08 Tahoe Hybrid no start/ no crank after AFM valve replacement

[kenny-or]

Hey all, I'm looking for some help and thoughts on an issue I have been battling with my 08 Tahoe Hybrid. I recently had an issue with a collapsed AFM lifter so replaced all of the valves. Due to the cathedral heads I needed to remove the valve covers, Heads, Intake, Exhaust Manifolds, and the valley cover. In the process of doing the valve replacements I replaced the valley cover plate, the valves, the spark plugs and the gaskets. I also replaced the water pump as I noticed that there was a leak from the weep hole on the pump. Prior to removing any of these parts I disconnected the 12V accessory battery and then removed the disconnect from the hybrid battery. I had to pull the wiring harness from the top of the engine which runs from the left side to the right and connects to the Hybrid control box on the right side as well as the coils, fuel injectors, and a handful of other devices. There was 3 ground wires that were disconnected in the process which I have verified are all secure back in the original locations.

The problem I am currently facing is that upon reassembly the vehicle will not crank over. I get the radio and all other systems as though there are no problems. When I try to crank the engine I get no crank. I checked the power in the accessory battery which tests out at 13.2v. According to my scanner the hybrid battery has 12.4V (assuming that its the hybrid battery voltage that its showing me).

I get a Service Hybrid System on the DIC and no codes currently on the scanner. I have pulled and replaced the disconnect as well to ensure it was seated and clean.

Prior to the AFM valve issue the hybrid system was working flawless. Even during the AFM issue it had no problems.

Currently the scanner for voltage with key on shows:
vpwr ($00) 11.355
vpwr ($01) 11.355
vpwr ($02) 11.355
vpwr ($03) 11.355
vpwr ($05) 11.355
vpwr ($07) 11.355

With key off shows:
vpwr ($00) 0.049
vpwr ($01) 0.032
vpwr ($02) 0.000
vpwr ($03) 0.000
vpwr ($05) 11.562
vpwr ($07) 11.670

I believe that the first 5 of these vpwr are the hybrid battery banks and vpwr07 is the accessory 12v battery. These have lost some voltage since the last jump and testing.

I did jump the vehicle and used my multimeter to measure the voltage on the accessory battery at 13.4v and the vpwr ranged between 12.4-12.8v

I read that jumping the vehicle with the key on can cause the system to think that there was a collision which disables the crank. When I jumped the vehicle the key was off; however, I did turn it on after about 10 minutes charging to get the voltage levels. I can't imagine that this would have caused it to go into safety mode could it? I didn't jump the vehicle prior to trying to turn it over unsuccessfully. Only after it would not crank thinking that the voltage in the batteries may have dropped in the week it was disconnected while I was replacing the valves. I did check all the fuses with a multimeter to verify they were good and did not come across and bad fuses. I also disconnected and reconnected the plugs to the hybrid system after a visual inspection for corrosion or bent pins. Everything looks great.

I am at a complete loss on what to check or where to go from here besides finding a tech2 scanner to put the system in jump mode and disable the collision detection (if its on)... The scanner is fairly expensive and there are a lot of warnings about buying these and getting china knockoffs so thats obviously a concern.

Can anyone help or throw me some ideas on where to go from here?

Sorry for the long write up. I just wanted to give as much data as I could in hopes someone may have experienced similar issues or has some idea on what to do besides the tech2. I love this car but am pulling my hair out at this point.

 

[swathdiver]

View attachment 395441View attachment 395442


Hey all, I'm looking for some help and thoughts on an issue I have been battling with my 08 Tahoe Hybrid. I recently had an issue with a collapsed AFM lifter so replaced all of the valves. Due to the cathedral heads I needed to remove the valve covers, Heads, Intake, Exhaust Manifolds, and the valley cover. In the process of doing the valve replacements I replaced the valley cover plate, the valves, the spark plugs and the gaskets. I also replaced the water pump as I noticed that there was a leak from the weep hole on the pump. Prior to removing any of these parts I disconnected the 12V accessory battery and then removed the disconnect from the hybrid battery. I had to pull the wiring harness from the top of the engine which runs from the left side to the right and connects to the Hybrid control box on the right side as well as the coils, fuel injectors, and a handful of other devices. There was 3 ground wires that were disconnected in the process which I have verified are all secure back in the original locations.

The problem I am currently facing is that upon reassembly the vehicle will not crank over. I get the radio and all other systems as though there are no problems. When I try to crank the engine I get no crank. I checked the power in the accessory battery which tests out at 13.2v. According to my scanner the hybrid battery has 12.4V (assuming that its the hybrid battery voltage that its showing me).

