Chevy Suburban Electrical Power Management

2010 Chevy Suburban 1500 4wd. Had system Checked at dealer. Started truck and let run to warm up, as I walked out to drive I smelled an electrical burning smell. I got in the truck and checked the basics and all seemed fine. As I was driving the Volt gauge was showing under 14 volts. As I drove it dropped even lower almost to what I figure was not much more than 12v.

When I shut off the truck I waited short time and then re-started voltage back up to over 14v. I figured that it was the battery just recovering. Drove my Chevy again and the voltage dropped as before. Sent to service at dealership then checked and stated that the charging system was working as designed. Does that sound right to you?

Question:
Does the system operate as he told me? Why would it allow the voltage to drop down to almost 12v while running? Took vehicle to my son's repair shop and tested voltage it was at 12.9 when I first got there and then went to 13.7 before dropping back to 12.5 a short time later.Tech told me that the computer shuts the charging down when the vehicle doesn't need it. Sounds like a story to me, and why the electrical burning smell, something def cooked under the hood.

Answer:
Yes, the GM Tech was correct. This charging system is called "Electrical Power Management (EPM)". Basically a sensor on the positive battery cable senses battery voltage / amperage and electrical load while the truck is running. Then the Body Control Module(BCM) determines how much alternator charging capacity is needed. The BCM tells the Powertrain Computer (PCM) how much charging is needed, then the PCM controls the voltage regulator as a pulsed width signal for a controlled output.

For example, when there is a heavy electrical load such as the rear defroster, blower on high speed, headlights on, engine at idle- the PCM will boost the charging voltage. This system is designed to extend battery and alternator life.

Now, the burning smell does not seem related. If the truck is absolutely new with very low miles, then some smells are normal. If something has melted, I would assume the Tech would have spotted that quite quickly. Maybe there is just some plastic melted on the exhaust. Burned wires under the hood would have been easily seen and repaired.

Question:
What would cause my older GMC Suburban truck to stall while sitting still in gear, and only when outside temperature is above 50 degrees?

Answer:
A lot of possibilities there that can cause that problem. If the timing was set correctly, and that includes unplugging the ESC connector while doing the procedure, then that shouldn't be an issue. A bad coil, or even spark plugs and wires can do this at times.

You could even have a cam that is going flat if you have a lot of miles on the truck or have driven it hard over the years.

If you have a carb, I'm sure it probably needs a good cleaning/rebuild/adjustment. A throttle body can gum up too and injectors can go bad over the years. Quite a few things to check that can all cause driveability issues.

Question
2004 Chevy Suburban 5.3 v8 starts and immediately stalls. When given gas doesn't even turn over. Radio wont work but all dash lights work. Diagnostic tool wont read anything. But truck reads unknown driver. Tried disconnecting battery did nothing. Please help.

ANSWER

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