Why Your 2020 Ford Explorer Check Engine Light Is On (And How to Fix It)

How to Fix Check Engine Light

A check engine light on your 2020 Ford Explorer is a call to action, not a cause for panic. It’s the vehicle's primary way of telling you its computer has detected a fault in the engine, transmission, or emissions system. While the light can indicate anything from a loose gas cap to a serious mechanical issue, ignoring it is never advisable, as it can lead to reduced performance, lower fuel economy, or significant damage. The key is a methodical diagnosis to understand what specific problem the truck is reporting. As one owner shared while troubleshooting: "I’m currently waiting on a buddy for a code reader to see what code is being thrown but could anybody give some insight on what it possibly could be? ChatGPT seems to think it’s possibly the thermostat but I don’t consider that to be a definitive answer" (source). This highlights the critical first step: retrieving the diagnostic trouble code (DTC) before guessing at solutions.

Symptoms

The check engine light itself is the primary symptom, but it is almost always accompanied by other warning signs that give clues to the underlying problem. Owners report a range of secondary symptoms that help narrow down the issue. A very serious combination reported involves overheating and a severe loss of power. One driver experienced this directly: "2020 Ford Explorer XLT overheating with check engine light on So woke up this morning to get ready for work, turned on my car about 10-15 minutes before I left and when I got back in it said the car was overheating, the check engine light was on and when I tried to drive it was in limp mode" (source). "Limp mode" is a protective state where the vehicle's computer drastically reduces engine power to prevent damage, often triggered by overheating or other critical faults.

In less severe cases, you may not notice any immediate change in how the truck drives. The light can illuminate for an emissions-related fault that doesn't impact drivability in the short term, such as a small vacuum leak or a failing sensor. However, prolonged driving with even a minor fault can cause other issues, like rough idling, a slight drop in fuel economy, or hesitation during acceleration. It's also common for the vehicle to store the fault in memory, which can cause it to fail an emissions inspection even if the light turns off temporarily.

Another symptom to be aware of is the light's behavior. A solid, steady check engine light typically indicates a non-critical fault that should be investigated soon. A flashing check engine light is a major warning that signifies a severe misfire that can damage the catalytic converter due to unburned fuel entering the exhaust system. If you see a flashing light, you should reduce engine load and seek diagnosis immediately. The symptoms are your first data point, guiding you toward the urgency and potential area of the problem.

Most Likely Cause

Based on owner discussions and common automotive principles for this platform, one of the most frequent triggers for a check engine light in the 2020 Ford Explorer is a vacuum leak. The engine relies on a sealed vacuum system for numerous functions, including controlling the airflow that bypasses the throttle plate (idle air control), managing emissions devices like the purge valve, and ensuring the proper air-fuel ratio. A leak introduces unmetered air into the intake manifold, confusing the engine computer (PCM).

The PCM uses data from the Mass Air Flow (MAF) sensor to determine how much air is entering the engine and then calculates the correct amount of fuel to inject. A vacuum leak allows extra air to sneak in after the MAF sensor has already measured the airflow. This results in a "lean" condition (too much air, not enough fuel). The oxygen sensors in the exhaust detect this lean mixture and report it back to the PCM, which then triggers a check engine light with codes like P0171 (System Too Lean Bank 1) or P0174 (System Too Lean Bank 2). While other issues like a failing thermostat (as suspected in the owner quote) or oxygen sensor can also illuminate the light, vacuum leaks are a prevalent and often elusive culprit that requires careful diagnosis.

How to Diagnose

Diagnosing a check engine light properly requires a systematic approach, starting with the simplest step. You absolutely must begin by reading the diagnostic trouble codes (DTCs). This requires an OBD-II scanner. You can use a basic code reader, a more advanced Bluetooth scanner that pairs with a smartphone app (like Torque Pro or FORScan Lite), or have an auto parts store read it for free. The code, such as P0128 (Coolant Thermostat Rationality) for a thermostat issue or P0171 for a lean condition, is your roadmap. As the owner noted, guessing without the code is inefficient: waiting for a code reader is the correct first move.

Once you have the code, research its specific meaning for your 2020 Explorer. For a suspected vacuum leak (lean code), the next step is a visual and auditory inspection. With the engine running, listen carefully around the engine bay for a distinct hissing or sucking sound, which is a telltale sign of a leak. Pay close attention to vacuum hoses, the intake manifold gaskets, the brake booster line, and the PCV valve and its hose. Visually inspect all rubber vacuum lines for cracks, dryness, brittleness, or connections that have popped off.