I get a Service Hybrid System on the DIC and no codes currently on the scanner. I have pulled and replaced the disconnect as well to ensure it was seated and clean.

Prior to the AFM valve issue the hybrid system was working flawless. Even during the AFM issue it had no problems.

Currently the scanner for voltage with key on shows:
vpwr ($00) 11.355
vpwr ($01) 11.355
vpwr ($02) 11.355
vpwr ($03) 11.355
vpwr ($05) 11.355
vpwr ($07) 11.355

With key off shows:
vpwr ($00) 0.049
vpwr ($01) 0.032
vpwr ($02) 0.000
vpwr ($03) 0.000
vpwr ($05) 11.562
vpwr ($07) 11.670

I believe that the first 5 of these vpwr are the hybrid battery banks and vpwr07 is the accessory 12v battery. These have lost some voltage since the last jump and testing.

I did jump the vehicle and used my multimeter to measure the voltage on the accessory battery at 13.4v and the vpwr ranged between 12.4-12.8v

I read that jumping the vehicle with the key on can cause the system to think that there was a collision which disables the crank. When I jumped the vehicle the key was off; however, I did turn it on after about 10 minutes charging to get the voltage levels. I can't imagine that this would have caused it to go into safety mode could it? I didn't jump the vehicle prior to trying to turn it over unsuccessfully. Only after it would not crank thinking that the voltage in the batteries may have dropped in the week it was disconnected while I was replacing the valves. I did check all the fuses with a multimeter to verify they were good and did not come across and bad fuses. I also disconnected and reconnected the plugs to the hybrid system after a visual inspection for corrosion or bent pins. Everything looks great.

I am at a complete loss on what to check or where to go from here besides finding a tech2 scanner to put the system in jump mode and disable the collision detection (if its on)... The scanner is fairly expensive and there are a lot of warnings about buying these and getting china knockoffs so thats obviously a concern.

Can anyone help or throw me some ideas on where to go from here?

Sorry for the long write up. I just wanted to give as much data as I could in hopes someone may have experienced similar issues or has some idea on what to do besides the tech2. I love this car but am pulling my hair out at this point.

A Tech-2 is not expensive compared to what towing this to a shop will cost. It'll be a bargain.

I wonder if there are internal BCM codes related to the "Service Hybrid System" message. There may also be Failure Records to view on this as well.

Where do you live? We have a Tech-2 owner's thread where you can see if someone lives near you.

Your batteries all appear near dead. The under hood battery ought to be removed or placed on a trickle charger.

@RebelBelle

I didn't know that those 6.0 motors used the cathedral heads. Painting the VLOM looks cool. Is it new? It is SOP to replace the VLOM and lifter trays whenever the AFM system is repaired.

 

[kenny-or]

Thanks for your response swathdiver.​

I'll end up buying the computer if it comes to that long before I'll take it to the dealer. I'm sure I would end up needing it again at some point if I had to buy it. Wish my current scanner would work but of course they had to lock that out so only their scanner will access those specific items.

Yea its a new VLOM and trays. I try to follow SOP as much as possible. I'm not sure that painting it was really worth the time as it all gets covered anyhow but I like the way it looks lol.

What do you mean the hybrid battery is near dead? The highest I have ever seen those readings when the car was functioning correctly was in the 12-13v range as far as I can recall. It's my understanding that with the tech 2 you can put the car in jump assist mode and start it off the under hood 12v and i also read that without putting it into jump assist you cant get a charge to the hybrid battery itself; However, While I had cables on the 12v I watched the voltages climb into the mid 12's on the vpwr. I'm not 100% sure that the vpwn is the hybrid cell but I assume that's the case.

Even though the voltages seemed to come up I still got no crank after sitting on cables for about 20 minutes.

I don't see any code on my scanner but that doesn't mean they aren't there.

I'm located in Eugene Oregon. It would be awesome if someone had one near here!

 

[swathdiver]

Thanks for your response swathdiver.​

I'll end up buying the computer if it comes to that long before I'll take it to the dealer. I'm sure I would end up needing it again at some point if I had to buy it. Wish my current scanner would work but of course they had to lock that out so only their scanner will access those specific items.

Yea its a new VLOM and trays. I try to follow SOP as much as possible. I'm not sure that painting it was really worth the time as it all gets covered anyhow but I like the way it looks lol.

