How to Test a Bad Ignition Coil on Cylinder 2: Symptoms and Diagnosis

If your engine is shaking, your check engine light is flashing, and you've narrowed the problem down to cylinder 2, testing the ignition coil is one of the smartest first steps you can take. A bad coil on cylinder 2 causes misfires, rough idling, poor fuel economy, and can damage your catalytic converter if you ignore it. The good news is that you don't need a shop to figure out if the coil is the problem. With basic tools and about 20 minutes, you can test it yourself in your driveway.

What does an ignition coil on cylinder 2 actually do?

An ignition coil converts your car's 12-volt battery power into the high voltage (around 25,000–45,000 volts) needed to create a spark at the spark plug. On most modern engines, each cylinder has its own coil called a coil-on-plug (COP) setup. Cylinder 2's coil sits directly on top of cylinder 2's spark plug. When it fails, that specific cylinder stops firing correctly, and you'll feel it as a misfire.

The coil receives a signal from the engine control module (ECM), which tells it exactly when to fire. If the coil windings are damaged, cracked, or shorted, the voltage drops or disappears entirely. That means the air-fuel mixture in cylinder 2 doesn't ignite, or ignites weakly.

What symptoms point to a bad coil on cylinder 2 specifically?

Before you grab your tools, make sure the symptoms actually match a cylinder 2 coil problem. You can learn more about the specific signs of a misfire on cylinder 2 only, but here are the most common ones:

Check engine light with a P0302 code This is the misfire code specific to cylinder 2. A generic scanner will pull this code and tell you exactly which cylinder is affected.
Rough idle or engine vibration You may feel the car shaking more than usual at a stoplight, especially with your hand on the steering wheel or gear shifter.
Lack of power under acceleration The engine stumbles or hesitates when you press the gas pedal.
Reduced fuel economy The ECM tries to compensate for the misfiring cylinder by adjusting fuel trim, which wastes gas.
Rotten egg smell from the exhaust Unburned fuel entering the catalytic converter can produce a sulfur smell.

How do you test the ignition coil on cylinder 2 with a multimeter?

A multimeter is the most accessible tool for checking whether a coil is electrically sound. You're measuring resistance (ohms) across the coil's windings. If the readings are outside the manufacturer's spec, the coil is bad. For a detailed walkthrough of multimeter readings, see our guide on what multimeter readings to expect from a cylinder 2 coil.

Step 1: Remove the coil from cylinder 2

Disconnect the electrical connector from the coil by pressing the release tab and pulling it off. Then remove the bolt (usually a 10mm) that holds the coil bracket in place. Pull the coil straight up and out of the spark plug well. Be careful not to damage the rubber boot at the bottom if it tears, debris can fall into the cylinder.

Step 2: Set your multimeter to ohms

Turn the dial to the resistance (Ω) setting. You'll be testing two things: the primary winding resistance and the secondary winding resistance.

Step 3: Test primary resistance

Place one multimeter probe on each of the coil's two electrical terminals (the pins where the connector plugs in). A healthy coil-on-plug unit typically reads between 0.5 and 2.0 ohms for primary resistance, though specs vary by vehicle. Check your service manual for exact numbers.

Step 4: Test secondary resistance

Place one probe on one of the electrical terminals and the other probe inside the spring contact at the bottom of the coil (where it connects to the spark plug). A good coil usually reads between 6,000 and 15,000 ohms (6–15 kΩ). Again, confirm with your specific vehicle's specs.

Step 5: Compare your readings

If either reading is way above, way below, or showing "OL" (open loop/infinite resistance), the coil is bad and needs replacement. A reading of zero means there's a short inside the coil.

Can you swap the coil to confirm it's the problem?

Yes and this is one of the fastest, most reliable ways to confirm a bad coil without a multimeter. Here's how it works:

Remove the coil from cylinder 2.
Swap it with the coil from another cylinder (say, cylinder 1).
Clear the trouble codes with your OBD-II scanner.
Start the engine and let it run for a minute or two.
Scan again for codes.