If a visual inspection doesn't reveal the leak, you can perform a smoke test. This is the most definitive method for finding vacuum and intake leaks. A smoke machine introduces non-toxic, visible smoke into the intake system. With the engine off, the smoke will seep out of any leak points, clearly showing you the problem area. While professional shops have commercial smoke testers, affordable DIY smoke testers can be made or purchased. For overheating-related codes, diagnosis involves checking coolant levels, verifying the operation of the thermostat, and ensuring the cooling fans and water pump are functioning correctly.

Step-by-Step Fix

The repair steps depend entirely on the diagnosed cause. Here is a step-by-step guide for addressing a common vacuum leak, which often involves replacing a cracked or degraded vacuum hose.

1. Retrieve and Record Codes: Use your OBD-II scanner to pull all stored codes. Write down the exact code(s) (e.g., P0171) and any freeze frame data.
2. Locate the Vacuum Diagram: Often found on a sticker under the hood or in the owner's manual. This diagram maps the routing of all vacuum hoses and is essential for correct reassembly.
3. Identify the Faulty Component: Based on your visual inspection or smoke test, identify the specific leaking hose, gasket, or valve. Common culprits are the PCV valve hose, the brake booster line, or the hose connecting to the intake manifold.
4. Gather Correct Replacement Parts: Visit a dealership or auto parts store with your vehicle's VIN to ensure you get the exact hose or gasket. Do not guess on the diameter or shape.
5. Disconnect the Battery (Safety First): Disconnect the negative battery terminal to prevent any electrical issues while working.
6. Remove the Old Hose/Component: Use pliers if necessary to loosen spring clamps or squeeze tab-style clamps. Gently twist and pull the hose off its fitting. If it's brittle, it may break.
7. Clean the Fittings: Use a clean rag to wipe the metal or plastic nipples where the hose attaches. Ensure they are free of old rubber residue and dirt.
8. Install the New Hose: Slide the new hose onto the fitting. Ensure it is seated fully and securely. Reattach the clamps in their original positions.
9. Reconnect the Battery: Reconnect the negative battery terminal.
10. Clear Codes and Test Drive: Use your scanner to clear the check engine light codes. Start the engine and let it idle, listening for any remaining hissing. Take the vehicle for a test drive of at least 10-15 minutes, including various engine loads (city and highway), to allow the computer to complete its drive cycle and verify the light does not return.

For a thermostat replacement (a common fix for overheating and related codes like P0128), the process is more involved, requiring draining the coolant, removing the thermostat housing, replacing the thermostat and often the gasket, refilling, and bleeding the cooling system of air. This job is more complex due to the need to handle coolant and ensure no air pockets remain, which can lead to further overheating.

Parts and Tools Needed

The parts and tools vary by repair. For a vacuum leak fix:

• Parts: Specific vacuum hose(s) or intake manifold gasket set. Parts should be sourced using your VIN. An OEM thermostat assembly (often includes gasket) is needed for that repair.
• Tools:
  • OBD-II Code Scanner (Essential for diagnosis and reset)
  • Basic Socket and Wrench Set
  • Pliers (for hose clamps)
  • Flashlight
  • Safety Glasses
  • Optional but Recommended: DIY smoke tester or professional smoke test service.

For a thermostat job, add:

• Parts: New thermostat, new coolant (meeting Ford specification WSS-M97B57-A2), thermostat housing gasket or O-ring.
• Tools: Drain pan, funnel, jack and jack stands (if needed for access), torx or socket drivers for housing bolts.

Real Owner Costs

Repair costs can vary dramatically based on the cause and whether you perform the work yourself or use a professional. For a simple vacuum hose replacement, the part may cost between $20 and $80. If you do it yourself, that's the total cost. At a shop, you'd pay for the part plus labor. As one owner commented on general repair rates, "It sucks being old! $160 an hour is highway robbery. You might wanna check your local Ford dealership and try to poach one of their mechanics for after hours work" (source). At a rate of $160/hour, a shop might charge 0.5 to 1 hour of labor for diagnosing and replacing a hose, leading to a total bill of $100 to $240.

