July 1st, 2025 — Issue #0002

No-Crank Nonsense: A Hidden Connector's Dirty Little Secret

How One Dangling Plug in the Rear Bumper Shut Down an Equinox

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Hi Reader,

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Welcome to your weekly boost of inspiration from the shop floor!

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Torque Authority is a compilation of hard-earned life lessons on leadership, resilience, and persistence from my experiences in the automotive industry. It comes delivered with a hint of humor and a dose of inspiration drawn from the frontlines of automotive service.

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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.

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Ready to unlock the potential within you and become a more confident automotive diagnostician? Check out my book Hotwire Your Skills: The 10-Step Playbook to Six-Figure Success for Automotive Technicians.

Torque Authority subscribers get an exclusive discount here!

You hop into the driver's seat, step on the brake, and push the Start button.

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Nothing. No start.

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Worse yet, you hold down the Start button for 5 seconds to try to engage 'Service Mode' (Key ON, Engine OFF) and the vehicle powers up...

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...but then 2 seconds later shuts itself down.

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You can't get any DTC's because the vehicle won't stay keyed-on long enough for the scan tool to connect.

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The only additional clues you have include a DTC for a Power Mode Switch Circuit mismatch and a few other codes for Low Speed GMLAN network communication issues (which the vehicle had previously broadcasted to the connected vehicle database).

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The shop had already tried a new start/stop button, two new key fobs, and a few different modules.

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I travelled to assist this shop and after a few weeks of various testing procedures and digging, we thought we had it—the Body Control Module connectors were all closely inspected and, after they were all reconnected, the concern went away.

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It must have been a poor connection.

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Or so I thought...

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A full week of driving and testing went by with no faults. Naturally, the vehicle wanted to wait until it had an audience, because it decided to act up the moment the customer came back to pick it up.

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Like some twisted automotive peekaboo. We were ready to call it fixed, but fate—and faulty wiring—had other plans.

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This is when I took a step back to re-evaluate.

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I reviewed the initial clues the vehicle gave us—especially the clue regarding the Low Speed GMLAN DTCs.

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Admittedly, I had subconsciously written off those DTCs as something irrelevant. Probably just a result of the battery dying or something, I must have thought.

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Unsure of what to do next, I studied the Low Speed GMLAN wiring schematic for any clues.

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And BAM—there it was!

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The schematic showed how the BCM and KECM are a young married couple, which, at startup are supposed to be whispering sweet nothings to each other across the GMLAN.

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What if this power mode mismatch is because two modules aren't able to talk with each other right after startup? I thought to myself.

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Intrigued, I connected the oscilloscope to the Low Speed GMLAN. With the key turned on (for that two second window), this is what I saw:

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Rather than whispering sweet nothings, these two modules were communicating like a hard-of-hearing old married couple—lots of shouting, no actual understanding.

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On the same wiring schematic, I looked for any test points. Somewhere I could isolate part of the GMLAN circuit and re-test.
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The first one my eyes were drawn to was connector X400 which, according to the service information, was located in the right rear of the bumper.

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And that's where I found it: dipped in guacamole and left out to rot since the Super Bowl.

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Curious, I decided to leave this bumper harness connector X400 unplugged, then again monitor the Low Speed GMLAN.

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That old couple (the BCM and KECM) had their hearing restored and their love reignited. The vehicle keyed on normally and started up without issue!

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So, what caused all of this? A little bit of detective work found the root cause:

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Laying loosely inside the bumper was a mounting bracket for this connector X400. Rather than being popped into its mounting studs where it was supposed to be, the connector X400 was simply dangling down below, where road spray was able to get it wet.

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The bracket was supposed to be mounted here (image above), to keep the X400 connector up and out of the way of excess moisture.

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A closer look at the rear bumper and I could tell—body work had been done at one point (bumper paint was just slightly off from the rest of the vehicle paint)—so it appears that the body repair center neglected to re-install the bracket for X400.

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A few key valuable lessons I learned from this case:

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1. Put things back where they were—the little things, like where a harness or connector is supposed to be mounted—really do matter!
2. When you're stuck, go back to the basics. Don't rule out the little clues which seem unrelated as they may point you in the right direction.
3. If you didn't find a clear failure and the concern goes away, you likely didn't fix it—instead, you scared the fault into hiding.

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

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Join Torque Authority Hub: Where Automotive Technicians Transform into Diagnostic Daredevils. Embrace your worth, master your craft, and drive towards financial autonomy with a community that gets it.

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

Behind the Wrench: Why Freedom Matters

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Our industry thrives because each of us has the liberty to innovate, specialize, and serve.

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This Independence Day, let’s celebrate our freedom to choose our own career paths and the blessing of owning a skillset that is always in demand, granting us the freedom to work and live life where and how we want.

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Enjoy the sparks in the sky and the freedom in your garage. Happy Independence Day!

In this section I will share one quote of wisdom for you to consider this week...

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This is where I share one practical resource: a tool, app, book, strategy, or event which has had a positive impact in my life.

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This week's Toolbox Tip is on one of my favorite tools: The Oscilloscope!

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The more time I spend experimenting with or troubleshooting with my Picoscope, the more I find how valuable it truly is. This black box shouldn't be ominous or scary -- open it up and try experimenting with it if you have access to one but don't have much experience with it.

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An oscilloscope lets you see real-time electrical waveforms—showing the exact voltage, timing, and patterns that drive sensors and actuators. Unlike a scan tool’s static data snapshot, or a multimeter's narrow capture window, a scope captures intermittent glitches and fast transients as they happen. That clarity means you spend less time guessing and more time pinpointing the root cause. By visualizing signals down to the microsecond, you can confirm whether an injector pulse is good, a crank sensor output is clean, or if there is something dumping noise onto the communication network. With that level of insight, you slash diagnostic time, avoid unnecessary parts swaps, and gain confidence that your repair truly fixed the issue.

🔧 Question of the Week If you had absolute freedom to build your ultimate diagnostic setup—no budget, no space constraints—what one feature or tool would you add first, and how would it give you the greatest independence on the job? Let me know by responding to this email or by sending me a DM on LinkedIn!

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📊 Quick Poll What is your biggest diagnostic time-sink?

• Hunting down intermittent gremlins
• Waiting on parts delivery
• Digging through OEM service info
• Explaining findings in your write-up (or to the customer)

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✍️ Share Your Story What are some of your shop's July 4th traditions? Send me an email letting me know and you could be featured in one of the next editions!