and consider adding a small dab of dielectric grease to keep moisture out.
Preventative Maintenance: Your EGT Sensor Care Guide
Want to avoid seeing this code again? Following a few polaris rmk 800 520335 codes best practices can make a huge difference. This is your long-term care guide for a reliable sled.
Proactive Wiring Checks
Make inspecting the EGT sensor wire a part of your regular pre-ride check. Just a quick glance to ensure it’s secure and not rubbing on anything can save you a headache on the snow.
If the factory routing looks vulnerable, don’t be afraid to add a piece of protective wire loom or an extra zip tie to keep it safe.
Eco-Friendly and Sustainable Riding
Thinking about sustainable off-roading might seem odd, but proper maintenance is key. A sled with a faulty EGT sensor runs in a rich, inefficient limp mode, burning more fuel and creating more emissions than necessary.
By ensuring your sensors are working correctly, you’re not just protecting your engine—you’re making sure it runs as cleanly and efficiently as designed. This is a core part of being a responsible and eco-friendly rider.
Frequently Asked Questions About Polaris RMK 800 520335 Codes
Can I still ride my RMK with code 520335 active?
You can, but you shouldn’t. The sled will be in a power-reduced limp mode designed to get you back to the truck, not to continue your ride. Riding for an extended period without a functioning EGT sensor puts your engine at unnecessary risk.
How do I clear the code after I’ve fixed the problem?
In most cases, the code will clear itself after you’ve ridden the sled through a few heat cycles (starting it, letting it warm up, riding, and letting it cool down). If the ECU no longer detects the fault, it will turn off the check engine light automatically.
Is an aftermarket EGT sensor as good as the OEM Polaris part?
Quality can vary. While some aftermarket sensors work well, we at FatBoysOffroad generally recommend sticking with the OEM Polaris sensor. The price difference is often minimal, and you’re guaranteed the correct resistance values and durability for your specific sled.
What if I replace the sensor and the code comes back?
If a new sensor doesn’t fix the issue, your problem lies in the wiring harness between the sensor connector and the ECU. You’ll need to use your multimeter to perform a continuity test on that wire to find the break or short. This is more advanced, and if you’re not comfortable with wiring diagrams, it might be time to visit a trusted mechanic.
Tackling diagnostic codes can feel intimidating, but the polaris rmk 800 520335 codes are a perfect entry into DIY diagnostics. By following these steps, you’ve learned how to inspect, test, and replace one of your sled’s most important sensors.
You’ve not only saved yourself a trip to the dealer but also gained a deeper understanding of how your machine works. Now you have the knowledge and confidence to solve this common problem. Get back out there, ride hard, and ride safe!
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