July 22nd, 2025 — Issue #0005

Mayday, Mayday, Private CAN Down!!

And The Vehicle Which Would Not Go Over 39 MPH… Sometimes

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Hi Reader,

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Welcome to your weekly boost of inspiration from the shop floor. Torque Authority is not your average industry blog—it's a spark fired from the shop meant to reignite your drive, your grit, and your purpose.

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Each edition delivers a hint of humor and a dose of inspiration drawn from real moments under the hood—lessons on leadership, resilience, and persistence.

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The aim of this newsletter is to help you build a highly skilled, confident, and high-paying automotive future—on your terms. So, join the Torque Authority Hub to find out how!

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If you haven't already heard, Torque Authority Collective is hosting our first LIVE LAB on Tuesday, August 19th at 1:30PM EST!

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Experienced Technicians looking to save time, new technicians wanting to build confidence, and shop owners looking for smarter, faster diagnostics, this is for you!
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Join us in one month for our first LIVE LAB: Diagnose Electrical in 30 minutes or less.
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We're going to cover the essential tips, tricks, and tools to confidently diagnose automotive electrical faults in no time.

From the Driver's Seat—Featured Story

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You road-tested the vehicle like a seasoned pit crew chief—checked every signal, traced every circuit, triple-checked every harness. That CAN system is behaving like a brand-new tool fresh out of the box: clean, confident, and working as it should.

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You even drove the vehicle home overnight to ensure no faults are present. Everything pointed to “no problem found.”

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But then came the bagel stop.

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You roll up to the corner deli on your way to the shop, craving nothing more than a toasted everything bagel with egg and cheese. But as fate would have it, the moment that savory sandwich hit the passenger seat, the dash lit up like a shop floor during electrical diagnostics day. The vehicle lunged into limp mode with all the grace of a rookie tech using a torque wrench for the first time.

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Throttle response? Gone. ETA? Laughable. You find yourself inching toward the shop like a scan tool stuck in a firmware update—slow, uncertain, and painfully aware you've been here before, muttering under your breath and regretting every bite.

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Whatever gremlin had been lurking in the harness, it chose the worst possible moment to make itself known—and that bagel break became the defining clue in a CAN-spiracy you never saw coming.

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The story goes that the EV equivalent of a 'check engine light' was coming on, and the shop brought this vehicle in to start diagnosis.

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Thank goodness, there's at least a code to help!

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So what code is setting? U007C, indicating the private CAN bus between the drive motor and the battery charger module is going offline. The published service information shows that the most likely possible cause is a short in the circuit.

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Okay, no big deal. right? Check the circuits for a short to ground, short together, and short to power.

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But this shop found no faults. This led them to replace the battery charger module. Concern resolved, right? Then while verifying the repair, the vehicle reaches 70 MPH on the freeway and sure enough, there are no issues!

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Until the freeway offramp.

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Just like that, 'Peekaboo!' The malfunction indicator lamp comes back on, and the speed is reduced to 39 MPH.

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With no circuit faults found and the replacement battery charger module not fixing it, that's when I got involved.

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After discussion with the Shop Foreman, it turns out that the light comes on intermittently. However, it has been coming back more frequently as of late.

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To the rescue: Mr. Picoscope! Luckily, this is a quick test. The circuit that needs to be monitored is one of the easiest to access. No trim panels to remove, no bolts to take out. Just straight access to the harness.

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The oscilloscope waveform showed signs of cardiac arrest -- a short to ground flatlining at 0 volts with some random cries for help. So now the fun -- isolating the fault by disconnecting connectors until we have normal waveforms.

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I disconnected a big in-line connector and the communication came right back. Just like the hound dog gaining ground on the prison escapee, we are now on a role!

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Reconnect the in-line connector and... wait a second. It's still working, and the waveform looks good...

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Shoot, I thought to myself. I accidentally fixed it. The fault must be close to this connector then.

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The connector looks good, no chafing nor damage that can be seen. Even the back of the connector is good.

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But wait... that A/C muffler looks shiny.

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Is that harness supposed to be laying on top of that muffler? I mused. I don't think so!

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Sure enough, the harness was worn through where it was sitting on the muffler. My suspicions of a short to ground on the high side of the communication circuits was confirmed. The yellow wire is smooshed and black from corrosion. While pushing that wire onto the muffler I can see my CAN communication go in and out.

