How to Measure an Ignition Coil?
3 Answers
Measuring an ignition coil involves the following steps: 1. Turn the vehicle's ignition switch to the "ON" position. Then unplug the ignition coil connector, use one end of a multimeter to measure pin 3 and the other end to measure the ground wire. If the voltage between the pin and ground is around 12V, proceed to the next step; if not, check the wiring. 2. Unplug the ignition coil connector, use one end of the multimeter to measure pin 1 and the other end to measure pin 5# of the ECU to check for any short circuits or open circuits. If any are found, inspect the wiring; if not, proceed to the next step. 3. Unplug the ignition coil connector, use one end of the multimeter to measure pin 2 and the other end to measure pin 2# of the ECU to check for any short circuits or open circuits. If any are found, inspect the wiring; if not, proceed to the next step. 4. Use the multimeter to measure whether the resistance of the sensor's primary coil is 0.9Ω. If it is, proceed to the next step; if not, replace the ignition coil. 5. Use the multimeter to measure whether the resistance of the sensor's primary coil is 14.5Ω. If it is, proceed to the next step; if not, replace the ignition coil.
Measuring the ignition coil isn't actually difficult, I often do it myself. First, you need a multimeter, which is the tool for measuring resistance values. Turn off the engine and remove the key for safety. Then, disconnect the plug from the ignition coil, set the multimeter to the resistance range, and use the probes to touch the two terminals of the coil to measure the primary resistance; if the value is around 0.4 to 2 ohms, it's generally fine. Next, measure the secondary resistance, which requires touching the center hole of the coil and the other terminal, with resistance values typically between 5000 and 15000 ohms considered normal. If the value fluctuates wildly or shows infinity, it means the coil is bad. Remember, standards vary by car model, so it's best to check the owner's manual for reference. A faulty ignition coil can cause rough idling or poor acceleration, so checking early can save money and hassle. The tools are cheap—a multimeter costs just a few tens of dollars—and remember to wear gloves to prevent electric shock before starting.
Hey, I've got plenty of experience testing ignition coils. When my old car had issues, I'd simply measure resistance with a multimeter: for the primary coil connected to the input terminal, anything over 2 ohms might indicate a problem; for the secondary coil, check if the high-voltage side exceeds 10,000 ohms. But resistance alone isn't enough—I'd also do a spark test. Hook up an old spark plug to the ignition coil, place it on the engine cover (don't touch it with your body), then start the engine to see if the spark is blue and steady. If it's red or there's no spark at all, the coil is definitely faulty. Just be careful with the high voltage—I once nearly got shocked and switched back to using the multimeter. A worn-out ignition coil can cause hard starting or increased fuel consumption. A new one costs around a hundred bucks, half the price of taking it to a repair shop. Sharing this in hopes of saving you some trouble.
