Why is my 2021 Chevy Trailblazer check engine light on?

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May 12, 2025 at 5:10 pm #1152 Reply
Amanda
I’m posting for my friend who is having a car problem, maybe y’all could figure out the problem.

She has a 2021 Chevy Trailblazer: Check engine light came on, parts store put machine on it, said throttle body needs cleaned. Took to mechanic, he cleaned throttle body, check engine light still on. His machine mentioned o2 sensors and mass air flow, but he said all of that was good.

He cleared the codes, but as soon as you start the car, the check engine light comes right back in.
May 12, 2025 at 5:10 pm #1153 Reply
Collin
Take it to another shop where they can diagnose the issue & hopefully give you a better outcome. Some mechanics make mistakes, so it’s always better to get a second opinion from someone else with a scanner and knowledge to diagnose the issue.
May 12, 2025 at 5:11 pm #1154 Reply
Sean
A DTC would help. Also, it’s a ‘21, it should go to the dealer.
May 12, 2025 at 5:11 pm #1155 Reply
Kevin
Geez. Hey while anyone out there is reading this… working on a car… it’s blue, 4 doors…. Makes a noise… what do you think it is? A guy said I was crazy, and he doesn’t hear no noise, so I think he’s trying to rip me off… asking for a friend. TIA.
May 12, 2025 at 5:11 pm #1156 Reply
Joseph
You said they cleaned the throttle body.
1. Was it done properly and with the correct product?
2. Was a throttle relearn conducted once the body was cleaned and the code cleared?
May 12, 2025 at 5:12 pm #1157 Reply
Mark
Clearing codes does not fix the car. Codes are not a diagnosis. Stop trying to save money by spending money. Get this to someone who actually knows how to fix cars.
May 12, 2025 at 5:12 pm #1158 Reply
Tony
There are 2 codes that normally throw on these, I can only remember one, p1101, if it’s that it needs a new valve cover, if it’s the other for mass airflow, there’s a bulletin for the pigtail going to the sensor breaking internally, needs to be rewired.

But get the code first.
May 12, 2025 at 5:13 pm #1159 Reply
Besticanafford
I once had a kid scan my car while I was away from my machine. CEL came on while I was out of town. He told me my EVAP code was and HVAC code. Then explained to me how there must be a problem with my AC.

Thankfully, I was looking over his shoulder.

Don’t trust those kids to fix your car.
May 12, 2025 at 5:13 pm #1160 Reply
Jimmy
Try running marvel mystery oil through the tank two times. That cleared my 02 codes.
May 12, 2025 at 5:13 pm #1161 Reply
Lance
A new scan is required to nail the problem down better! Check the live data and see what is happening!
May 12, 2025 at 5:13 pm #1162 Reply
Franken
No symptom or even codes. How is anyone gonna help you on here because we don’t care what someone else said.
May 12, 2025 at 5:13 pm #1163 Reply
John
2021 unless using some really poor quality gas doubtful cleaning it would be any help , should not be dirty enough to matter. Unless abused high milage vehicle.
May 12, 2025 at 5:14 pm #1164 Reply
Clifford
Yeah, you need to use this tool called a fogger it will help you to find your vacuum leak if you’re not careful you could even throw the thing into safe mode all over a vacuum leak that’s one thing about the new Chevy things you get a vacuum light vacuum leak or problem with your EGR etc etc you can throw the thing into safe mode you could try a hard reset disconnect both battery cables for about 30 minutes and then make sure you put the positive on first and then apply the negative.
May 12, 2025 at 5:14 pm #1165 Reply
Amanda
Find a different mechanic, clearing the codes does not fix problems, it just clears the readiness monitors which reset after a pre-determined amount of time / starts / running conditions. If there were no problems, the codes would have cleared themselves.
May 12, 2025 at 5:14 pm #1166 Reply
Abraham
PSA: Parts stores don’t diagnose codes. They read them out to you. Stop going to auto zone for diagnostics.
May 12, 2025 at 5:15 pm #1167 Reply
Mike
Sounds like you have a problem. You can do more harm than good by throwing parts store crap at a problem with ZERO understanding of what the problem actually is. Find a good diagnostic tech in your area and spend the couple of hundred for an actual diagnosis. Just for powertrain alone in 21 there are THOUSANDS of DTC if you count generic and manufacturer specific.
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Why is my 2021 Chevy Trailblazer check engine light on?

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