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    The Trainer #152: Crankshaft Variation Relearn Procedure

    Sept. 17, 2024
    For decades, technicians have made it procedural for a PCM to relearn an engine’s crankshaft rotational speed variation. They typically carry out this procedure with initiation from a scan tool upon completing many engine mechanical repairs or engine component replacements. Many techs are all too familiar with the repercussions if this procedure is not carried out, but honestly, many still don’t know why.

    Motor Age Technical Editor, Brandon Steckler is back again for another episode of The Trainer. In this episode, Brandon discusses what the PCM sees and monitors to determine if a misfire is present. Mandated by OBDII regulations, the PCM must accurately detect misfires to stay emissions-compliant. As the crankshaft rotates cycle per cycle every component of that rotating unit vibrates and has minor imbalances that are unique to it, much like a fingerprint. From the assembly line, the PCM is allowed to become familiar with these minor imbalances (or rotational speed variations) so that it will know what “normal’ looks like. But as the vehicle ages and components wear and require replacement, a new characteristic of rotational speed variations are present and have not yet been properly introduced.

    Without the PCM knowing of these new characteristics it will mistakenly identify them as single-cylinder and/or multiple-cylinder misfires. This includes components associated with the rotating piston and rod assembly as well as the components responsible for rotational speed detection (like the PCM and the CKP sensors).

    Stick with Brandon as he demonstrates how these minor variations appear as imbalances to the PCM and how important it is to properly introduce them to the PCM via the Crankshaft Speed Variation Relearn Procedure to avoid mistakenly identified misfires and driveability concerns, all in this episode of The Trainer. 

    About the Author

    Brandon Steckler | Technical Editor | Motor Age

    Brandon began his career in Northampton County Community College in Bethlehem, Pennsylvania, where he was a student of GM’s Automotive Service Educational program. In 2001, he graduated top of his class and earned the GM Leadership award for his efforts. He later began working as a technician at a Saturn dealership in Reading, Pennsylvania, where he quickly attained Master Technician status. He later transitioned to working with Hondas, where he aggressively worked to attain another Master Technician status.

    Always having a passion for a full understanding of system/component functionality, he rapidly earned a reputation for deciphering strange failures at an efficient pace and became known as an information specialist among the staff and peers at the dealership. In search of new challenges, he transitioned away from the dealership and to the independent world, where he specialized in diagnostics and driveability. 

    Today, he is an instructor with both Carquest Technical Institute and Worldpac Training Institute. Along with beta testing for Automotive Test Solutions, he develops curriculum/submits case studies for educational purposes. Through Steckler Automotive Technical Services, LLC., Brandon also provides telephone and live technical support, as well as private training, for technicians all across the world.

    Brandon holds ASE certifications A1-A9 as well as C1 (Service Consultant). He is certified as an Advanced Level Specialist in L1 (Advanced Engine Performance), L2 (Advanced Diesel Engine Performance), L3 (Hybrid/EV Specialist), L4 (ADAS) and xEV-Level 2 (Technician electrical safety).

    He contributes weekly to Facebook automotive chat groups, has authored several books and classes, and truly enjoys traveling across the globe to help other technicians attain a level of understanding that will serve them well throughout their careers.  

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