I have an 02 Chevy Trailblazer

I went to start my vehicle up like normal before work. When it was in accessory it was fine but when I tried to turn it over, it all went black. There was no power at all. Couldn't take the key out of accessory. Lights came back on a minute later and I could turn the key. When I tried to start it again, it once again, died. Key locked in ignition. Open the hood and the lights came back on. I tried one more time, Turned over no problem. I did notice, once it was started the battery gauge was rocking between 14 and 17. ( 1/2 way up the gauge and almost 3/4 up the gauge) Lights were flickering whenever I used something electrical ( radio or windows).

Drove it to work just fine turned it off went to test to see if it was gonna glitch, and you guessed it, dead. Wouldn't release the key. Finally lit back up and pulled the key out.

I don't know if it has anything to do with it but today my engine light came on and got a code: P0420 - catalyst system efficiency below threshold. SOMEONE PLEASE HELP!! I just replaced the transmission and really don't want to junk it.


4 Answers 4


First thing to check is the battery terminal connections. It sounds like you could have a bad connection. A high resistance would allow some of the low power circuits to work, but when you try to start it it would fail.

Take the connectors off and clean them.

  • 1
    Exactly this. Seen it happen on many occasions ... sucks every time it happens :o) Commented May 4, 2021 at 18:59

If you're not smelling smoke, it's probably not a short. As a test, pull the leads off the battery terminals, clean the terminals and the clamps, replace the leads, making sure they are tight. Charge your battery. See if this fixes the problem. If not, depending on the battery age, you might need a new battery. A service center can tell you if the battery itself is bad. They would also be able to check your charging system to make sure it's working properly.

  • Why did you delete your previous answer?
    – HandyHowie
    Commented May 6, 2021 at 9:06
  • Somehow when I edited my answer SE kept the old one and created a new one. I deleted the old one.
    – BobT
    Commented May 6, 2021 at 13:36

UPDATE: Changed out the alternator and now it is running like a dime. Thank you all for your answers.

  • Surely this should be marked as the correct answer.
    – HandyHowie
    Commented May 6, 2021 at 9:05
  • It is most likely a coincidence that changing the alternator fixed the problem. A bad alternator does not make the battery go completely dead and then charge back up a minute later. A failing battery or dirty terminals causes this problem. Commented Oct 5, 2021 at 15:55

Its definitely an electrical short issue. maybe a ground not hooked up or something. you said you have the trans replaced recently, see if the shop forgot to plug something in or somethings loose or not grounding properly. the Transmission control module is part of the ignition so that could play a part. assuming this car is automatic.

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