For a more complex job like a thermostat replacement, the part cost is similar ($50-$150), but the labor time is significantly higher—often 2 to 3 hours due to coolant drain/refill and bleeding procedures. This could result in a shop bill ranging from $370 to $630. These costs underscore the value of an accurate initial diagnosis; paying for a diagnostic fee (often $100-$150) can save you thousands by pinpointing the exact issue instead of replacing parts based on a guess.

Prevention

Preventing check engine lights involves consistent, proactive maintenance. Regularly inspect engine bay components, especially rubber parts like vacuum hoses and coolant hoses, for signs of wear, cracking, or brittleness. This is particularly important as the vehicle ages and is exposed to heat cycles. Adhere strictly to the factory-recommended maintenance schedule for coolant flushes, which can prevent thermostat housing corrosion and failure. Using a high-quality OBD-II scanner periodically, even when no light is on, to check for "pending" codes can alert you to a developing problem before it triggers the full light. Finally, always address a check engine light promptly. A small, inexpensive leak or sensor fault can, if ignored, lead to catalyst damage or engine overheating, resulting in repairs that cost thousands.

What Owners Say

Real experiences from FORD owners:

Owner Experiences

"I drive for work all highway and I got 150k out of my stock brakes on a 2020 exploder" — bklipa88 (source)

"I need to get a car (used is all I can afford). On paper, I really like ford explores (2010s- 2020)." — smokeyflamingo (source)

"On paper, I really like ford explores (2010s- 2020). I’ve never even test driven one but it seems to have all the things I’m looking for." — smokeyflamingo (source)

Real Repair Costs

"We'll probably be spending around $30K and putting around $10-15K down. We can always put it on the line of credit if that's the cheaper rate, just want to hear what's out there." — NoPlum8970 (source)

"It sucks being old! $160 an hour is highway robbery. You might wanna check your local Ford dealership and try to poach one of their mechanics for after hours work." — Combatvet (source)

FAQ

Q: How long can I drive with the check engine light on? A: It depends on the symptom. If the light is solid and you notice no changes in performance, temperature, or strange noises, it's likely safe to drive for a short period to get it diagnosed. However, if the light is flashing, or if you have any secondary symptoms like overheating, loss of power, or severe rough idle, you should stop driving immediately to avoid causing catastrophic engine or catalytic converter damage. The owner who experienced overheating and limp mode was right not to drive it normally.

Q: Is a check engine light a common issue on the 2020 Explorer? A: While not necessarily "common" as a universal fault, the 2020 Explorer, like any modern vehicle with complex emissions and engine management systems, is susceptible to the typical issues that trigger the light. Owner discussions frequently point to emissions-related faults (like vacuum leaks) and cooling system components (like thermostats) as recurring themes. Its prevalence is more about the complexity of modern cars than a specific defect in this model year.

Q: Should I try to fix a check engine light myself or take it to a mechanic? A: This depends on your skill level, tools, and the diagnosed cause. Retrieving the code is a simple DIY task anyone can learn. Replacing a visibly cracked vacuum hose is also very straightforward. More complex issues, like an internal vacuum leak at an intake manifold gasket, a failing thermostat, or electrical sensor problems, often require more advanced mechanical knowledge, special tools, and time. If you are unsure after reading the code, consulting a professional for diagnosis is a wise investment. As one owner seeking help noted, leveraging a community or a professional for insight is a smart approach.

Q: Will the check engine light turn off by itself if the problem goes away? A: Sometimes, but not reliably. If an intermittent issue (like a temporary sensor glitch) resolves, the PCM may turn the light off after a certain number of successful drive cycles without detecting the fault. However, the diagnostic trouble code (DTC) will remain stored in the computer's memory as a "pending" or "history" code. For a confirmed, persistent problem, the light will stay on until the issue is fixed and the codes are manually cleared with a scanner.

Q: Can a loose gas cap cause the check engine light in my Explorer? A: Absolutely. The fuel system is designed to be sealed. A loose, damaged, or missing gas cap can cause a small leak in the evaporative emissions (EVAP) system, triggering a code (often P0455 or P0457). This is one of the simplest and most common causes. Always ensure your gas cap is tightened securely until it clicks three times. If the light came on after refueling, this should be your first check.

Q: How much does a professional diagnosis usually cost? A: Most independent repair shops and dealerships charge a diagnostic fee, typically ranging from $100 to $175. This fee is usually applied toward the total repair cost if you have the work done at that shop. Some auto parts stores offer free code reading, but this is only the first step; true diagnosis involves pinpoint testing beyond just retrieving the code, which is what the diagnostic fee covers.