probably a short or break in the lan bus somewhere
What did you do to your NNBS GMT900 Tahoe/Yukon Today?
- Thread starter phattyford
- Start date
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oh haha.
it's a hybrid thing, if the hood is open the truck doesn't go into auto stop, the engine runs while the hood is open. it's mentioned a lot over the years as a way to bypass aurostop on the different hybrid groups. but since it's a bit extra, you need the diagram to sort it out so it doesn't throw codes.
I decided to try it out it curiosity
Charlie207
Full Access Member
Step 1 was putting eyes on the ABS/EBCM module. Thanks to whoever provide the physical location of that thing; it's along the frame-rail under the between the driver's doors. Now that I have a starting point, I can lift up the car, and start looking for physical damage to the loom & wires.
The harness to the ABS/EBCM module was fine, and far enough back that it was never touched during the engine swap. But as I looked forward, it runs up over the front driver's inner fender liner, and I wonder if something got yanked on.
I'm also going to flash the last 5.3 tune just to rule out any software goofiness.
probably need to verify the can bus network is intact, a incorrect ohm reading is one clue.
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Charlie207
Full Access Member
Bought a 2-ch sillyscope from the jungle website. It's another tool to have to help troubleshoot the ABS stuff, plus I'm hoping I can make cool sine wave tones with it. (maybe figure out a way to reeeeeally set up the intonation on my guitars)
gooffeyguy
Tom
Peterson Stobe Tuners work great for intonation on guitars. I have a StroboPlus HDC
kbuskill
***CAUTION*** I do my own stunts!
I'm not sure about the GMT900s but the GMT800s had issues with solder joints inside the ABS module.
kbuskill
***CAUTION*** I do my own stunts!
Kind of defeats having a Hy-bird don't it?... lol
Seems like that is something you could turn off with HP Tuners.
it's a very long story but basically I'm just testing stuff. in theory it would make a big difference in mpg, but on the other hand these aren't plug in hybrids. there's no free lunch, the only real things that lead to more efficiency is the type of cam design run in the engine, the engine itself being smaller bore than the 6.2 and the heads being Cathedral style might be more efficient at low rpm tq. (this engine lives between 1k and 2k rpm) it's also aluminum to save weight. they made the tahoes better aero and lighter aluminum hood and hatch but not the yukons and Escalades. the tranmission itself is a pretty good design to keep the rpm band tight and can use the battery power to help move the truck but that power mostly only comes from regen braking and the rest from the engine anyways.
so say you're stopped for a while, long light or drive thru. it's running tons of stuff off the battery, the ac of course being the most load, but there's 3 extra coolent pumps the internal hybrid battery fans, the electric transmission fluid pump. I've seen over 4kw in auto stop, all that runs the battery down from say 60% state of charge to 45%. light turns green, you take off, it starts the engine and will use a bit of battery power to get you going off the stop, the less the charge the less it assists. soon it's pretty much driving the car and charging the battery up, trying to get back to that 60% for the next stop. max charge being 70% but only when forced, it targets about 64%, when it's above 60% it discharges noticeable more during acceleration. which is what it seemed to set at more of city driving today.
so all said, if you keep it from turning off all the time, you'll give up a bit of fuel at idle but make it up by not having to charge and still using the regen. so I decided it was an interesting question. that and when it's 111deg outside here the ac is taxed hard, when in auto stop it backs down the ac compressor rpm to help with battery load,(I guess) when engine running it doesn't and the ac has a little more crispy feel to it.
I also wanted to know if the truck was OK with it, I have a good battery but for people with slowly failing hybrid batteries, these trucks absolutely hate it. run bad, jerk all around and can get to the point to me it's unsafe. forcing it to run the engine all the time would allow these people that don't want to spend the money on a replacement battery to limp it along much longer. (hopefully till lifters eat the cam anyways) at that point mph could take big hit but worth it to most average people that bought a hybrid without realizing what they just got into haha. everything is complicated, expensive and discontinued. with it running all the time the only thing the battery would really be asked to do is start the truck once at the beginning and since your state of charge will be higher than it normally is. it can do that well passed what normally is undriveable. if you say pull into your drive way and the battery happens to be low end 45ish% when you walk out in the morning to start it. if any one cell is 1.5v more or less than the other, it throws codes at best. gives you electrical gremlins at worse.
driving it around today, unless mileage really tanks, it's pretty nice to drive. the hybrid battery discharging a full 15kw getting up to speed makes for a much smoother drive.
edit* I'd love for hp tuners to be able to do it. I have it and the ecm is unlocked but there's not much defined in there, very basic stuff. I only really did it for afm disable but I do have a test timing table in it right now too. the ecm on a normal truck kinda runs the show, on a hybrid the hybrid controller runs the show. your throttle pedal request an amount of tq and it decides how much to request from the electric motors, and the how much to ask the ecm for. as of now no one had cracked or even wants to hack the hybrid modules of any car. the tuning would definitely be complicated and almost no one with a hybrid thinks of it as anything more than an appliance. they are just a blender or microwave that sits in the driveway instead of the counter top. the market just isn't there to spend the development money on. which is kinda a shame.. maybe some day with the eray corvettes but even then, corvette guys usually think any mods away from what gm intended are unthinkable.
