Ok, I keep seeing posts with people struggling with Check engine Lights and asking how to fix them or what other people have done to fix them.

If you own a modded car. like to fix your car yourself, or just want to confirm the repairs done by someone else then you need a scan tool that will show live data.

They are not pricey, you can get them through NAM vendors like ECS Tuning and others.

If you have a ByteTronik tune you can log data with your dongle.

With this data you can see things like:
Misfire (Some tools call it Roughness Monitors)
Fuel System Lean/Rich (See this by watching MAP sensor, O2 readings, and Long/Short Term Fuel Trims)
Catalyst Efficency (See this by watching O2 sensor voltages and the delta between them)
Boost / Vacuum Leaks (See this by watching MAP sensor readings)
Actual Coolant Temp (Do you really trust that dash gauge?)
Air / Fuel Ratio (The factory Primary O2 is decently accurate)
Knock (aka detonation or Pre-ignition)

Most of us have more money invested in our Minis than we would like to admit so protect it by being able to monitor whats going on.

 

Very good post.