There’s nothing that kills the thrill of a pre-ride check faster than turning the key and seeing that dreaded check engine light glaring back at you. You pull out your code reader, and it flashes a code that seems cryptic: polaris engine code p0118. Your mind starts racing—is this serious? Is my weekend ride ruined? Is this going to be an expensive trip to the dealer?
Take a deep breath. While that light is annoying, P0118 is one of the most common and manageable codes you can encounter on your Polaris. We promise that you, the capable home mechanic, can absolutely tackle this problem with the right guidance.
This complete guide will walk you through everything. We’ll break down what the code means in plain English, show you the exact symptoms to look for, and give you a step-by-step plan to diagnose and fix the issue yourself. Let’s get that light off and get you back on the trail.
What Exactly is Polaris Engine Code P0118?
At its core, the diagnostic trouble code (DTC) P0118 stands for “Engine Coolant Temperature (ECT) Sensor Circuit High Input.” That sounds complicated, but let’s simplify it.
Your Polaris has a small but vital sensor called the Engine Coolant Temperature (ECT) sensor. Its only job is to measure the temperature of your engine’s coolant and report that information to the main computer, the Engine Control Unit (ECU).
The ECU uses this data to make critical decisions about how the engine runs—things like adjusting the fuel-to-air mixture, controlling ignition timing, and deciding when to kick the radiator fan on. A “high input” fault means the ECU is receiving a voltage signal from the sensor that is higher than the normal operating range. Paradoxically, the ECU often interprets this high voltage (caused by high resistance) as an impossibly cold temperature, like -40°F.
So, even if your engine is fully warmed up, the P0118 code means your ECU is convinced it’s operating in arctic conditions, leading to all sorts of performance problems.
Telltale Symptoms: How Your Polaris Acts with a P0118 Code
When your machine’s brain thinks it’s freezing cold, it will act accordingly. You’ll likely notice one or more of these common problems with polaris engine code p0118 before you even plug in a scanner.
- The Obvious Check Engine Light: This is your first and most direct clue that something is wrong.
- Hard Starting, Especially When Warm: The ECU is dumping extra fuel for a “cold start” into an already warm engine, making it difficult to fire up.
- Poor or Rough Idle: The incorrect fuel mixture can cause the engine to stumble, surge, or idle erratically.
- Black Smoke from the Exhaust: This is a classic sign of a rich fuel condition (too much gas, not enough air), which happens when the ECU is over-fueling for cold weather.
- Terrible Fuel Economy: Burning all that extra fuel will drain your tank much faster than usual.
- Radiator Fan Running Constantly (or Not at All): The ECU uses ECT data to control the fan. With a bad signal, it may run the fan nonstop or fail to turn it on when the engine is actually hot, creating a real overheating risk.
The Usual Suspects: Common Causes of P0118
Fortunately, the list of potential culprits for this code is short. In our experience, it almost always comes down to one of three things, ranging from most to least likely.
The ECT Sensor Itself Has Failed
This is the most common cause. The ECT sensor lives in a harsh environment of heat cycles and vibration. Over time, its internal components can simply wear out and fail, sending an incorrect signal back to the ECU.
Damaged Wiring or a Loose Connection
This is a close second, especially for off-road machines. Mud, water, high-pressure washing, and trail debris can all wreak havoc on your wiring harness. A wire could be frayed, a pin inside the connector could be corroded, or the connector itself might just be loose or filled with grime.
A Faulty Engine Control Unit (ECU)
Let’s be clear: this is extremely rare. Before you even consider the ECU, you must exhaustively rule out the sensor and the wiring. An ECU failure is the absolute last resort in your diagnosis.
Your Step-by-Step Polaris Engine Code P0118 Guide to Diagnosis
Alright, let’s get our hands dirty. Grab your basic tools and follow this logical process. This is the exact how to polaris engine code p0118 diagnostic procedure we use in the shop.
Safety First: Always work on a cool engine to avoid burns. It’s also a good practice to disconnect the negative battery terminal before working on electrical components.
Step 1: The Visual Inspection (The 5-Minute Check)
Start with the easiest stuff. First, locate the ECT sensor. On most Polaris models (like RZRs and Rangers), it’s a small, two-wire sensor, typically brass, threaded into the engine head or thermostat housing. Follow the upper radiator hose to the engine, and you’ll likely find it nearby.
Once you find it, look closely at the wiring harness leading to it. Are there any obvious signs of damage—cuts, chafing against the frame, or melted spots from touching the exhaust? Check that the connector is plugged in securely and clicks into place.
Step 2: Inspect the Connector
Carefully unplug the electrical connector from the sensor. You might need a small flathead screwdriver to gently release the locking tab. Now, inspect the metal pins on both the sensor side and the harness side. Look for any green or white crusty buildup—that’s corrosion. Also, check for pins that are bent, broken, or pushed back into the plastic housing.
If you see dirt or mild corrosion, spray both sides with a quality electrical contact cleaner and use a small brush to gently clean the terminals. Let it dry completely before reconnecting.
Step 3: Test the ECT Sensor
This is the definitive test to see if the sensor is bad. You’ll need a simple digital multimeter set to measure resistance (Ohms, Ω). With the sensor still unplugged, place one multimeter probe on each of the two pins on the sensor itself.
