Polaris Code 31 - Your Complete Guide To Diagnosing And Fixing It

You’re geared up for a day on the trails, you turn the key, and there it is—the dreaded check engine light. Your Polaris dash flashes a fault code, and you see the numbers: 31. Your heart sinks a little, and your mind starts racing. What does it mean? Is this a simple fix or a trip-ending disaster?

That flashing light and error message are your machine’s way of telling you something is off with the Air Temperature Sensor circuit. This small but vital sensor affects your engine’s performance, fuel efficiency, and starting reliability. Ignoring it can lead to a rough ride and bigger headaches down the road.

Imagine confidently diagnosing the problem yourself, grabbing a few simple tools, and fixing the issue right in your own garage. You can save a costly trip to the dealer and get your machine back on the dirt where it belongs, running stronger than ever.

In this complete polaris code 31 guide, we’ll walk you through everything you need to know—from what the code means to a step-by-step process for finding and fixing the root cause. Let’s get that light turned off and get you back to riding.

What Exactly is Polaris Code 31? Breaking Down the Fault

First things first, let’s demystify the code. When your Polaris displays Code 31, it’s officially flagging an issue: Air Temperature Sensor Circuit High / Open. In plain English, your machine’s brain, the Engine Control Unit (ECU), isn’t getting a proper signal from the sensor that measures the temperature of the air going into your engine.

This sensor is often part of a combined unit called a T-MAP sensor, which measures both Temperature and Manifold Absolute Pressure. The ECU uses this temperature data to calculate the perfect air-to-fuel ratio for combustion.

Think of it like a chef adjusting a recipe. Cold, dense air needs more fuel, while hot, thinner air needs less. When the ECU can’t read the air temperature, it has to guess. This guess is usually a “fail-safe” setting that runs the engine rich (too much fuel) to prevent damage, which leads to a host of other problems.

Symptoms to Watch For: How Code 31 Affects Your Ride

Your machine will usually give you more clues than just a number on the dash. Because the air/fuel mixture is off, you’ll likely notice some performance issues. Keep an eye out for these common symptoms that often accompany a polaris code 31.

Poor or Rough Idle: The engine might sputter or idle erratically because it can’t find a stable fuel mixture.
Difficulty Starting: Cold starts can be especially tough when the ECU doesn’t know how cold the air is.
Reduced Engine Performance: You might feel a noticeable loss of power, hesitation during acceleration, or find the machine has gone into a “limp mode.”
Increased Fuel Consumption: The engine’s default fail-safe mode is to run rich, which means you’ll be burning through fuel much faster than usual.
Black Smoke from Exhaust: This is a classic sign of an engine running rich, as unburnt fuel exits through the exhaust.

Common Problems with Polaris Code 31: The Usual Suspects

Now that you know what the code means and what it does, let’s hunt down the cause. Fortunately, the list of potential culprits is short, and you can check most of them with basic tools. These are the most common problems that trigger the code.

1. Damaged Wiring or a Loose Connection

This is the number one cause on off-road vehicles. Your Polaris endures constant vibration, mud, water, and impacts from trail debris. All that abuse can easily damage a wire or jostle a connector loose.

The connection at the sensor itself can get packed with mud or corrode from moisture, leading to a bad signal. Always check the simple, physical stuff first!

2. A Failed Air Temperature Sensor

Like any electronic component, sensors can simply fail over time. The internal electronics can burn out or degrade, causing them to send an incorrect or no signal at all to the ECU. This is a very common point of failure.

3. A Dirty or Contaminated Sensor

The tip of the air temperature sensor sits directly in the path of incoming air. If your air filter is dirty or if there’s any oil blow-by from the crankcase, the sensor can get coated in a layer of grime. This film insulates the sensor, preventing it from accurately reading the air temperature.

4. A Problem with the ECU

This is extremely rare, so always treat it as the absolute last resort. Before you even consider a faulty ECU, you must exhaustively rule out the sensor and the entire wiring harness. An ECU failure is possible, but it’s not the place to start your diagnosis.

How to Fix Polaris Code 31: Your Step-by-Step Guide

Alright, it’s time to get your hands dirty. This section provides the how to polaris code 31 roadmap. Grab your basic hand tools, a multimeter, and some contact cleaner. Remember to work in a well-lit area.

Safety First: Before you begin, make sure the engine is completely cool and disconnect the negative terminal of your battery to prevent any accidental shorts.

Step 1: Locate the Air Temperature Sensor

The sensor is typically located in one of two places: either on the airbox itself or, more commonly, on the intake boot or throttle body between the airbox and the engine. It will have a wire connector plugged into it. On many modern Polaris models (like RZRs, Rangers, and Sportsmans), it’s integrated into the T-MAP sensor.

Step 2: Inspect the Wiring and Connector

This is your most likely fix. Follow the wiring harness from the sensor back as far as you can. Look for any signs of damage:

Chafing or cuts in the insulation.
Pinched wires from zip ties or frame contact.
Melted sections from being too close to the exhaust.

