Solved: Detecting a Jeep Grand Cherokee's Communication Faults
A 2015 Jeep Grand Cherokee 3.6L suffered from communication network faults that would leave the electronically shifted transmission in 'PARK.'
Get caught up with all the details on this vehicle diagnostic case.
Given this information, what would you do next?
- Replace the least expensive node first (TCM or ESM)
- Replace both the ESM and TCM
- Isolate nodes individually and recapture CAN waveforms
- Isolate nodes individually and re-scan for DTCs
For those of you who chose answer No. 3, congratulations! The combination of the DTCs stored and the topology isolated the fault to one of only two nodes. Isolation of the most accessible node was carried out and the anomaly was eliminated from the CAN waveforms, leading to proper communication, and without DTCs.
Answer No. 1 is incorrect as it is rarely prudent practice to replace parts simply due to the cost. Replacing the nodes arbitrarily is not prudent, especially considering there are other tests to be carried out.
Answer No. 2 is incorrect as there is only one faulty node present and considering the cost as well, this would set the customer back financially for no good reason.
Answer No. 4 holds merit but the true data reflecting the symptom is the skewed CAN bus waveforms. The DTCs are simply a result of the corrupted bus. The more valuable reflection of a correct repair (or bypassing of the fault) is to monitor for healthy CAN bus waveforms.
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.