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Vehicle Speed Sensor Location 2008 4wd

nyjumpee

nyjumpee

Full Member
Joined
Jun 20, 2010
Messages
49
My 2008 Avalanche 4wd 5.3 starting shifting rough from 1st to 2nd. A few days later my Check Engine light came on with a P0717 code. . .Vehicle Speed Sensor should be replaced. $30 at Autozone. . .my question is WHERE IS IT!? I've gotten a few different answers "on the side of the tranny". ."on the back of the transfer case". . .neither of these places to I see something that looks like the replacement part from Autozone. I've youtubed. .I find Suburban, tahoe, etc. and I've looked where they say to look. . no luck. . .any help? Thanks!
 

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It's hard to see it because it's sort of hidden up on top of the transfer case. (Part 13 in the diagram)

19302667.JPG
 
PS the code does not men the sensor is bad... means that system has an error and needs checking.
There are proper troubleshooting guides out there for codes...
www.engine-codes.com

P0717 Chevrolet: Code Meaning, Causes, Symptoms, & Tech Notes

The Input Speed Sensor detects the primary pulley revolution speed and sends a signal to the Transmission. The Input Speed Sensor (ISS), also known as the
www.engine-codes.com www.engine-codes.com

So check harness and connector before replacing
 
ca2kjet said:
It's hard to see it because it's sort of hidden up on top of the transfer case. (Part 13 in the diagram)

View attachment 230816
Click to expand...
Thanks ca2kjete! That diagram definitely made it MUCH easier. . .I found it and replaced it. . .that's the good news. . .the bad news is that it didn't clear up the issue. . .it's intermittent. . .sometimes it's fine and other times it shifts rough. . .I'm guessing it's a connection issue. . .or another sensor?
 
ygmn said:
PS the code does not men the sensor is bad... means that system has an error and needs checking.
There are proper troubleshooting guides out there for codes...
www.engine-codes.com

P0717 Chevrolet: Code Meaning, Causes, Symptoms, & Tech Notes

The Input Speed Sensor detects the primary pulley revolution speed and sends a signal to the Transmission. The Input Speed Sensor (ISS), also known as the
www.engine-codes.com www.engine-codes.com

So check harness and connector before replacing
Click to expand...
Thanks YGMN. . .and you were correct. . .I did manage to find the sensor with the help of the diagram provided by 2kjet. . .and it didn't fix the issue. The connector that goes into the sensor looked clean and didn't see any wiring issues with the limited view that I was able to get. And it is intermittent which would seem to indicate a bad connection. . .it's just tracing the thing that's going to be a problem. . the wire goes up and disappears. . .One interesting thing I noticed is that the first time that I drive away from the truck being turned off, it shifts fine into 2nd. . .after that it's rough. Every time! Anyway, any suggestions on exactly what, where or how to check the connections/wiring? Thanks again and good call on the actual sensor not being the issue. . .just wanted to eliminate that from the equation.
 
check grounds
 
thread in here somewhere shows grounds...

look under PROBLEM SYSTEMS
 
Hi! I have an 08 LTZ 4WD 5.3 with about 235k and new tranny about 70k ago and no longer under warranty. A few days ago I noticed rough shifting between 1st and 2nd. After a day my check engine light came on, checked and got P0717 code. I replaced the VSS located on the top of the transfer case here. .it's #13
AvalancheTransferCase.jpg
Before I actually replaced it, I first crawled under the truck to confirm that I could find it and access it. I saw it and pulled the connector and then pushed it back on to confirm that that wouldn't be an issue either. Then I started my drive to Autozone. . .it was shifting fine! Almost there, it started "jerking" again going from 1st to 2nd. SO, I got the new VSS and installed it. . intermittent shifting issue still exists. In another forum someone suggested I "check the grounds". . .I'm starting to get in over my head. . I have NO idea where the "grounds" are or even what I'm looking for. . .any suggestions or alternative theories on why I'm getting the P0717 code and how to fix it? Thanks in advance! :)
 
That was a hard one until I remembered the 08s still had the 4 speed tranny
 

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I've attached some quick photo scans from the service manual as it pertains to the P0717 code.
 

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Thanks YGMN. . .I looked under "Problems: Systems" but didn't find much. . .then checked under "Problems: Basic Electrical" and found "2500 Ground Locations" with a pdf of a LIST of different systems and the ground locations but no pix, here https://www.chevyavalanchefanclub.com/cafcna/index.php?attachments/powerandgrounds-pdf.215431/. Maybe my next step is to post in the "Problems: Basic Electrical" forum. . .I'll do that and update this thread if I get anywhere. . thanks for everyone's help so far.
 
Hey MS03 and ca2kjet. . .thanks so much for that info. . .great stuff. . .I'll see if I can make anything of it and give it a go. . .thanks again and I'll update if and when I get any new info.
 
Check the wiring at the TCM, maybe even run a extra wire to ground from it.
 

