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.
Yeah the electrical section is no joke. I work full-time at a dealership and have two kids at home, so I was basically squeezing in 30 minutes of study during lunch and maybe an hour after bedtime if I didn't fall asleep first. What actually helped me was drilling specific diagnostic tree scenarios over and over instead of trying to memorize everything. I also found some free gm approved parts practice material that had realistic question formats, which made the actual exam feel less foreign.
67% is rough but you passed, and that's what counts. I'd go back and focus on the voltage drop and ground circuit questions specifically — those tripped me up too and they show up constantly. It's not about knowing every system cold, it's about trusting the diagnostic process when you're staring at a question that looks like it has two right answers.
Man, I almost quit during my prep when I hit the electrical diagnostic trees. They weren't clicking no matter how many times I went through them and I genuinely thought I was going to fail. What helped me was drilling down into specific systems instead of trying to review everything at once — I spent a solid week on fuel and emissions alone using stuff like gm/questions/fuel systems and emissions 2 and it started to make more sense once I saw the same logic patterns repeat.
67% on electrical is rough but you passed, and that's what counts. Honestly the diagnostic tree questions are just a different kind of thinking than hands-on work and it takes a while to rewire your brain for them. Keep drilling the ones you missed and it'll click.
Congrats on passing! That electrical section is rough — I felt the exact same way when I took it. What actually helped me click with it wasn't drilling the right answers but going back through every question I got wrong and figuring out why the wrong choices were wrong. Like, most of those diagnostic tree questions have two answers that look totally valid, and until you understand what makes one of them fail in a real circuit, you're just guessing. Once I started doing that, the pattern recognition came way faster.
If you want to reinforce that approach on another system, I'd actually suggest working through the gm/questions/fuel systems and emissions 2 section the same way — it's got a lot of that same "eliminate the wrong answer by understanding the failure mode" logic. Didn't think I'd learn much from fuel systems since it wasn't my weak spot, but it sharpened how I think through GM's diagnostic methodology overall. Helps you build the mental model, not just the answer sheet.
Electrical was rough for me too at first. I'm sitting my GM exam in three weeks and I've been grinding practice sets every evening — just hit 74% on my last full mock, which feels like progress but I know I need to push it higher. The diagnostic tree stuff clicked more once I stopped trying to memorize and started actually tracing the logic step by step.
One thing that helped me was doing the gm/questions/fuel systems and emissions 2 questions because it forced me to think about how the systems interact, not just isolated symptoms. If you're still reviewing before your next attempt I'd try that approach — working across systems instead of drilling one area at a time made the electrical reasoning make more sense to me.