What's going on guys, this is Frankie with DIYAutoTune and AMP EFI. Today we’re going to go over another basic tech video. We’ll cover tooth loggers—what they are, why we need them, how to record them, and how to read them at a basic level.
Everything referenced here comes from the in-depth article on the DIYAutoTune website called “Using the Tooth Logger and Composite Logger” That guide goes much deeper, showing how to diagnose issues, as well as signal examples in case there’s a choppy signal. This write-up is intended as a simple introduction, while the full article provides the advanced details.
Getting Set Up
Here, the sample MS3X is connected to a JimStim for power and is linked to TunerStudio on the laptop.
Open up TunerStudio and go to the gauge cluster view, as if you were sitting in your car with the ECU connected and powered up.
Navigating to the Logger
At the top left of TunerStudio, select the tab labeled “Diagnostics and High Speed Loggers.”
Once there, look to the left for the “Logger Type” dropdown menu and select “Tooth Logger.”
Before starting, make sure to check the box labeled “Capture to log file.” This ensures the data will be saved. If you don’t click this box before starting, you won’t be able to save the file when the session ends.
Reading a Tooth Log
What you’ll see looks like a bar chart. Each bar represents one tooth on the trigger wheel, and the height represents the time it takes for the ECU to read from one tooth to the next.
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Rising Edge: Measures the time from the leading edge of one tooth to the leading edge of the next.
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Falling Edge: Measures the time from the trailing edge of one tooth to the trailing edge of the next.
On a 36-1 trigger wheel, you’ll notice one tall bar that’s about double the others. This represents the missing tooth.
Saving and Clearing Logs
Once you’ve recorded enough data, press “Stop.” The file will save automatically if you had “Capture to log file” checked. You can then clear the logger and return to the gauge cluster.
Why Tooth Logs Are Important
The tooth logger is a crucial troubleshooting tool whenever you run into crank signal issues. Our support team frequently requests tooth logs (along with your tune file and standard data logs) to help diagnose problems. These files let us see exactly what the ECU is reading from the crank sensor.
Understanding and capturing tooth logs properly will make troubleshooting faster and more accurate.