11 Yukon XL Denali Electrical Issue P0621 SOLVED

[SteelBaller3]

 

[SteelBaller3]

 

[SteelBaller3]

 

[SteelBaller3]

 

[SteelBaller3]

 

[SteelBaller3]

 

[SteelBaller3]

Again, no check engine light. Also scanner says module not supported when trying to do component testing so it seems like ecm to me but idk anything about this stuff.

 

[SteelBaller3]

Sorry for the frustration with me running tests and responses, I have a 1 and 3 year old and work 12 hrs a day and also not an electrician. Just trying things suggested and hoping someone can point me in the right direction.

 

[SpareParts]

All of them look like history codes to me.
KOEO clear all codes. Then look again, i bet they all will still be there. It just takes time for them to disappear.
I will usually get codes like that if the battery is too low. These trucks HATE a low battery.

 

[Fless]

Forum tip: you can upload more than one pic in a single post. Also, if you shoot landscape mode the pics shouldn't have so much dead space above and below the scanner. It makes it easier for us to read.

The forum doesn't support uploading video, but you can host one on YouTube or the like, and post the link in a message here.

 

[SteelBaller3]

Forum tip: you can upload more than one pic in a single post. Also, if you shoot landscape mode the pics shouldn't have so much dead space above and below the scanner. It makes it easier for us to read.

The forum doesn't support uploading video, but you can host one on YouTube or the like, and post the link in a message here.

Got it, sorry about that.

 

[SteelBaller3]

All of them look like history codes to me.
KOEO clear all codes. Then look again, i bet they all will still be there. It just takes time for them to disappear.
I will usually get codes like that if the battery is too low. These trucks HATE a low battery.

I felt like it was the battery and put my deep cycle boat battery in it to just see what happened and the code went away. Also when I turned my headlamps off it seemed to go way up in voltage so I wonder if there’s an issue there? Like I said I had the battery tested at autozone and they said it was good 97% or something but I did have it on a trickle before hand. I’m going to take it to Napa tomorrow with alternator and have them tested together. I did start it on the deep cycle and voltage seemed better more in 13.5-14.5 range but still misfires when looking at the count. And could feel it. Also wouldn’t show voltage or readings at some sensors when looking at on board monitor.

 

[mikez71]

Lots of codes!

Cylinder de-activation codes should have all been disabled when the shop did the AFM delete..
Did you have any codes when the truck first left the shop?

You should have a check engine light with those codes..
Maybe old codes as @SpareParts mentioned..
Bad ECM's are supposedly pretty rare..

Looking at your pedal/throttle position log, I'm surprised you don't have a code for those too..
When it says "module not supported", looking at what?

 

[SteelBaller3]

Lots of codes!

Cylinder de-activation codes should have all been disabled when the shop did the AFM delete..
Did you have any codes when the truck first left the shop?

You should have a check engine light with those codes..
Maybe old codes as @SpareParts mentioned..
Bad ECM's are supposedly pretty rare..

Looking at your pedal/throttle position log, I'm surprised you don't have a code for those too..
When it says "module not supported", looking at what?

Yeah I’m confused on if these are codes from a long time ago or recent. They give no info about when they were logged.
When I am in the section to choose live data, on board monitor, etc there’s component testing for like evap system that works on my other vehicles. Idk even what to do next.
I bought it like 5 months ago and thought I was doing the right thing disabling the afm at a shop that’s well known for it with nothing but 5 star reviews.

 

[mikez71]

Possible those modules in scanner just don't exist for your vehicle?
(unless your other vehicles are the same and they do work)

Focus on the current recurring codes I guess..

Is your AFM deleted or just disabled?

And have you cleared the codes ever?

