If you are investigating rough running after spark-plug replacement, save every stored and pending code before clearing anything. Save misfire codes and cylinder counters before clearing them. Record the engine temperature and load alongside the reading; the same value can mean different things in different conditions.
A basic reader may not access every module. Recheck the correct plug type, connector seating, and any parts moved during the job. Use the exact vehicle’s service information to interpret the result.
Quick educational note
For information, not a diagnosis or repair instruction. Vehicle-specific checks are still required. Consult the manufacturer's guidance and a qualified technician.
How to use this information
This article explains general principles and does not establish what is wrong with your vehicle. Read the content limitations.