so I have seen this talked about but never actually done. so I decided to try it for a while and see how it works. I can say it works perfectly.
so back story for those they don't know. the main hybrid battery pack runs just about everything and gm designed the air cooling system badly, as in they didn't do anything to cool it at all. this is basically a prius pack with extra cells. Toyota put thought into the cooling on the prius and they go 200k on oem packs and will sell you a new one even today. gm did nothing but use the fan inside the case, and it slows down as the truck comes to a stop so you don't hear the fan running. our packs last 100k at best.. probably starting to give you issues by 80k.
so it's mostly impossible to buy a new pack from gm. the factory still exists, Toyota owns a part of it. which is the only reason they are still using nickel metal hydride technology, but anything you buy 3rd party like say green cubes is going to be battery's from junkyard cars run thru a referb process. I see as much as $4k for these packs.
signs of a weak hybrid pack, besides check engine light. is bucking as the engine starts when taking off from a stop sign, it's trying to drive the truck with one motor and start the engine with the other. if the pack is weak, the voltage crashes and the system shuts down, bucking and jerking.. I've seen posts when it's really bad it can try to Rev the engine to keep itself running, all while taking 2 feet on the brakes to keep it from driving thru stop signs. unstable voltage the other way can happen to, as when cells get weak and charged the voltage jumps up higher for the same current put in it. if this gets to the point that any one cell(2 modules) hits 20.4v for 4 seconds it will open the main contactors in the hybrid battery. at that point your whole truck shuts down, and since it's usually during braking, it's in the middle of traffic in rush hour. not fun. oddly it will usually throw a code for 42v lost to steering system when this happens, because technically it did, but because the hybrid cell over volt not a steering issue. which you'll need a tech 2 and scan thru the freeze frame data to find. usually this fixes itself as soon as you cycle the key and the voltage drops below 20.4. which it will. but it will get worse. point being these aren't really safe to just keep. driving on a dying pack.
so the hood switch trick is mainly for when your hybrid battery is weak and you don't want to buy a new one. side effect I found is it actually drives nicer and doesn't loose much mpg from not going into auto stop all the time.
I'll up load the diagram for anyone that wants to try it. the hood switch is wired so that the ecm knows if you just disconnect the plug, and throws a fault code. so you will have to jumper terminal a and d together(leaving be open) to tell it the hood is open when it's not.
I put a 3 way switch on mine, so I can flip it one way to work like normal, and the other way to bypass and tell the ecm it's open at all times. the plug is a few inches to the right of the hood latch as the easiest way to get to the wires.
can provide more info to anyone they needs it
so back story for those they don't know. the main hybrid battery pack runs just about everything and gm designed the air cooling system badly, as in they didn't do anything to cool it at all. this is basically a prius pack with extra cells. Toyota put thought into the cooling on the prius and they go 200k on oem packs and will sell you a new one even today. gm did nothing but use the fan inside the case, and it slows down as the truck comes to a stop so you don't hear the fan running. our packs last 100k at best.. probably starting to give you issues by 80k.
so it's mostly impossible to buy a new pack from gm. the factory still exists, Toyota owns a part of it. which is the only reason they are still using nickel metal hydride technology, but anything you buy 3rd party like say green cubes is going to be battery's from junkyard cars run thru a referb process. I see as much as $4k for these packs.
signs of a weak hybrid pack, besides check engine light. is bucking as the engine starts when taking off from a stop sign, it's trying to drive the truck with one motor and start the engine with the other. if the pack is weak, the voltage crashes and the system shuts down, bucking and jerking.. I've seen posts when it's really bad it can try to Rev the engine to keep itself running, all while taking 2 feet on the brakes to keep it from driving thru stop signs. unstable voltage the other way can happen to, as when cells get weak and charged the voltage jumps up higher for the same current put in it. if this gets to the point that any one cell(2 modules) hits 20.4v for 4 seconds it will open the main contactors in the hybrid battery. at that point your whole truck shuts down, and since it's usually during braking, it's in the middle of traffic in rush hour. not fun. oddly it will usually throw a code for 42v lost to steering system when this happens, because technically it did, but because the hybrid cell over volt not a steering issue. which you'll need a tech 2 and scan thru the freeze frame data to find. usually this fixes itself as soon as you cycle the key and the voltage drops below 20.4. which it will. but it will get worse. point being these aren't really safe to just keep. driving on a dying pack.
so the hood switch trick is mainly for when your hybrid battery is weak and you don't want to buy a new one. side effect I found is it actually drives nicer and doesn't loose much mpg from not going into auto stop all the time.
I'll up load the diagram for anyone that wants to try it. the hood switch is wired so that the ecm knows if you just disconnect the plug, and throws a fault code. so you will have to jumper terminal a and d together(leaving be open) to tell it the hood is open when it's not.
I put a 3 way switch on mine, so I can flip it one way to work like normal, and the other way to bypass and tell the ecm it's open at all times. the plug is a few inches to the right of the hood latch as the easiest way to get to the wires.
can provide more info to anyone they needs it
