Delete Auto Stop/Start on 2025 (Not the temporary button)

[penright]

I was not thinking, BCM is probably checking the hood latch constantly for theft protection. I bet the code gets set unplugging it. That the pass/fail i thought it was me removing the bypass. May have to rethink the issue. Now I am more than ever curious what is under the heat shrink.

 

[penright]

It is wired how I would expect, except for the missing diode. The resistor measured about 2.4K

 

[PoManNox]

No light, i just saw the code when I connect the scan tool.

It's possible these harnesses throw the same or similar codes on my 2021 Equinox and Traverse. I only own an old $30 code reader which shows no present codes, but that may be because its not capable of reading those code families.

All I am concerned with is the MIL is not on, the A/S/S is disabled and everything else functions as it should on the vehicles.

 

[penright]

It's possible these harnesses throw the same or similar codes on my 2021 Equinox and Traverse.

Hard to tell. Until I can find some manufacturer information, it is all a guess.



Assuming GM did not change its strategy on A/S/S in the 2025 model. A false door ajar (closed) is required for the A/S/S to work. That is a big assumption. Something must have changed in the way signals are created. IE different resistor values and/or different pins. They have 2 signals so cars without A/S/S (KL9 option) for the hood ajar signal. One is to the BCM and the other is to the ECM. It makes sense that functions, like remote start, theft, etc are BCM and the A/S/S is an ECM function. If true that is why modifying the ECM signal only would not interfere with any remote start.

I will mess with it more tomorrow, but my best recollection is the ECM hood ajar was responding to the opening/closing of the hood. If true, I am guessing they swapped the pins. Again, I need to verify those observations. Of the 2 signal lines, the bypass passes pin 2 unmodified. That tells me that whatever signal can change with the hood opening/closing is what the pin (BCM or ECM) is connected to. If the modified signal is wrong, it should stay wrong. Right now that is my working theory and that is subject to change, either from experimentation or someone providing facts about 2025 schematics and/or operating strategies.

All I am concerned with is the MIL is not on, the A/S/S is disabled and everything else functions as it should on the vehicles.

Me too, I hope I can get there.

 

[2025blackout]

Hard to tell. Until I can find some manufacturer information, it is all a guess.



Assuming GM did not change its strategy on A/S/S in the 2025 model. A false door ajar (closed) is required for the A/S/S to work. That is a big assumption. Something must have changed in the way signals are created. IE different resistor values and/or different pins. They have 2 signals so cars without A/S/S (KL9 option) for the hood ajar signal. One is to the BCM and the other is to the ECM. It makes sense that functions, like remote start, theft, etc are BCM and the A/S/S is an ECM function. If true that is why modifying the ECM signal only would not interfere with any remote start.

I will mess with it more tomorrow, but my best recollection is the ECM hood ajar was responding to the opening/closing of the hood. If true, I am guessing they swapped the pins. Again, I need to verify those observations. Of the 2 signal lines, the bypass passes pin 2 unmodified. That tells me that whatever signal can change with the hood opening/closing is what the pin (BCM or ECM) is connected to. If the modified signal is wrong, it should stay wrong. Right now that is my working theory and that is subject to change, either from experimentation or someone providing facts about 2025 schematics and/or operating strategies.




Me too, I hope I can get there.

Looking forward to your progress. This is one of the first things I want to disable. I try explaining to my daughter I'd prefer she disable it when she drives it, but typical teenager it goes in one ear and out the other.

 

[penright]

I will mess with it more tomorrow,

Well, I did not mess with it. Just took a day off from everything. I did resurrect an old laptop to connect to my Hantek 8ch scope.

Looking forward to your progress.

I saw in another post you DYI wrench and have a friend who is a service writer. Do you think he could get us the schematic and/or theory of operations for the hood ajar? As you can see I have one for the 2024 and the bypass I bought should have worked. I am trying to find out what they changed in 2025 around the hood ajar. It would be nice to know definitively how it works.

 

[2025blackout]

Well, I did not mess with it. Just took a day off from everything. I did resurrect an old laptop to connect to my Hantek 8ch scope.



I saw in another post you DYI wrench and have a friend who is a service writer. Do you think he could get us the schematic and/or theory of operations for the hood ajar? As you can see I have one for the 2024 and the bypass I bought should have worked. I am trying to find out what they changed in 2025 around the hood ajar. It would be nice to know definitively how it works.

I'll certainly see if I can get that info!

 

[penright]

See if we can figure out if I am smoking something or if my logic sounds right.
I've been messing with 1's and 0's for so long that I may have forgotten Ohms law.

I measured the open (unplugged) current 2.1ma and voltage 5. If true then the pull-up resistor should be about 2.4k ohms.
Backprobed on the factory harness, Pin 1 2.2v and Pin 2 3.8V when the hood is open. Hood closed they are flipped.
Using the schematic to calculate the voltage divider assuming 2400 ohms is correct, then
732/(2400+732) = .233 of the 5v or 5*.233 is about 1.165v. which leaves 3.835. Which fits for the low ohm voltage.

But when I calculate the higher side ...
(1580+732)/(2400+1580+732) = .49 or the 5V or 5*.49=2.45 which leaves 2.55 Which is not what I expected. If the 732 ohm is right then the other has to be bigger than 1580. More like 1100
(2400+732)/(2400+2400+732) = .566, 5 * .566 = 2.83 which leaves 2.17

Again, unless I am smoking something, the bypass resistor should be 3.1k ohms instead of 2.4k.

I did confirm that pin 1 (yellow) was the hood ajar. Could not tell using the scanner, looks like the hood ajar PID was the hood ajar that shows on the dash. Changing pin 2 did not affect the PID or the dash message. So I am guessing the layout is close to the schematic I posted earlier.

All my resistors are at work, I think, and I not planning on being back till the 31st. If I had 4 days of vacation instead of 3, I could have been off the rest of the year. In case you all have not noticed, sometimes curiosity gets the best of me, and I may have to make a resistor run.

 

[penright]

I think I am going to wave the white flag. I finally backprobed the switch, discounted. It was 6.5K ohms. I verified the brown wire is the ECM. I found the hood data stream in the ECM on my scan tool. I could make/break a connection and get closed/open. Pretty sure I had the right one. With the yellow being passed through the dash hood open/close on the dash would respond. There must be more logic than hood open. Guessing they figured that it would not hurt to stop the engine with the hood open. Maybe all my testing got me confused. If no one else figures it out, then after a long brake might take another look.