2003 Chevy Avalanche Z66 5.3

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My Mother-in-Law has a 2003 Chevy Avalanche with the 5.3 with over 200,000 miles which has been very well maintained but today she started having problems which seem to be electrical. She just put a new battery in so I think that is a eliminated problem however, when your driving its fine, but when you let off the gas pedal the vehicle wants to start shutting down and gauges start acting weird. I thought problems with the alternator but seems more like a vacuum problem or possibly the main computer. Any thoughts?
 
Disassemble and clean the battery, alternator, and ground connections. Also, have the charging system tested (many parts stores do this free).
 
Will do so am I assuming its the alternator? Correct me if I am thinking wrong. I have disassembled those things just havent had time to run a test on them. I am just trying to look into it before driving because it shuts off when you release the gas. The battery is new, only a week old.
 
When you say she just put in a new battery, are you talking like within the last month or two, or do you mean like within the past day or two?

First thing I would do is check the connections on the battery. Make sure everything is clean and was installed correctly.

Also, check out the problem for yourself. Some people speak in hyperbole and all the problems described are really just that the engine idled so low it almost choked itself out. Which is something that can happen after a battery has been disconnected, as the ECU is relearning the engine and where to idle it as low as possible without choking the engine.
 
Hello,
What does TBS mean? Is it TPS (Throttle Positioning Sensor?)
MAF I got. Mass Air Flow sensor.
What does CTS mean? Is it CPS (Cam or Crankshaft Positioning Sensor?) Kira
 
Possible Idle Air Control Valve? That will make cars stumble and sometimes die off throttle. Fairly common on high mileage GM stuff.
 
The side post terminals on that truck have three common problems. First is that people tend to under tighten them, leading to a loose connection and flaky problems. Second- many times there is corrosion build up from the previous battery, which of course can cause issues. Lastly is stripped out bolts from too many installations and/or improper tightening. I recommend replacing them with the battery.

Naturally there can be a combination of these three things too. Seen it before many times. Check them first.
 
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