Crazy Stuff on my 08 Hybrid Tahoe - Revs up and Dies

[tiktok4321]

This is an offshoot of another thread I started thinking I bricked my Tahoe after putting in an aftermarket radio. I since realized that I blew my BCU fuse. Replaced it and it started fine, but then redlines and dies. I've paid two mechanics to come out (because I can't take it anywhere) and paid each $150 to tell me that my hybrid battery needs to be replaced. I don't think that's really the issue. Another code that popped up was the P215B-00 - Output shaft correlation. I called the hybrid specialists who installed my battery and they don't think that the battery is bad. Unfortunately, they are about 45 miles away, so a hefty cost to tow if I need to take it back to them.

Could the output shaft sensor be causing the issue?

 

[j91z28d1]

how old is the battery? and it looks like a decent scanner, can you read the state of charge, the cell voltage and overall voltage. since you can't load the battery unless you start it,which is what your really need to know but that doesn't seem like a great idea to be doing. but if you did start it, logging those voltages, atleast the min and max cell voltage and maybe the current into the pack, to see if it's charging it like crazy could rule out the pack being dead the truck just trying to charge it. there's a gm tsb that has you Rev the poor thing to 3k for a max of like 20mins as part of a state of charge reset.

any time you pull the battery cables off for atleast 2 mins it resets the soc to 60% even if it was much lower to begin with. so it's possible to get everything out of sync. so the tsb is to run the truck till 70% state of charge, then remove then battery cables to reset it to 60%. can do that 2 more times of needed.

as for the code, not one I've seen. but give me a bit I'll research it and see if there's a troubleshoot walk thru. I still want to see a wiring diagram of this one bcm fuse circuit that blew too.


this might be a case where it's worth the money to get a month long diy all data access to the shop manual for your truck. I have access to a different shop software, so I've not seen all data but it should have all the same trouble shooting trees and walk thrus. I believe they are 30$ a month? or something like that. been a while since I looked.

I'll poke around my software later tonight.

in the mean time there's this, if you haven't seen it.

 

[j91z28d1]

took a quick look at your P215B-00 code it looks like it sets if there's a 10mph different between wheel sensor and output shaft speed. I'll upload the sheets later. I doubt you've been driving it so not sure how it set. unless there's a short it open in the wiring to it. does your scanner show freeze frame data?


either way that shouldn't case it to Rev like crazy. oh and I looked for that fuse. I'm guessing it's a body control module fuse, 10amp in the fuse box at the driver's side dashboard? that's all I see that sounds like it. the diagram shows it runs straight to the module. nothing else connects to the circuit along the way. honestly don't know if that's connected to this issue or not.

can you see the requested throttle position and the actual throttle position with your scanner under live data in the ecm? if so it should atleast narrow it down to if it's commanded high rpm or uncontrolled rpm racing.

 

[j91z28d1]

I feel like this isn't going to be of much help for you. but this is all I got for that oss code.

wait.. OK. so I just realized the scanner in the pic is probably the to guys you called out. in that case they needed to click into each of those faults and see what the code said. if I had to guess since there was one fault for each module, the fault code was probably something like lost communication with with the body control module because the fuse was blown. sadly that's probably useless to you, and the code for the oss, I wasn't paying attention, but if you read it. that code passed last test. there's no current fault in that sensor.

sorry to say man, at this point you're going to need someone who's better at trouble shooting new cars in general, hybrids more specifically. cause the regular guys are always going to blame the system they don't care to learn about. I agree with you that it's probably not the battery. you'd definitely need more data to completely rule it out but I don't see it there.

the only wild guess I have right now is to put the 12v battery on charge over night, and try it in the morning. these trucks are very weird about the 12v side and just having the key clicked foward one notch, before the radio even comes on is over a 10amp draw. if you had the radio on for even 15mins during the install without the truck running it can be flat.

oh and AAA plus gives you 4 free 100 mile tows a year. it might be cheaper to do that than one put right tow or finding another mobile mechanic. byond that you might need a China tech 2 and a crash course in diagnostic crap.

