GM certified technician exam — passed but the electrical section nearly broke me
Got my GM certification results last Tuesday. Passed overall but my electrical systems score was 67%, which is way too close for comfort. The rest of the exam I felt solid on — somewhere around 80–85% on engine performance and transmission diagnosis. But the electrical diagnostic tree questions were something else entirely.
I've been a GM tech for 11 years and I thought I knew electrical. Turns out there's a real difference between knowing how to fix a car and knowing how to answer a multiple choice question about the process. The questions are super specific about GM diagnostic procedures — if you do it in a slightly different order in practice, those answers will trip you up every time.
If you're prepping, get into the GM Service Information portal and read the diagnostic procedures word for word. Don't rely on your shop experience alone. I spent 4 weeks studying, maybe 1.5 hours a night, and I should've spent 3 of those weeks on just electrical and CAN bus topics.
Anyone else find the hybrid and EV content showing up more heavily now? I had at least 12–15 questions that touched on high-voltage systems and I wasn't prepared for that volume at all.
The EV and hybrid content has definitely grown. I took it two years ago and maybe had 5 or 6 questions on high-voltage. Sounds like they've been adding more as GM pushes toward electrification. Good heads up for people prepping right now.
Congrats on passing! The diagnostic procedure order thing is exactly right. I failed the first time partly because I was answering from muscle memory of what I do in the bay, not what the SI says to do.
Second attempt I memorized the step sequences from SI and jumped from 71% to 84% on electrical. The content didn't change, just how I framed my answers.
11 years in and still had to study hard for it — that says something about how the exam is structured. It's testing GM protocol knowledge, not experience. Important distinction for new techs to understand going in.
The CAN bus questions specifically require you to know the topology and fault isolation logic cold. That's not something you can wing from shop instinct. Flashcards on the network architecture helped me more than anything else.
Honestly I almost walked away from the GM cert twice. The electrical diagnostic tree questions felt like they were written in another language, and I kept second guessing every answer. Sounds like you had the exact same experience I did, 67% is too close but a pass is a pass and don't let anyone tell you different. What turned it around for me was drilling the diagnostic flow over and over until the logic actually clicked instead of just memorizing. I leaned hard on practice questions, including a bunch of free gm approved parts ones that helped way more than I expected.
The thing nobody tells you is that the electrical section punishes guessing. You have to follow the tree exactly the way GM wants, not the way that makes sense in your head. I wasn't sure I'd ever get it. But it does sink in eventually if you keep grinding. Congrats on passing, you earned it, and trust me that score line fades the second you've got the cert in hand.