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Further investigation showed that previous work had been done on this vehicle. When this harness was moved and re-installed, the routing clips were left loose. The harness should have been pushed down underneath the A/C line and out of the way.

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Since the clips weren't fastened, the harness was left loosely laying on top of the A/C line and created our intermittent issue.

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Turns out, the villain of our electrical saga wasn’t some advanced fault buried in the depths of the system—it was a harness, casually lounging across an A/C line like it was sunbathing at Daytona. The culprit? A few missing routing clips, probably forgotten by someone who thought “close enough” was a viable repair philosophy.

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We re-secured the harness, clasped everything down like a paranoid with trust issues, and watched the limp mode vanish faster than a free donut in the break room.

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The moral of the story? Always double-check your clips, or risk turning someone’s breakfast run into a diagnostic odyssey. Because in your garage, bagels shouldn’t come with a side of CAN failure.

Don't forget we've created a free online Skool community where fellow troubleshooters, thinkers, and diagnostic detectives can swap stories, wisdom, and wiring diagrams. 'Torque Authority' isn't just a newsletter, it's the start of a movement. Come be a founding member by joining the party here:

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Torque Authority Hub is a Skool community/classroom: an all-in-one online space where learning meets connection. Think of it as a hybrid between a private social group and a structured course platform—built for automotive service enthusiasts to share knowledge, spark discussions, and build relationships around our shared interests.

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It’s a place where:

• Courses are organized into modules and lessons, making it easy to learn at your own pace
• Community posts where members ask questions, share wins, or troubleshoot together—like a virtual shop floor
• Gamification (points, levels, rewards) which makes learning feel like leveling up
• Calendars and events where we schedule live trainings, Q&As, or meetups

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We're taking this Torque Authority newsletter and turning it into an interactive pit crew—ready to learn, laugh, and lift each other up. You don't want to miss out on this! Join now—it's free!

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We hope you enjoyed the story! Please share this article with a friend if you did.

In this section each week we highlight a person—an innovator, subscriber, engineer, or even a business—who has made a positive impact in our industry. This is the place in Torque Authority where their authority in the Automotive Industry is highlighted.

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This week's highlight is on Cole Christensen, Cost Per Repair Specialist at Ford Motor Company

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From her early days as a service advisor at a GMC dealership to her current role as a Cost Per Repair Specialist at Ford, Cole has charted a remarkable journey through the industry. Her evolution—from Technical Support Analyst to Field Service Engineer, then on to Cost Per Repair Specialist—reflects not just a mastery of technical detail, but a fierce dedication to continuous growth. She's not only solving problems behind the scenes but also uplifting those around her. She embodies what it means to rise through grit, intelligence, and a commitment to bettering automotive service one vehicle, and one repair, at a time. For the years I've known her, it has been a privilege to know and work with her. Let's hear it for Cole!

One quote of wisdom for you to consider this week...

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This is where we share one practical resource: a tool, app, book, strategy, or event which can have a positive impact in YOUR life.

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This week's Toolbox Tip is on Stack-up Banana-Plug Wires:

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These stack-up Banana-Plug Wires are a MUST HAVE. Want to extend your wire leads while testing? No problem -- these have a stack-up open-end lead on both ends. Want to have an easy loaded voltage drop test? No problem -- just connect these babies to your multimeter, then piggy-back your load off the open stack ports right on the multi-meter! Connection to most DMM's and scopes is also no problem. If you don't already have these in your tool kit, we HIGHLY recommend them!

🔧 Question of the Week What electrical diagnostic tools are your MVPs in the bay? Whether it’s your scan tool that speaks fluent CAN, that humble test light that’s never let you down, or the breakout box that’s bailed you out of a sketchy multiplexed mystery—tell us your favorites!

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📊 Quick Poll Your Diagnosis Spirit Animal. You're staring down a gremlin in the wiring. Which diagnostic move are you most likely to make?

• 🕵️ Multimeter Mastery — Nothing escapes my probes.
• 🪄 Scan Tool Sorcery — I talk to modules like they owe me rent.
• 🔦 Wiggle Test Wizard — If it twitches, I tag it.
• 🥷 Visual Ninja — Spot the chafe, solve the case, no tools required.
• 🍕 Distraction Technique — I grab a snack and hope the fault clears itself.

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✍️ Share Your Story What's the most difficult electrical fault you have located in a harness? We want to hear about your victories—reply with your story and we just might feature it in a future edition!