No start but have power/ Tahoe running and then gages drop

Are you going by the dash ammeter or is that bench testing ? 14.2 voltage is not out of the question even under load. Did you send it to someone you use @ work or shop specific for Alternator ? I must agree, don't open your wallet to the Dealership, they'll empty it for you. You got too much advise all to no results. When you said it would not start, I would be looking at Battery/Alternator, you mentioned you have already replaced the cables, what's left ? JMHO
David g.

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RED TAHOE LS said:

Are you going by the dash ammeter or is that bench testing ? 14.2 voltage is not out of the question even under load. Did you send it to someone you use @ work or shop specific for Alternator ? I must agree, don't open your wallet to the Dealership, they'll empty it for you. You got too much advise all to no results. When you said it would not start, I would be looking at Battery/Alternator, you mentioned you have already replaced the cables, what's left ? JMHO
David g.

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No I talked to my boss and he told to to use that battery charger and have the Tahoe running and then hold the load button and it would go to 12, the battery alone I pulled it out about a week ago and tested it the same way and it was good I even put a different battery from a 08 GMC Sierra and it worked fine for a day and had the same issue, I want to take the alternator off completely and test it at the parts store we do a lot of business with, well the only thing that left is to replace the whole car lol, I haven’t had a issue in two days and today around noon it just acted like there was no power all the light and gages came on but would not start.. I’m at wits ends with it


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I rest my case. Two different batteries, Alternator will not keep either one charged Parts store people are a dime a dozen, probably offended some, so be it. Good luck.
David g.

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RED TAHOE LS said:

I rest my case. Two different batteries, Alternator will not keep either one charged Parts store people are a dime a dozen, probably offended some, so be it. Good luck.
David g.

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Well the battery stays charged, I’m looking at wire diagrams from service bulletins I found #08-07-30-021H is a new one I found, I’m gonna do more looking at wire harness, In that bulletin they give you locations one where to check and before I waste time at the store I’m gonna take a alternator off the other truck and see if that changes anything, I’m waiting for it to not start again so I can get under it and hit the starter to see if it thinks it bad


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TaboltB2015 said:

Well the battery stays charged, I’m looking at wire diagrams from service bulletins I found #08-07-30-021H is a new one I found, I’m gonna do more looking at wire harness, In that bulletin they give you locations one where to check and before I waste time at the store I’m gonna take a alternator off the other truck and see if that changes anything, I’m waiting for it to not start again so I can get under it and hit the starter to see if it thinks it bad


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I just jump started a car and everything in side of the Tahoe was dead gages were 0” rear lift didn’t wanna close, tomorrow definitely taking alternator off and try another one


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Did you test those pins I asked you about earlier? You can test them right on the obd port under the dash with a multimeter. It should take you less than three seconds to get a reading on those pins. Do it when it didn't want to start

about20ninj45 said:

Did you test those pins I asked you about earlier? You can test them right on the obd port under the dash with a multimeter. It should take you less than three seconds to get a reading on those pins. Do it when it didn't want to start

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I haven’t yet today just wasn’t a day to be outside. I’ll have to see if I can find the multimeter and just keep it in the Tahoe along with the scanner. I was able to start it and bring it around to the front of the office at work and I scanned the engine light and I got u0073 can bus off, I’ll definitely need to test that and the alternator as well that was I can just start crossing stuff of the list to check..


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What year is this Tahoe ? And what got it in this predicament, accident, recently purchased, don't know the background, I'm curious, trying to keep you from going nuts, a car can do that to you. [emoji3]
David g.

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Did you ever get the battery post shims and tighten up the cables???

TaboltB2015 said:

...scanned the engine light and I got u0073 can bus off

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U2100 is for CAN Bus. U0073 is one of three, U0073 00 - Control Module Communication Bus Off, U0073 71 ECU HS Bus Off, U0073 72 ECU LS Bus Off

The book says:

2. This DTC cannot be retrieved with a current status. Diagnosis is accomplished using the symptom Scan
Tool Does Not Communicate with High Speed GMLAN Device or Scan Tool Does Not
Communicate with Low Speed GMLAN Device.

I'm not well enough to look that up right now.