How to Diagnose and Fix a Failing Ignition Coil in Your 2020 Accord

How to Fix Ignition Coil Issue

For 2020 Honda Accord owners, a failing ignition coil can manifest as a confusing array of symptoms, often leading to misdiagnosis. While not a widespread epidemic, it is a documented failure point that can cause significant drivability issues. The fix, however, is often straightforward and relatively inexpensive. As one owner shared their experience: "Only issue so far after 135K miles it was a damaged ignition coil which at first I thought I had the infamous blown head gasket, but after taking my car to my local mechanic, he fixed it for $120." This guide will walk you through identifying, diagnosing, and resolving this specific problem based on real owner experiences.

Symptoms

The symptoms of a failing ignition coil in your vehicle can range from subtle to severe, and they often mimic other, more serious engine problems. The most common report from owners is a misfire. This feels like a shuddering, jerking, or hesitation during acceleration, especially under load. You might feel the engine stumble or hear a sputtering sound from the exhaust. The check engine light will almost certainly illuminate, and a code reader will typically show a cylinder-specific misfire code (e.g., P0301 for cylinder 1).

Another critical symptom is stalling. A weak or intermittent coil can cause the engine to cut out unexpectedly, particularly at idle or when coming to a stop. This is not only inconvenient but can be a serious safety hazard. In more advanced cases, the problem can lead to a no-start condition. If the coil fails completely, it cannot generate the spark needed to ignite the air-fuel mixture, leaving you stranded. One owner's experience highlights the confusion these symptoms can cause, initially suspecting a catastrophic failure: "which at first I thought I had the infamous blown head gasket."

Less direct but related symptoms mentioned by owners in broader electrical troubleshooting include issues with warning lights. While not directly caused by the coil itself, chasing electrical gremlins requires a systematic approach. As one owner detailed while diagnosing a brake lamp warning: "I’ve replaced all bulbs, the tail light failure sensor, the brake switch, the brake pedal stopper pad, and checked all the grounds. Light turns on as soon as the brake pedal is depressed for the first time once ignition is in on position." This meticulous process is the same mindset needed for diagnosing an ignition fault—checking each component in the system.

Most Likely Cause

The primary cause of ignition coil failure in this context is age-related wear and internal breakdown. Ignition coils are robust electronic components, but they operate in a harsh environment. They are subjected to extreme heat cycles from the engine, constant vibration, and exposure to moisture and road contaminants. Over time, typically after many miles of service, the internal windings and insulation can degrade. This degradation leads to a weaker spark or a complete loss of the ability to transform the battery's low voltage into the thousands of volts needed to fire the spark plug.

It is crucial to distinguish this from other potential causes. Owner data does not point to a systemic design flaw or a common ancillary part failure causing the coils to die prematurely. For instance, while a clogged air filter can cause performance issues, it is not cited as a direct cause of coil failure in the provided experiences. The failure is isolated to the coil itself as a wear item. The mechanic's diagnosis for the owner who paid $120 was simply a "damaged ignition coil," indicating a straightforward component failure.

How to Diagnose

Diagnosing a faulty ignition coil requires a methodical approach, starting with the simplest checks. You will need an OBD2 code scanner. This is an essential tool for any modern car owner. Connect the scanner to the port under the dashboard, turn the ignition to the "ON" position (without starting the engine), and read the stored diagnostic trouble codes (DTCs). A code starting with P0300 (random misfire) or P0301-P0304 (cylinder-specific misfire) is your strongest initial clue.

The next step is a process of elimination focused on the ignition system for the flagged cylinder. The basic components are the spark plug, the ignition coil, and the wiring. A visual inspection can sometimes reveal obvious issues like corrosion on the coil's electrical connector or physical damage. With the engine running (if possible), carefully listen for arcing sounds near the coils, which indicate electricity jumping to ground. You can also use a spray bottle with water to mist the coils and wires; arcing will become more audible and visible in the dark, but exercise extreme caution.

A more definitive test is the swap test. If your code points to Cylinder 2, for example, you can swap the ignition coil from Cylinder 2 with the coil from Cylinder 3. Clear the codes with your scanner, drive the vehicle until the check engine light returns, and scan again. If the misfire code now follows the coil to Cylinder 3 (e.g., changes from P0302 to P0303), you have confirmed the coil is faulty. If the code stays at P0302, the problem is likely the spark plug or an issue with that specific cylinder (like low compression or an injector problem). This logical diagnostic approach mirrors the troubleshooting described for other electrical issues: "If it stops coming on the issue is the ignition switch or short inbetween switch and that fuse. If still on check the circuit on other side of that fuse."

Step-by-Step Fix

Replacing a faulty ignition coil is one of the more accessible DIY repairs. Here is a detailed guide based on standard mechanical procedures for this engine.

