2000 Chevy Tahoe 5.3 V8. new alternator, new battery still won't start. Help is appreciated.

[2000Tahoe53V8]

Ok, so this stated last Friday night when I started the tahoe. I was still in my drive way when it sputtered and died. Had it on for about 5 min. I started by putting a code reader; 4 codes popped up:

1) U1026 - Loss of class 2 communication with ATC
2) P1637 - Generator L - Terminal Circuit
3) P0463 - Fuel Level Sensor Circuit High Voltage
4) P0108 - Manifold Ablsolute Pressure (MAP) Sensor Circuit High Voltage

I bought the Tahoe used with dash light issues and fuel pump readings not being accurate. This was all I knew from when I purchased it in July 21. I saw the P1637 so I assumed it was the alternator. Volt meter read that the battery was at 12.16. So I puchased a new alternator, installed it and still no start. I was not sure if this Tahoe came with a alternator fuse line. Traced the wire from alternator to battery, could not find one. So I ruled that out. Then I went ahead a purchased new battery, installed it and still no start. It cranks though.

A little help from you guys would be appreciated.

Thanks

 

[MassHoe04]

You may have some bad grounds. Check them to be sure they are ALL clean and tight.

You may have corroded pins and connectors on the PCM.

There are some dead links in the article, but may be some clues in this write-up that may lead you to check out what connections look like at the PCM...

DTC P1637 Generator L-Terminal Circuit

Here is another write-up, that mentions high voltage on the MAP sensor circuit...
That to kind of leads me to believe that there is something with poor electrical connections at the PCM and/or ECM.

https://www.carparts.com/blog/p0108-code-manifold-absolute-pressurebarometric-pressure-high/

That is where I would probably start. Grounds and connections at/in the PCM.

Good luck! Keep us posted.

 

[2000Tahoe53V8]

Thank you! @MassHoe04

It turned out the be the fuel pump. Last thing I'd checked.

 

[OR VietVet]

Not so sure all 4 codes are related to fuel pump. Are you saying that before this no start problem, you had no CEL? A code(s) may still come back. Did you do the fuel filter when you did the fuel pump?

https://www.rockauto.com/en/moreinfo.php?pk=360047&cc=1361551&pt=6200&jsn=1269

 

[Russ]

None of those codes were related to the fact that the engine didn't start. When an engine cranks but does not start there are 2 questions to first answer- "does it have good spark?" & "does it have the proper fuel pressure?".

Pulling codes will almost never lead one in the right direction on a no-start, the basics need to be checked first. An engine will start and run with tons of codes that are irrelevant.

 

[rockola1971]

None of those codes were related to the fact that the engine didn't start. When an engine cranks but does not start there are 2 questions to first answer- "does it have good spark?" & "does it have the proper fuel pressure?".

Pulling codes will almost never lead one in the right direction on a no-start, the basics need to be checked first. An engine will start and run with tons of codes that are irrelevant.

You forgot Air! Suck, Squeeze, Bang, Blow. 4cyle ICE and also the Brayton Cycle.