Solved: A Toyota Land Cruiser's power problem

May 9, 2024

A technician was facing a strange issue with a 2015 Toyota Land Cruiser with a 5.7L V8 engine. It was experiencing what he described as a strange loss of power output. Motor Age Technical Editor Brandon Steckler jumped in to help with the diagnosis.

Brandon Steckler

This damage to the fuel tank pressure sensor 5v reference wire occurred because the wire melted as it encountered the exhaust system. As the 5v reference wire found a path to ground, it pulled the signal low and created the elusive driveability symptom.

A technician was facing a strange issue with a 2015 Toyota Land Cruiser with a 5.7L V8 engine. It was experiencing what he described as a strange loss of power output. Motor Age Technical Editor Brandon Steckler jumped in to help with the diagnosis.

Steckler thought it was a straight-forward issue, but was faced with helping the young tech obtain the needed data. You can get reacquiainted with the Toyota case's details here.

Here are the four options Steckler offered. Which did you choose?

Replace PCM for erratic internally shorted 5V reference
Monitor 5V reference circuit at PCM, with amp probe
Rewire all the 5V reference circuit feeds on the vehicle
Replace CKP/CMP sensors for intermittent 5V ref short to ground

For those of you who chose answer No. 2, congratulations. An amp probe place around the 5V reference wire of the PCM would’ve shown an increase in current each time the sensor signals failed.

Careful inspection prior to more pinpointed testing of the wire harness would’ve revealed a poorly secured harness. The connector pigtail for the fuel tank pressure sensor allowed the 5v reference wire to melt on the exhaust pipe and short the signal to ground, pulling it low and causing the stall (See the image).

Although a faulty PCM could cause this issue, it wouldn’t be wise to condemn a computer without eliminating external faults. Rewiring all existing 5V reference circuits would’ve solved the issue but would be a tremendous investment in time and not an efficient use of that time. Replacing the CMP/CKP sensors is not going to solve this issue but could be the cause of the stalling symptom. Without evidence to support the sensor failure, it would simply be a guess and not very professional to conduct analyses like that.

Motor Age Technical Editor Brandon Steckler presents a new case for the Data Doesn't Lie each month.

About the Author

Brandon Steckler | Motor Age Technical Editor

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.