 

[tiktok4321]

Thanks for all your details - and you're right. The Scanner was the mechanic's and he's $140 long gone. Surprised he actually charged me (especially because he said if he knew it was a hybrid he wouldn't come out, but I clearly told him it was), but I digress. I have a jumping battery that I've had hooked up when starting it and it didn't seem to want to clear. It is a brand new 12v batt. State Farm will tow it to the local Hybrid mechanic. Gonna call and get that arranged today.

Before I send it, though, I'm going to put the OEM radio back in, disconnect the 12v overnight, cycle on/off a few times, and try maybe one more time.

I do know that it only takes one little computer to act up to infect all the rest of the computers. I feel like I'm just like one, little reset away from everything being OK. Or, from disaster.

 

[j91z28d1]

yeah.. those are both worth a shot forsure. I would hope just a factory radio change wouldn't cause all this. but at this point. nothing would surprise me with these haha.

after you let it set for a while with the battery disconnected you can touch the 2 cables together for a little bit too. that helps discharge any caps holding power. it helps with the ac issues on the non hybrid trucks too.

good luck man, I hope it's something simple they find. if you're doing to keep it away you might want to pick up a China tech 2. they are kinda invaluable in trouble shooting. I take mine with me on any road trips. can be had for about 300$.

 

[j91z28d1]

any luck with it? I'm super curious

 

[BG1988]

do a remote start then put the key in immediately then pop the hood... see if that will keep it going

 

[tiktok4321]

Alright - Wow. This Tahoe has been out of commission now for three months!! It's been sitting with my transmission guy for about 6 weeks now. For the first part of that, he was out with Covid. Hit him hard! He's back at work, though.

So, a recap of what's going on:

Back in Jan/Feb of this year, the CD player kept trying to eject a stuck CD. It wouldn't eject for anything. It was making an annoying sound, so I stuck a piece of cardboard in the CD slot and at least it was quiet.

That lasted for a bit of time but eventually the Tahoe wouldn't start up. I felt like it was my CD player that was draining my 12v just enough to not let it start. Eventually, I replaced my 12v. I soon forcefully removed my CD and then the head unit started acting ALL out of whack. So, I ordered an after market Android based radio.

When I went to install the radio, it started acting up quite a bit. I probably shorted something out because a lot of the plugs fit my vehicle harnesses. Eventually, my BCU fuse (tiny 2A thing) blows. Then I call for help. The guy comes out and reads my codes. We replace the 2A fuse, clear the codes, and the thing starts up, but less than 10 seconds later, it redlines, then shuts itself off. This repeats itself a couple of times, each time requiring a clearing of the codes. Mobile mechanic swears that it's a $40 sensor and he'll get to it ASAP. He ghosts me.

About a month later (April-ish), I get the Tahoe towed to my local Hybrid expert. He gets the same codes, says the sensor is located IN THE TRANSMISSION and he can't do anything about that. I get my transmission guy to tow it to his shop. He gets Covid and I don't hear anything from him for a month.

Then, about a week ago, he said he started it up, and there were no errors. No codes. He drove it 30 miles without a problem. Then, on the way back, he stopped it and started it again. Now, it won't move. It didn't rev, but it didn't want to move. He said it started throwing ABS codes. Now they're looking to see if it's the ABS module or the actual brakes that are faulting.

It just started working again after sitting for two months. So bizarre.

I bought a 2019 Suburban. Yes, I still have the HyHoe.

 

[j91z28d1]

wow. what a nightmare.

I feel like the only way you're getting this one fixed is to buy a clone tech 2 and dive into the trouble shooting yourself. shops are so bad with random stuff like this. it eats up time they could be billing other people.


my gut says it's ground issues. when it's multi systems and random like that. there's some bad ground point in all these gm trucks. even a non-insulated braided crown strap that likes to go bad if you're up north.


where are you located?