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Voltage drop when I turn the key or lights on

I have a 2003 Chevy Tahoe. I recently changed the starter in it and everything worked fine for one day. It was starting better than it had ever been and I started it four or five times then went to town. All was great. This morning when I went out to get in it I turned the key and the only thing that would happen is that the check engine light came on. It acted like an electrical problem the other lights flickered on but then went off. I did the obvious and took the starter back off and checked all the wires and put it back on still the same thing. I got my meter out and at the battery it showed 12.65 volts but then I turn the key on and it dropped to 5.46 volts. it does the same thing when I try to put the headlights on. I've checked every fuse I know and checked all the grounds, cleaned them up. Also, the Dinger does not go off when I turn the lights on or put the key in the ignition either. I've chased wires all day and I'm at my end. Can it be the ignition switch.

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@cklynch @oldturkey03 sounds right here but to check for certain us a load tester on the battery by itself not connected to the car . If you get the same results then its the battery but if the battery holds true then hook it back up to the car and test it again . If it dies off I have seen a short in the ECM cause this kind of drop

Hope this helps

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Thank you for your response. It was the battery

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@cklynch "12.65 volts but then I turn the key on and it dropped to 5.46 volts" indicative of a bad battery. You have some shorted cells. Replacing the battery will fix this.

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Thank you thank you. It was the battery. I assumed that because it was holding a good charge it was good. Learned something new today.

I'm sorry for the delayed response but I haven't had time to mess with it until now. Had to catch up on the lost day of work.

Again....thank you very much

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I got the same issue gents, but I tried my car battery to another vehicle and to my surprise it gave power for 1 click start

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Was it the same make and model car?

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I tried to clean the starter, igniter, distributor change spark plug all fuse check and relays, I'm I missing something?

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Chris Lynch will be eternally grateful.
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