How to disconnect aux battery?

No such connectors on my '02 aux. batt. You can remove the ground (black) cable by loosening the clamp nut with adjustable or socket wrench, and leave the positive side alone. (N.B. I long ago replaced the factory battery cable clamps with SAE (American) battery clamps so I could install a domestic 12V battery. No need to pay big $$ to the dealer for a replacement: just something to keep in mind when your aux. batt. goes.)

The red cover on the positive side is held on by two (or three?) tabs which can be released by inserting a screwdriver blade and twisting. Or you can simply yank the thing off by hand. Use caution around those slender wires!

 

Here is a shot of the battery clamp assembly on a Gen 1, with the red cover removed.



Pay no attention to the fat red wire coming off the bottom; that's not stock. (The picture was from a thread where I added that. I attached it to one of the bolts holding the legs of the big fuse. Normally you can't see that bolt because a flap of the black plastic covers it.)

Notice that fat black-with-green-stripe wire at the top. It has a squeeze-to-unplug connector. That's what supplies power to the car.

If you look closely at the other side of the clamp assembly (the right, in this picture), you see what looks like a flat black ribbon coming down, with only one skinny wire in it, which plugs in with its own smaller squeeze-to-unplug connector.

That is a separate circuit that is only used by the car to measure the battery voltage and control charging. You probably don't need to unplug that to cut car power and forget trouble codes. It only goes to a voltage-measuring circuit in the converter under the hood. But if you feel like unplugging it too, that's not a problem.

Taking one step back to the "why are you doing it?" question: have you read the trouble codes yet that explain why your check engine light is on? The car will, of course, forget them when you do this, and if you didn't read them first, then you will be delayed in solving the problem. You won't get more information until the ECM re-detects the problem, which can happen quickly for some issues, but could delay you by weeks or months for others.

 

i think gen3 has white plugs on 12 v to quickly reset. not us 2

 

It's the other way around. Gen 1 and Gen 2 use a positive-clamp/fuse-block assembly back on the battery, where there are two squeeze-to-unplug connectors. The fat one is the power connection, and the skinny one is for battery voltage sensing.

Gen 3 still has a fused positive-clamp assembly, but nothing you can squeeze and unplug. However, Gen 3 has a fat white connector in the underhood fusebox that you can unplug.

The photo of a Gen 1 battery clamp in post #3 above is not a deepfake. It has squeeze-to-unplug connections.