1. Gather Tools and Parts: Ensure you have the correct replacement coil(s), a spark plug socket (usually 5/8" or 16mm) with a long extension and ratchet, a 10mm socket for the coil bolt, and your OBD2 scanner. Disconnect the negative battery terminal for safety.
2. Locate and Expose the Coils: Open the hood and locate the engine cover. It is typically held by rubber grommets or clips; lift it straight up to remove. You will now see the four ignition coils mounted on the valve cover, each with an electrical connector.
3. Remove the Faulty Coil: Identify the coil corresponding to the misfiring cylinder. Firmly press the tab on the electrical connector and pull it straight off. Using your 10mm socket, remove the single bolt securing the coil to the valve cover.
4. Extract the Coil and Spark Plug: Grasp the coil firmly and pull it straight up with a steady, rocking motion. It is sealed with a rubber boot; it may require some force to break free. Once the coil is out, you can inspect the spark plug well for oil or debris—a sign of other issues like a leaking valve cover gasket. It is highly recommended to replace the spark plug while you have access. Insert your spark plug socket and extension into the well, attach the ratchet, and turn counterclockwise to remove the old plug.
5. Install New Spark Plug: Carefully thread the new spark plug in by hand to avoid cross-threading. Once hand-tight, use the ratchet and socket to tighten it to the manufacturer's specification (typically about 13-20 ft-lbs for these engines; consult a service manual for the exact torque).
6. Install New Ignition Coil: Before installing the new coil, apply a small amount of dielectric grease to the inside of the rubber boot that contacts the spark plug. This aids future removal and seals out moisture. Push the new coil down into the well firmly until it seats completely on the spark plug. Reinstall the 10mm mounting bolt and reconnect the electrical connector until it clicks.
7. Repeat if Necessary: If replacing multiple coils, repeat steps 3-6 for each one.
8. Reconnect and Test: Reinstall the engine cover and reconnect the negative battery terminal. Use your OBD2 scanner to clear all diagnostic trouble codes. Start the engine. It may run roughly for a few seconds as the computer relearns. Listen for smooth operation. Take the car for a test drive to ensure the misfire and hesitation are gone.

As one owner confirmed after a professional repair, the result is a complete fix: "he fixed it for $120." The process, whether DIY or professional, targets the failed component directly.

Parts and Tools Needed

• Replacement Ignition Coil(s): It is advisable to use OEM or high-quality aftermarket coils (e.g., Denso, NGK, which are often OEM suppliers). While owners have asked about aftermarket parts for other components—"And if they are aftermarket what brand and where to find them?"—for critical ignition parts, sticking with known quality is best. Replace all four if mileage is high or budget allows, but replacing just the faulty one is acceptable.
• Spark Plugs (Recommended): NGK or Denso Iridium plugs, specified for the 1.5L Turbo engine. Replacing the plug when replacing the coil is standard practice.
• Basic Socket Set: Including a 10mm socket for the coil bolt.
• Spark Plug Socket: 5/8" (16mm) with a magnetic insert or rubber holder to grip the plug, and a long extension (6-inch minimum).
• Ratchet
• Dielectric Grease: A small tube for the coil boot.
• OBD2 Code Scanner: Essential for reading and clearing codes.
• Torque Wrench (Recommended): For proper spark plug installation.

Real Owner Costs

The cost to fix an ignition coil issue varies significantly between DIY and professional repair, and the provided owner data gives a clear snapshot.

• Professional Repair Example: The most direct cost report comes from an owner who had a mechanic handle the job: "he fixed it for $120." This likely represents the cost for a single coil replacement, including parts and labor at an independent shop. At a dealership, this cost could easily be $200-$300 for the same repair.
• DIY Cost Breakdown: Doing it yourself dramatically reduces cost. A single high-quality aftermarket ignition coil can cost between $40 and $80. A set of four iridium spark plugs costs approximately $40-$60. If you already own the basic tools, your total parts cost for one coil and one plug would be around $50-$90. Even if you purchase a decent OBD2 scanner for $50, your total investment ($100-$140) is comparable to the single professional repair cost, and you keep the tools for future use.
• Cost of Misdiagnosis: The owner's quote highlights an indirect cost—worry and misdiagnosis. Thinking it was a "blown head gasket" implies they were mentally preparing for a repair costing well over $1,000. Proper diagnosis, therefore, saves not just money but significant stress.

Prevention

While ignition coils are ultimately wear items, you can take steps to prolong their life and catch issues early. The main enemy of electrical components is heat and moisture. Ensuring your engine's cooling system is functioning properly helps manage under-hood temperatures. Avoid spraying water directly onto the engine bay during washing. Regularly scheduled maintenance, including timely spark plug replacement as specified in your manual (often around 60,000-100,000 miles for iridium plugs), reduces the stress on the coils. A worn spark plug requires a higher voltage to fire, straining the coil.