What do you mean the hybrid battery is near dead? The highest I have ever seen those readings when the car was functioning correctly was in the 12-13v range as far as I can recall. It's my understanding that with the tech 2 you can put the car in jump assist mode and start it off the under hood 12v and i also read that without putting it into jump assist you cant get a charge to the hybrid battery itself; However, While I had cables on the 12v I watched the voltages climb into the mid 12's on the vpwr. I'm not 100% sure that the vpwn is the hybrid cell but I assume that's the case.

Even though the voltages seemed to come up I still got no crank after sitting on cables for about 20 minutes.

I don't see any code on my scanner but that doesn't mean they aren't there.

I'm located in Eugene Oregon. It would be awesome if someone had one near here!

I think @Rocket Man lives in or near Eugene. I had the opportunity recently to run my Tech-2 on two hybrids like yours. I don't remember everything I saw but it was pretty cool. Those key off numbers don't look good but I don't remember exactly what they mean.

Brent and Gene have hybrids and they may take a day or so to respond.

 

[kenny-or]

Thanks for the suggestions. It would be awesome if there was someone close that could help me out. Lord knows I don't want to buy a computer right now but I guess I will have to plan for it in the near future here. Then I can at least be another resource for others that don't have one and need help. The situation is a bit odd though... It really doesn't make sense that it would suddenly die after having no issues with it prior which makes me think maybe there is a broken wire or something but I don't even know where to start to investigate that. I think from here the next step is the scanner to narrow down the issues unless anyone has any additional ideas?

In regards to the power being out to those cells with the key off, I believe that is normal from what I recall seeing before this while playing with the scanner on it.

 

[Rocket Man]

Unfortunately Eugene is about a 2 hour drive each way from Portland where I live. If you want to make the drive I’d be glad to see if I can help with my Tech2.

 

[TollKeeper]

His truck would need to run for him to make the drive..

My understandings of the Hybrid system for jump start is that you have to put a charger on the assy battery, and let it sit there for a good 4-24 hours at 12ish amps. This is so that the HCM can trickle charge the Hybrid battery pack, since the starter is only powered by the Hybrid battery pack.

What you have going on is very typical of a dead, or near dead, Hybrid Battery Pack.

The charge may work, it also may not work. And at this age, if it did go dead, is it going to take a charge.

May have to look into replacing the Hybrid Battery Pack if it wont take a charge.

Would need a Tech2 to know whats actually going on.

 

[Fless]

I think @OR VietVet might be near Eugene, IIRC?

 

[kenny-or]

Hey RocketMan, as TollKeeper said the car is not capable of traveling currently unless I put it on a car trailer which I have half a mind to do at this point but I would have to check with some friends about them helping me achieve that. I'm starting a new job slinging parts for BnR on Monday so am really trying to get it going before then if possible. It would certainly be easier to move the tool then the car. Would you mind posting a link to the specific tool you have? Would you consider renting it to me for a day? I could maybe leave something for collateral like my ring or something. I think I'll trickle charge it for a day or 2 first to see if that works though. I wouldn't be able to make the trip until the weekend anyways as I would need to steal my wifes car for the trip and she requires it for work. She runs an after school program so has to travel between sites.

TollKeeper, Thanks for the input. I'll get it on a charge for a few days and see if that helps. I'll post back about results.... hopefully the battery didn't faceplant; However, I would open it up and replace the bad cells which from what I priced run about $50-60.

Fless, It looks like OR Vietvet is located up near Portland as well by the falls. I'm prior military myself but it is a few hours between Eugene and Portland which raises the same issue as with RocketMan. I greatly appreciate the suggestion though!

 

[Rocket Man]

OR Viet Vet was in Eugene, I don’t know if he’s still there. Send him a PM. Sorry but the only way I let any of my tools out of my sight is if I get a cash deposit equal to the value of the tool, I used to loan tools and learned my lesson. You can buy one on EBay but it will take awhile to get it depending on if you can find a seller with one in the US. Most are selling from China. Chinacardiags is the seller I used. I would send a PM to VietVet and see where he lives. There’s also a couple other devices others here have used that simulate a Tech2, I’m not familiar with them. Somebody else might chime in. Sorry, I didn’t read the entire thread before I posted about driving up here, didn’t realize it wasn’t running. I just saw somebody had alerted me.

 

[Rocket Man]

I just checked the Tech2 owners map and OR VietVet apparently doesn’t own a Tech2. I’m the only one in Oregon that I see. There’s a PDF that’s kept updated, click on it to see the list.

