A client of mine was faced with a 2008 Jeep Wrangler with a 3.8L engine. For unknown reasons, the engine was previously replaced with three different units, and at least one replacement PCM.
Given this information, what would you do next?
- Fix the wiring first and re-examine
- Replace the CMP sensor and re-examine
- Condemn the CMP reluctor for improper configuration
- Inspect the CMP reluctor with a borescope
For those of you who chose answer No. 1, congratulations! The shoddy wiring repair is something to correct before continuing further. Even a positive test result at the time of testing may be an intermittent loss of continuity under other operating conditions.
Answer No. 2 is not correct. Although a faulty CMP sensor could cause the symptom, we would need further evidence to responsibly condemn. Further testing would be required, and with the poor circuit conditions already discovered, it would not be a recommended path to travel.
Answers No. 3 and No. 4 are logical answers. As I noticed that the captured correlation waveform from this vehicle was certainly suspect, examining the CMP reluctor would not be an illogical thought, especially since the faulted pattern seemed to repeat. There was an excellent chance that this remanufactured engine was either assembled with the wrong CMP reluctor or the reluctor had damaged/bent teeth. We chose to repair the wiring first and then re-evaluate. The chosen path paid off. Repairing the wiring left the vehicle fault-free (Figure 1).
Be sure to read the next Motor Age issue for the answer to this month’s challenge and what was discovered!
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.