Car battery Light & sounds light crap & boils over

The connection to what? The scanner’s connection to the ECU?

You mean put a reader under the steering wheel or the actual ecu underthe hood

Plug a reader into the obd 2 plug under the steering wheel. Turn the ignition on. Can it connect to the ecu?

Before all these problems my buddy obd would not bring up any codes on his device it was registering as if the car didn’t exist that was even when the check engine light was on at that time but this was weeks ago. Reason for that engine light on was because one of the valve tube was forgot to put in. Then ever since check engine light never been on even now. Only battery light. I took the ecu out and looked at it didnt see any thing wrong with it from my eyes and couldnt take the back metal plating off because it glued on there

From what I can tell the PCM is what turns on the battery light. It bases its decision in part on a pwm input from the alternator, GY/YE wire. If the alternator warning light wire (LG/RD) was accidentally shorted to chassis ground it would turn on all the time the key was in on or start, despite what the PCM wanted. So that’s another thing to check. Charging systems have become quite complicated these days. If the normal diy’er checks (checking connections, grounds, etc) don’t solve the problem you’ll probably have to either secure the factory service diagnostic procedures for the charging system or hire an experienced shop to solve it for you.

Well there is your problem. Dead ECU

And you can’t see a failed ECU.

Ive had 2 professional mechanics look at it & they dont even know why the battery light staying on. But were narrowing it down thinking sensors, wires or maybe something else. All the ground wires are good.

Mechanic looked at it with scanner & few scanner software even the hp tuner one. An there no codes. The ecu is good. Voltage good. Etc when car cold the car starts but when hot it shuts off while sounding like crap. When i take temp sensor off and plug in the car remains on idle at 1300 rpm & battery light still remains on sounds like the car how it should run but press on acceleration or shift gears it dies

Since you replaced the alternator it seems something else is getting power to the battery warning light. Normally power to that light should be controlled by the ignition switch. To verify that the alternator isn’t back feeding voltage to it remove the small wire connections at the rear of the alternator and see if the light goes out then. If it does then something within the alternator may be allowing that to happen. A bad blocking diode perhaps. You should also see if the LAMP lead for the alternator has voltage on it while the ignition is OFF. It shouldn’t have voltage there.

Were would this blocking diode be located? and i tried unplugging the alternator wire then plug in but battery light remains on.

Inside the alternator, there are 6 of them.
I’m guessing your new alternator is bad.

Alternator good. The flow of current is good to the battery. I just dont know why my battery light wont go off at all

You stated you removed the wiring to the alternator but it sounds like you didn’t check to see if the warning light turned off when you did that. If you did check the light while the connection was removed and the light stayed ON then the trouble isn’t with the alternator. If you have an external regulator then try removing the wiring to it and see if the light goes out. If none of these work to turn out the light then you most likely have a problem within the dash cluster.

Today before messing with it at all. I turn it on while cold. The rpm was sitting at 1100 i went to check the battery and alternator voltage. It went up to 14.43 volt on alternator & 14.31 on battery. When i check the coolant temp sensor plastic wire it was getting 0.30 volts & this wire also goes to the starter. When i check the battery light it was off this time & running like normal at 800 to 900 rpm at idle. The weather is 50F. I took it for test drive and didnt shut it off at all while out. Get home wait few seconds. Turn off then turn on Battery light came back on. Check the voltage. Alternator was 13.43 , battery was 13.31. The coolant temp sensor wire that goes to the start was 0.00. I tried to turn the lights, air on max & radio & it sat firm without moving

Also while battery light on the second time trying press gas pedal shuts it off

I assume in your last post you are saying that pressing on the gas pedal while the engine is running caused the warning light to turn off. That would indicate something inside the alternator isn’t right.

If the light is On while the ignition is OFF, then you need to follow the instructions I gave to you in my previous posts to see if there is a problem outside of the alternator.

Warning light remains on the car rpm drops and shuts off when i press gas pedal. Warning light stays on.