Tech 2 Owners Map

There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...

www.tahoeyukonforum.com

 

[j91z28d1]

looking at your post, my first thought was did you click the extra little tab on the hybrid plug? it's simple but very common to miss it. you put the plug in and there's a extra tab you gotta click. there's a YouTube video if need be. but you'll. probably known if you did it.


I don't believe those are your hybrid cell voltages. there's 20 of them. alone with Temps that are good to monitor. they will tell you a lot about hybrid battery life. just buy a 300$ tech 2 if you own this truck for any amount of time. it's worth it, use the china link, I have it and it's priceless for trouble shooting. you can't even follow a trouble shooting tree without one. my truck has 30 modules in it to read. most scanners read one. my 3k work scanner reads about 10. the china tech 2 reads them all, with live data.

in the mean time, and for daily monitor I like using the torque app. if you have an android and 30$. you can add a bunch of pids for the battery cell voltages, Temps, current into and out of the pack while driving. fan speeds. stuff like that. you can't read the battery fault codes with it thou. well you probably can but I don't know how, the tq app message board is full of people smarter than me lol.

these trucks are very touchy about starting, anything out of sequence with the hybrid system will keep them form cranking, and it checks everything every time it starts. so yeah, gotta get some battery data, but especially the fault of code that prevents it from starting and go from there. in the mean time double check everything you removed. and charge the 12v battery out of the truck. like that plastic cover over the hybrid box under the hood. there a jumper in there that will keep it from starting it not installed. if the main orange plug is correct. anything hybrid related has a safety built in, so nothing is energized unless it's perfect.


how many miles and what year is your hybrid pack? how long was it apart since it last ran? if you're over 80k and 8 years, it's probably on its last leg. there's a section over on a electric car board, (mostly prius) that if you data log the battery under load using tq app, like max ac with window down and full accessories on. they will graph out your pack voltages and give you an idea how's its doing. but 99% of the time the center cells of the pack is damaged. it's made by the same company that built the prius packs, but horribly over used by the gm software and under cooled. so the packs don't make the 200k a prius does. normally by 140k yours struggling to drive the thing safely.

 

[j91z28d1]

A Tech-2 is not expensive compared to what towing this to a shop will cost. It'll be a bargain.

I wonder if there are internal BCM codes related to the "Service Hybrid System" message. There may also be Failure Records to view on this as well.

Where do you live? We have a Tech-2 owner's thread where you can see if someone lives near you.

Your batteries all appear near dead. The under hood battery ought to be removed or placed on a trickle charger.

@RebelBelle

I didn't know that those 6.0 motors used the cathedral heads. Painting the VLOM looks cool. Is it new? It is SOP to replace the VLOM and lifter trays whenever the AFM system is repaired.

yeah the 6.0 has the cathedral port heads, I've always heard they make more mid range than a rec port on the 6.2's, so kinda makes sense. that an they have a higher compression ratio, to help off set the late intake valve closing cam. I forget the name of that, but it's also gives up off idle tq for mid range efficiency. the electric motors help cover for the lack off the line power for the extra mpg from the late intake closing setup. that and the tranny is veriable ratio is a weird way, it will let the engine flash into its power band quicker too.

 

[kenny-or]

RocketMan: I totally understand not letting your tools go. I have learned that lesson as well but figured there was no harm in asking even is the chances were slim. I actually thought the scanner was significantly more expensive then $300. I had read on some other sites that the cheap ones were not the true scanner and that they actually cost around 2k. I was confused by this as I couldn't locate what they claimed I needed which is why I was asking. My current scanner cost me more then the tech2. Granted I don't have the extra cash to buy one this minute but I will soon hopefully. Then y'all can add me as the guy in Eugene with one lol.

j91z28d1: Thanks for your response and suggestions. I can only imagine your talking about the retaining clip that locks the plug into place? I'm not sure what other "tab" you would be referring to. My Tahoe has 265k miles on it but I have only put the last 30k on it. The vehicle was owned by the government prior to and had an extensive set of maintenance records. I have an Iphone but may get an android just to get the torque app. I'd love to data map the battery loads and so on. I think I read this vehicle has 15 batteries that make up the battery pack. Each battery cost about $50-60 to replace so if I find that some are bad I'll replace the dead cells. The car was apart for about 4 days while I replaced the valves. Outside of the valve compressing about 2 weeks ago the motor and the electric mode have been working perfect. I just cant imagine that the pack would have gone bad after 4 days of not being used when it has worked fine up to now. I do have it on a trickle charger now. Hopefully it can get it charged up and start. The cathedral heads are a pro/con when it comes to replacing the valves haha.