Next, carefully unplug the connector from the sensor. Inspect the pins on both the sensor and in the connector. Are they clean and shiny? Or are they green with corrosion or packed with dirt? Spray both ends with electrical contact cleaner and let them dry fully before reconnecting firmly.

Step 3: Clean the Sensor (If Possible)

If the wiring looks good, the next step is to clean the sensor. Carefully unbolt it from the intake. You’ll see a small bulb or element at the tip—this is the part that reads the temperature.

Grab a can of Mass Airflow (MAF) Sensor Cleaner. Do not use brake cleaner or carburetor cleaner, as they are too harsh and can damage the delicate sensor. Spray the sensor element generously and let it air dry completely. Never touch or scrub the element.

Step 4: Test the Sensor with a Multimeter

If a visual inspection and cleaning don’t solve the problem, it’s time to test the sensor itself. Set your multimeter to measure resistance (Ohms Ω). Place the probes on the two pins of the sensor that correspond to the temperature circuit (you may need a service manual wiring diagram for this).

You should get a resistance reading. The exact value will change with temperature, but you’re looking for a plausible number (e.g., 2000-3000 ohms at room temp). If you get an open circuit (“OL”) or zero resistance, the sensor is bad. This is one of the best polaris code 31 tips for confirming a failed part before you buy a new one.

Step 5: Replace the Sensor

If your sensor is confirmed bad, replacement is the only option. We recommend using a genuine OEM Polaris part for the best fit and reliability, but high-quality aftermarket sensors are also available. Installation is simple—just bolt the new one in place and plug it in.

Step 6: Clear the Code and Test Ride

After your repair, reconnect the battery. Start the machine and let it run for a few minutes. On most models, the code will clear itself after a few successful run cycles. If it doesn’t, you can fully clear it by leaving the battery disconnected for about 15 minutes. Take it for a short test ride to ensure the code doesn’t return.

The Benefits of Fixing Polaris Code 31 Promptly

You might be tempted to ignore that light, but fixing the issue offers significant benefits. Properly addressing this fault code isn’t just about making a light go away; it’s about restoring the health and performance of your machine.

Restored Engine Performance: Get your machine’s power and throttle response back to where it should be.
Improved Fuel Economy: A correct air/fuel mixture means you’ll stop wasting fuel and can ride longer on a tank.
Easier Starting and Smoother Idle: Your machine will start more reliably and idle smoothly, just like it did from the factory.
Preventing Further Damage: Running rich for too long can foul spark plugs and contaminate your engine oil, leading to more expensive repairs.
Peace of Mind on the Trail: Nothing beats the confidence of knowing your machine is running in top condition when you’re far from the trailhead.

Best Practices for Prevention: A Sustainable Polaris Code 31 Care Guide

The best repair is the one you never have to make. Following a few polaris code 31 best practices during your regular maintenance can prevent this code from ever appearing. This approach is also a more sustainable and eco-friendly way to own your machine.

A well-maintained engine runs efficiently, using less fuel and producing fewer emissions. Your preventative care is good for your wallet and the environment.

Start by regularly cleaning or replacing your air filter. A clogged filter can let fine dust through that contaminates the sensor. During washes, take an extra minute to inspect the wiring harnesses you can see. Finally, consider applying a small amount of dielectric grease to the sensor connector to seal out moisture and prevent corrosion—a must for riders who love mud and water crossings.

Frequently Asked Questions About Polaris Code 31

Can I still ride my Polaris with Code 31?

You can, but it’s not recommended for long distances. The machine will likely run poorly, use excessive fuel, and could potentially foul spark plugs. It’s best to diagnose and fix the issue as soon as possible to avoid causing other problems.

How much does it cost to fix Polaris Code 31?

The cost can vary widely. If it’s a dirty connector or a loose wire, the fix is free! If you need to replace the sensor yourself, the part typically costs between $50 and $150. If you take it to a dealer, you can expect to pay for the part plus 1-2 hours of labor, potentially totaling $200-$400 or more.

Where is the air temp sensor on my RZR/Sportsman?

On most modern Polaris models, it is part of the T-MAP sensor located on the plastic intake tube or aluminum throttle body, just after the air filter box. However, locations can vary slightly by model and year. Your best bet is to consult your specific service manual for the exact location.

I replaced the sensor, but the code came back. Now what?

If a new sensor doesn’t fix the problem, the issue is almost certainly in the wiring harness between the sensor and the ECU. You’ll need to carefully re-inspect every inch of the wires for a hidden break or short. If the wiring is confirmed to be perfect, only then should you consider having a dealer test the ECU.

Tackling a polaris code 31 might seem daunting at first, but with the right steps, you can be your own hero. You now have the knowledge to inspect, diagnose, and fix one of the most common issues Polaris owners face. Wrench smart, stay safe, and we’ll see you back on the trail!

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Thomas Corle

Founder & Automobile expert at FatBoysOffroad

Automobile expert and off-road enthusiast, sharing in-depth knowledge of vehicles, gear, and adventures. Helping readers make smart decisions and enjoy the thrill of off-roading safely and confidently.