Furthermore, pay attention to small changes in how your car runs. That slight hiccup during acceleration or a barely perceptible rough idle is your first warning sign. Addressing a single misfire promptly can prevent the unburned fuel from damaging the catalytic converter—a repair that makes a coil replacement look trivial by comparison. As with any electrical component on the car, from headlight bulbs to sensors, proactive attention is key. An owner noted how easy it is to miss a small failure: "you won’t know until you have the ignition on and it’s dark enough to see that it no longer lights up."

What Owners Say

Real experiences from HONDA owners:

Success Stories

"Only issue so far after 135K miles it was a damaged ignition coil which at first I thought I had the infamous blown head gasket, but after taking my car to my local mechanic, he fixed it for $120." — Geek508 ($120) (source)

"I got a 1.5T, I drive 80% highway with Eco mode all the time, gives me 500 miles per tank. Only issue so far after 135K miles it was a damaged ignition coil which at first I thought I had the infamous blown head gasket, but after taking my car to my local mechanic, he fixed it for $120." — Geek508 ($120) (source)

Owner Experiences

"I’ve replaced all bulbs, the tail light failure sensor, the brake switch, the brake pedal stopper pad, and checked all the grounds. Light turns on as soon as the brake pedal is depressed for the first time once ignition is in on position." — NegotiationAlive9589 (source)

"there’s one tiny bulb in there. And all you have to do is change the radio on these cars where that needs to be popped out-and that fragile little bulb's filament, with some age on it, typically fails." — HotRodHomebody (source)

"And you won’t know until you have the ignition on and it’s dark enough to see that it no longer lights up. Super easy to replace the bulb, the dealer stocks it." — HotRodHomebody (source)

Lessons Learned

⚠️ "The BRAKE LAMP warning has to do with the brake bulbs/circuit. I’ve replaced all bulbs, the tail light failure sensor, the brake switch, the brake pedal stopper pad, and checked all the grounds." — NegotiationAlive9589 (source)

⚠️ "I doubt it will be the start button, as you seem to still get it to reliably go into accessories and ignition modes - just not the start function. If you had to keep pressing it to get into accessories, then I would suspect the start button." — commodorenut (source)

⚠️ "It is very likely to be the culprit based on everything else you have done. I doubt it will be the start button, as you seem to still get it to reliably go into accessories and ignition modes - just not the start function." — commodorenut (source)

Pro Tips from Owners

💡 "After the 5 minutes, try starting the car, if it doesn’t start you need a battery. Make sure you have a battery on standby lol" — Outrageous-Context78 (source)

💡 "You can test by using a test light to manually ground the relay and you should hear the pump come on. It that’s all good then you need to check the control side." — nickandre (source)

💡 "If you don’t get power, check the power and fuse for the load side of relay and then check for control side input. You can test by using a test light to manually ground the relay and you should hear the pump come on." — nickandre (source)

Real Repair Costs

"Very noticable if you turned the key slow from the second position to where the starter engages. Its a very cheap part $25-$50 takes about a hour to install." — moey (source)

FAQ

Q: How long does it take to replace an ignition coil? A: For a DIYer with basic tools and some mechanical confidence, replacing a single ignition coil and its corresponding spark plug takes about 30 to 60 minutes. This includes time for diagnosis (scanning and clearing codes) and careful reassembly. A professional mechanic can typically complete the job in under 30 minutes.

Q: Can I drive my Accord with a misfiring ignition coil? A: It is strongly discouraged. Driving with a severe misfire can cause permanent damage. Unburned fuel can be dumped into the exhaust system, overheating and destroying the catalytic converter—a very expensive part to replace. It can also lead to engine stalling, which is a safety hazard. If the misfire is very minor and intermittent, you might drive it cautiously to a repair shop, but this is a risk.

Q: Is a failed ignition coil a common issue on the 2020 Accord? A: Based on the available owner data, it is not described as a widespread, chronic failure. It appears as a standard age- and mileage-related repair. One owner experienced it at 135,000 miles, which is a reasonable service interval for this component. It is not indicative of a model-wide defect.

Q: Should I replace all four coils if one fails? A: It is not strictly necessary, but it is often recommended, especially at higher mileage. If one coil has failed due to age, the others are operating under the same conditions and may be nearing the end of their service life. Replacing all four ensures uniform performance and prevents you from having to repeat the repair in the near future. It is a cost-benefit decision; replacing just the faulty one is a perfectly valid fix.

Q: DIY vs mechanic—what's recommended for this repair? A: This repair is very well-suited for a competent DIYer. The steps are straightforward, no specialized tools are required beyond a basic socket set and code scanner, and the risk of causing further damage is low if you follow instructions. The significant cost savings is a major benefit. However, if you are uncomfortable working under the hood, the professional cost (around $120 as reported) is reasonable for the peace of mind and warranty on the work.

Q: Will a bad ignition coil always trigger a check engine light? A: In virtually all cases, yes. The engine control module (ECM) is very sensitive to misfires and will detect the irregular combustion almost immediately, storing a code and illuminating the check engine light. A pending code may be stored even before the light comes on, which is why an OBD2 scanner is the first diagnostic step.