 

[kenny-or]

I'd still love to see a couple links to what you guys would suggest I purchase scanner wise if you wouldn't mind

 

[j91z28d1]

with that milage, it's forsure been replaced. I do think a few days of being apart is fine. I think you're missing something when putting it back together.

I've rebuilt my battery, not using oem stuff, but your battery as 40 cells in it and a voltage monitor per 2 cells, so it will read as 20 modules. has 6 temp sensor, one in the intake port, one on the exhaust and 4 on the batteries themselves. when your battery goes, the truck will start to jerk as it starts the engine while moving the truck coming out of auto stop. it will be worse on hot days when max ac is on.

I'm a bit confused. you replaced the afm lifters with new afm lifters but also replaced the valves in the heads? I understand that's a lot of mileage, and you can have some valve guide wear, but I've not heard much of replacing the valves themselves?

I'll look for the links in a few mins, there's a app I believe works in iPhone, but it's not customizable to add pids, and I can't test it, but I believe it might tell you cell voltage as well. you can try it with the same 30$ obd2 blue tooth scanner.


what scanner do you currently have? will it show anything under a different section? if it's more than 300$ I'm a bit surprised it doesn't do anything more than the ecm.

 

[j91z28d1]

scanner..

this is what most people get I have it and another one that works but this the most link I got mine from.

for Android Phones ONLY - Wireless Bluetooth Diagnostic OBD2 Scanner Car Code Reader and Scan Tool for All 1996 & Newer Vehicles ELM327 Compatible OBDII https://a.co/d/7BEKQYJ


this is what the app looks like on my end that might be in the apple store, hopefully you have the same one on the IPhone side. or someone that has a cheap old android based anything you can borrow.

 

[j91z28d1]

this is the latch I was talking about. o
you. probably did it right, but just incase

here's a link to the tech 2 I bought, i got it off this site. in the long tech 2 thread.

Cheap GM Tech2/ Saab Tech2 Diagnostic Scanner Full Package

GM TECH2 Scanner Full package comes with free TIS2000 Software, you can choose one kind of software for GM, SAAB, OPEL, SUZUKI, ISUZU, and Holden.

www.chinacardiags.com

it will take like 2 weeks to ship, it comes straight from China DHL.

I'll attach a pic of what I monitor for hybrid battery voltage using tq app and a pick of inside the hybrid pack. I don't really think a dead pack is your issue thou.

 

[Rocket Man]

As far as the Tech2, the Chinese clones are what most of us are using. The company that makes them is the same company that used to make them for GM from what I understand. The link above is where I bought mine. It does take some time to get it. I heard of others finding US sellers but last I checked on eBay there weren’t however you might get lucky. You just have to make sure it has the latest version number. Chinacardiags is the safest way imo.

 

[kenny-or]

with that milage, it's forsure been replaced. I do think a few days of being apart is fine. I think you're missing something when putting it back together.

I've rebuilt my battery, not using oem stuff, but your battery as 40 cells in it and a voltage monitor per 2 cells, so it will read as 20 modules. has 6 temp sensor, one in the intake port, one on the exhaust and 4 on the batteries themselves. when your battery goes, the truck will start to jerk as it starts the engine while moving the truck coming out of auto stop. it will be worse on hot days when max ac is on.

I'm a bit confused. you replaced the afm lifters with new afm lifters but also replaced the valves in the heads? I understand that's a lot of mileage, and you can have some valve guide wear, but I've not heard much of replacing the valves themselves?

I'll look for the links in a few mins, there's a app I believe works in iPhone, but it's not customizable to add pids, and I can't test it, but I believe it might tell you cell voltage as well. you can try it with the same 30$ obd2 blue tooth scanner.


what scanner do you currently have? will it show anything under a different section? if it's more than 300$ I'm a bit surprised it doesn't do anything more than the ecm.

j9: Great info! Sorry for the confusion, I replaced all of the lifters not valves, I misstated. My current scanner is a Actron cp9690. Oh, in regards to the latch, I did get that secured properly but I can see how people would over look that.
I do feel like I am missing something in the reassembly but I have gone over it 100 times and can not find anything... That's what brought me to the forums to post for the first time.
My daughter has an android so I will just borrow her phone to play around with the apps.


RocketMan: I'll take a look to them when I have some cash for that. Hopefully it will not take me to long.