 

[Doubeleive]

typically that many codes indicates a short somewhere
voltage bumping up after start is 100% normal, it is done for like a minute and half (at least) to replace the power taken to start the engine, mine hits 15v+ everytime. (with 2 healthy batteries)
I would start inspecting all of the engine bay wiring, feel the wires with your hand and under the bottom where you cannot see, inspect extra careful any wires that rest on something
a flashlight may help to see in the shadows, look for any missing insulation, dark spots on a wire, melted wire, bare exposed wire.
if that reveals nothing then check the ecm harness pins for corrosion or water intrusion, same for under the fuse box.
then if still nothing go under it and look up under the engine and along the frame where the harness runs
then you can pull the spare out and check those rear modules as they can get corroded and have water intrusion also

 

[SpareParts]

Make sure you have proper battery voltage.
Hook up the scanner and hit scan all, when done, clear all. When done turn it off for about 10 seconds. Start it up. If no check engine light go for a drive
If the check engine light comes on then scan all again. Whatever module has the code it will turn red. That is the problem.

The codes under history are just that, history. Under Additional is just more history codes. You can not clear them or make them disappear.
A bad battery or alt will trip every one of them all at the same time. As soon as you have good voltage there is no longer a problem and they all get moved to History.
After so many cycles each get flushed out if not set again and the cycle restarts.
Right now all you're history codes are junk data caused by low voltage. History means nothing right now. Ignore it, don't look at it.
I have seen this so many times it not even funny anymore

Stop looking at history and focus on the current problem if you have one.
If P0621 comes back you have a weak/bad alt, battery or bad connection.

 

[SteelBaller3]

Make sure you have proper battery voltage.
Hook up the scanner and hit scan all, when done, clear all. When done turn it off for about 10 seconds. Start it up. If no check engine light go for a drive
If the check engine light comes on then scan all again. Whatever module has the code it will turn red. That is the problem.

The codes under history are just that, history. Under Additional is just more history codes. You can not clear them or make them disappear.
A bad battery or alt will trip every one of them all at the same time. As soon as you have good voltage there is no longer a problem and they all get moved to History.
After so many cycles each get flushed out if not set again and the cycle restarts.
Right now all you're history codes are junk data caused by low voltage. History means nothing right now. Ignore it, don't look at it.
I have seen this so many times it not even funny anymore

Stop looking at history and focus on the current problem if you have one.
If P0621 comes back you have a weak/bad alt, battery or bad connection.

Thank you for the information. Check engine light hasn’t come on one time since I’ve had it. The p0621 turns on battery light when koeo. When put different battery in, it didn’t. When scanned all systems, it showed clear in all. Had the battery tested again and napa said it is good as well. Having alt tested right now. Honestly hoping it’s bad. Might be a connection somewhere like you suggested though.

 

[SteelBaller3]

And alternator tested good in all categories.

 

[SteelBaller3]

Make sure you have proper battery voltage.
Hook up the scanner and hit scan all, when done, clear all. When done turn it off for about 10 seconds. Start it up. If no check engine light go for a drive
If the check engine light comes on then scan all again. Whatever module has the code it will turn red. That is the problem.

The codes under history are just that, history. Under Additional is just more history codes. You can not clear them or make them disappear.
A bad battery or alt will trip every one of them all at the same time. As soon as you have good voltage there is no longer a problem and they all get moved to History.
After so many cycles each get flushed out if not set again and the cycle restarts.
Right now all you're history codes are junk data caused by low voltage. History means nothing right now. Ignore it, don't look at it.
I have seen this so many times it not even funny anymore

Stop looking at history and focus on the current problem if you have one.
If P0621 comes back you have a weak/bad alt, battery or bad connection.

THANK YOU @SpareParts and @mikez71 and community! @mikez71 got me thinking about it not being a battery issue and more of throttle body/acc petal issue. @SpareParts got me to stop thinking about history codes and electrical issues. When I stopped focusing on electrical I believe I figured it out.
2 weeks ago it was idling rough and I cleaned the tb. I bought this scanner to relearn idle and it was still messed up. Then I stopped driving it and started messing with electrical. That’s when I got the charging issue message.
Last night I fully charged the battery on trickle charger, put it on and decided to do a throttle sweep which changed my actuator on the tb voltage to normal. It’s idling good for my test drive and has the power I remember.
Thank you everyone for all the suggestions it really helped me.