If the misfire follows the coil meaning you now get a P0301 code for cylinder 1 the coil is confirmed bad. If the misfire stays on cylinder 2 (P0302 again), the coil isn't the issue, and you should look at the spark plug, fuel injector, or compression. This swap test is covered in more detail in our article on how to test a bad ignition coil on cylinder 2.

What if the coil tests good but you still have a misfire on cylinder 2?

A coil that tests within spec on a multimeter can still occasionally fail under load. More commonly, though, the problem is elsewhere. Here are the other parts to check:

Spark plug Pull the plug from cylinder 2 and inspect it. Look for a worn electrode, heavy carbon deposits, oil fouling, or a cracked porcelain insulator. A bad spark plug is one of the most common causes of a cylinder-specific misfire.
Spark plug boot or connector Check the rubber boot on the coil for cracks or carbon tracking (black lines that let voltage leak). Also check the electrical connector for corroded or bent pins.
Fuel injector A clogged or dead injector on cylinder 2 will cause the same misfire symptoms as a bad coil. You can test it with a multimeter (typical resistance: 11–18 ohms) or use a mechanic's stethoscope to listen for clicking.
Compression Low compression from a leaking valve or worn piston rings will cause a persistent misfire that no coil or plug swap will fix. A compression test will rule this out.
Wiring and ECM In rare cases, damaged wiring between the ECM and the coil connector, or a faulty ECM driver circuit, is the cause. Check for damaged or chafed wires before replacing the ECM.

What are the most common mistakes people make when testing an ignition coil?

Replacing the coil without testing first Throwing parts at a problem wastes money. A $15 spark plug might be the real fix, not a $60–$150 coil.
Not clearing codes after a swap test If you don't clear the old codes before running the engine, your scanner will still show the old P0302, and you won't know if the misfire moved.
Ignoring the spark plug Always pull and inspect the plug when you remove the coil. Plug condition tells you a lot about what's happening inside that cylinder.
Cross-threading the coil bolt or damaging the boot Reinstall the coil carefully. A torn boot lets moisture and debris into the spark plug well.
Using generic resistance specs Different coil manufacturers use different winding specs. A reading that's "normal" for a Toyota coil might be out of range for a Ford. Always check your vehicle's service manual or manufacturer spec sheet.

How much does a replacement cylinder 2 ignition coil cost?

A single ignition coil typically costs between $30 and $150, depending on the make and model. OEM (original equipment manufacturer) coils cost more than aftermarket, but they tend to last longer and cause fewer issues. Labor at a shop is usually minimal 0.3 to 0.5 hours since the coil is easy to access on most engines. If you're doing it yourself, you'll spend nothing on labor.

Some mechanics recommend replacing all coils at once if the vehicle has high mileage, since they tend to fail around the same age. That said, if the other coils are testing fine and your budget is tight, replacing just the bad one is perfectly reasonable.

Practical checklist: testing a bad ignition coil on cylinder 2

Pull the trouble code with an OBD-II scanner. Confirm it's P0302 (cylinder 2 misfire).
Inspect visually Look at the coil, boot, and connector for cracks, carbon tracking, corrosion, or oil contamination.
Swap test Move the cylinder 2 coil to another cylinder, clear codes, run the engine, and re-scan. If the misfire follows the coil, it's bad.
Multimeter test Measure primary and secondary resistance and compare to manufacturer specs.
Check the spark plug while the coil is out inspect for wear, fouling, or damage.
Replace if confirmed bad Install the new coil, reconnect the electrical connector, torque the bolt, and clear the codes.
Test drive Drive the car under normal conditions. Re-scan after 20–30 miles to make sure no codes return.

Quick tip: If you're not sure whether it's the coil or the spark plug causing the misfire, replace the spark plug first it's cheaper and often the actual problem. If the misfire continues, then test or replace the coil.