The resistance reading will change with temperature. A service manual will give you exact specs, but a good rule of thumb is: on a cold engine (e.g., 70°F), you should see a reading of around 2,000-3,000 Ohms. On a fully warmed-up engine, the resistance should drop significantly, often below 300 Ohms. If you get an “OL” (Open Loop/infinite resistance) reading or a reading of zero, the sensor is bad.
Step 4: Test the Wiring (If the Sensor is Good)
If your sensor tested fine, the problem is likely in the wiring between the sensor and the ECU. This is a bit more advanced but doable. Set your multimeter to the continuity setting (it usually has a sound icon that beeps). You’ll need to know which pins on the main ECU connector correspond to the ECT sensor (a service manual is your best friend here).
Test each of the two wires individually by placing one probe on the pin at the sensor connector and the other on the corresponding pin at the ECU connector. You should hear a beep, indicating a solid connection. If there’s no beep, you have a break in that wire somewhere in the harness.
The Fix: How to Replace Your Polaris ECT Sensor
If your diagnosis pointed to a bad sensor, you’re in luck. This is a fast, cheap, and easy repair. Following this polaris engine code p0118 care guide will get it done right.
Tools and Parts Needed:
- New OEM or quality aftermarket ECT Sensor
- Deep socket and ratchet (size varies by model)
- Fresh, correct-type Polaris-approved coolant
- Shop rags
- Funnel
-Clean coolant drain pan
- Step 1: Drain a Little Coolant. Place your drain pan under the machine. You don’t need to drain the whole system. Just loosen the radiator cap to release pressure, then open the drain plug or remove the lower radiator hose just long enough to drain the coolant level below the sensor’s location.
- Step 2: Remove the Old Sensor. With the connector unplugged, use your deep socket to unscrew the old sensor. Have a rag ready to catch any minor drips.
- Step 3: Install the New Sensor. Check if your new sensor came with a sealing washer or has thread sealant pre-applied. If not, apply a small amount of thread sealant. Thread the new sensor in by hand to prevent cross-threading. Then, use your socket to snug it down. Don’t overtighten it—snug is good.
- Step 4: Reconnect and Refill. Plug the electrical connector back in firmly until it clicks. Using your funnel, slowly refill the cooling system with fresh coolant until it reaches the proper level.
- Step 5: Burp the System. This is a crucial pro tip! Leave the radiator cap off, start the engine, and let it idle. As it warms up, you’ll see air bubbles coming out of the radiator neck. Keep topping off the coolant as the level drops. Once the bubbles stop and the thermostat opens (you’ll see the coolant start to circulate), the system is burped. Shut it off and install the cap.
- Step 6: Clear the Code. Use your OBD-II scanner to clear the code. If you don’t have one, disconnecting the battery for 15 minutes will usually do the trick. Take it for a test ride to confirm the check engine light stays off.
P0118 Best Practices and Long-Term Care Guide
Preventing this code from coming back involves a few simple habits. These polaris engine code p0118 best practices focus on protecting your machine’s sensitive electronics.
After a particularly muddy or wet ride, take a moment to visually inspect key sensor connections like the ECT. Gently rinse away heavy mud buildup rather than hitting it with a high-pressure washer, which can force water into connectors.
For added protection in harsh environments, consider applying a small amount of dielectric grease to the inside of the connector. This helps seal out moisture and prevent corrosion.
Finally, think of fixing this code as a key part of your machine’s health. Promptly addressing a P0118 code is an eco-friendly polaris engine code p0118 practice. You’ll stop wasting fuel and reduce harmful emissions from an engine running too rich. A healthy engine is a sustainable polaris engine code p0118 solution for years of reliable riding.
Frequently Asked Questions About Polaris Engine Code P0118
Can I still ride my Polaris with a P0118 code?
It’s not a great idea. While it probably won’t cause immediate, catastrophic damage, you’ll suffer from very poor performance, terrible fuel economy, and could potentially foul your spark plugs over time. More importantly, if the fan isn’t working correctly, you risk a serious overheating event.
How much does it cost to fix a P0118 code?
This is one of the best benefits of polaris engine code p0118—it’s cheap to fix! If you do it yourself, you’re only looking at the cost of a new ECT sensor (typically $20-$60) and a little coolant. If you take it to a shop, you can expect to pay for the part plus 1-1.5 hours of labor, likely totaling $150-$300.
Is the ECT sensor the same as the temperature sending unit for the gauge?
Often, no. Many machines use two separate sensors. The ECT sensor talks exclusively to the ECU to control engine functions. A second, single-wire temperature sending unit usually operates the gauge on your dashboard. A P0118 code is specific to the sensor the ECU reads.
What if I replace the sensor and the code comes back immediately?
If the code returns right away, it strongly suggests the problem isn’t the sensor but the wiring harness. Go back to Step 4 of the diagnosis and perform a thorough check of the wires for a break or a short circuit. This is where patience pays off.
Tackling a check engine light can feel daunting, but the polaris engine code p0118 is a perfect place to build your confidence as a DIY mechanic. By following these steps, you can save money, learn more about your machine, and gain the satisfaction of fixing it yourself.
Now that you have the knowledge and the plan, you’ve got this. Get it fixed, clear that code, and get back out on the trail where you belong. Ride safe!
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