Ground locations (Ref 2003)

Here is a start. LH Frame Rail at Body Mount (1) Ground 302 (G302) (2) LH Body Mount (3) Ground Screw (4) Electronic Brake Control Module (EBCM) (5) Fuel Tank Lower LF of the Radiator Support Components (1) LH Lower Radiator Support (2) Forward Lamp Harness (3) Negative Battery...
www.chevyavalanchefanclub.com www.chevyavalanchefanclub.com

not like they changed much.
 
Hey All! Update on the VSS/P0717 code. I knew it was over my head so I took it back to the shop that rebuilt my transmission 2 1/2 years ago (a line got corroded, leaked the tranny fluid and burned my transmission). They said that it was the INTERNAL speed sensor and the tranny needs to be dropped and disassembled to replace it. They're splitting the labor cost with me and doing the whole think including doing a once-over to see if anything else needs attention while they have it dropped. $750. I also let them know that I've seen tranny temps of 225 while pulling a small trailer in 90 degree heat, a buzzing sound with rpm, small clunk in drivetrain. I'll update when I get it back for hopefully a wrap up. Thanks so much for your help and fingers crossed I get another 100,000 miles out of this beast! (237k now).
 
nyjumpee said:
I also let them know that I've seen tranny temps of 225 while pulling a small trailer in 90 degree heat,
Click to expand...
Did the trans shop have any comments about 225 temps? I'm still curious what the 'best' fully heat-soaked temp is... In 90+ weather I'll see 205 with truck unloaded except passengers. I considered adding a cooler at one point but have also read these transmissions aren't 'up to temp' until 175-210.
 
Hey BainMan ~ They were supposed to start on this yesterday. . .I'll give them a call today and ask again about what they thought about the tranny temp. I believe they mentioned something about looking for blocked lines going to the existing cooler? Again, I'll ask again today and post the response. FYI I took it to a guy I know in Ohio that races at Nelson Ledges and owns a specialty mechanic shop and he said 225 is no big deal. . .but from what I've seen in the forums it's a bit on the high side. . cooler is better. . .
 
Hey guys late to the party as I just joined in. But I wanted to add some insights as I have had the 1-2 intermittent hard shift issue as well. I just bought the truck but the previous owner said that they just had the transmission rebuilt due to the hard shift. They said there was a broken part but didn’t know the exact name. I’m wondering if they were pulling my chain or not but I wanted to add in that even after a rebuild mine still from time to time will hard shift. Typically once maybe twice but after that it’s butter smooth. Reminds me of the shift kits in the early 350 trans. Maybe valve body related? Just some food for thought. Carry on
 
Hey Tonetacular ~ thanks for the input. I've had the exact same thought. . I've seen that the VSS (Vehicle Speed Sensor) tells the tranny when to shift. My issue was also intermittent. . .sometimes it would shift 1-2 smoothly as normal at around 1500 rpm. . .when it's NOT working, not only does it shift at a higher RPM at around 2500, BUT it also shift ROUGHLY. . .no smooth transition. . .again, I'm going to call them shortly and mention this as well. . .I'd hate to have the reassemble the thing and it's still shifting rough. . thanks for the input and I'll post any response. . .
 
You’re welcome bud! Mines doing the same thing even though it may be rebuilt. I know the guy the previous owner took it to so I could confirm with him. But I’m curious to hear what your shop has to say. Hope they get it figured out!
 
Hey Tonetacular ~ Hmmmm. . .weird that your tranny would still be doing it after a rebuild. . .I actually did speak with a mechanic yesterday and they haven't gotten a chance to start the job yet BUT he did say that rough/solid shifting is a part of the tranny going into "limp home mode" or something like that when it throws the P0717 code. . .which could mean that replacing the internal speed sensor would also clear up not only the higher rpm shifting from 1-2 but also the SOLID/JERKY shift as well. BUT he also said it's still possible that it may just be an external wiring issue e.g. bad ground, bad contact, loose wire, wiring harness, etc. on the EXTERNAL speed sensor which would save a lot of $$$. . .a wasn't aware that it wasn't a definite diagnosis until yesterday. Again, my issue in intermittent. .it shifted fine all the way to the tranny shop 45 minutes away. One weird note is that even on the days that it immediately started shifting rough, the VERY FIRST TIME it shifted from first to second after starting the vehicle was ALWAYS smooth. ..then rough every shift after that. . .weird. . .again, I'll keep updating as I get info and hopefully get this thing right ;-)
 
That’s what I thought when I bought the truck. Guy said the 1-2 shift was really hard sometimes so had it rebuilt. On the test drive it was smooth. Then when I brought it home it did it once. Thought maybe just cause it hadn’t been driven in a while.

Seems like a ground is always a likely culprit with any sensor. Usually I get afirm 1-2 shift within the first 10 min after that one it’s smooth and doesn’t do it again until the truck sits a couple days. (Work from home life) So who knows. Keep us posted I’m sure others will find all the info helpful ?
 
Okay. . BAD NEWS! It's been over a week for what I thought was going to be a day or so fix. . .just spoke to the mechanic. . .he said NOW THE TRUCK WON'T START!!! He dropped the tranny, put in the new speed sensor, reinstalled and since then, turn the ignition switch and NOTHING! There's power to the dash but the started WILL NOT ENGAGE. I've seen other Avalanches with this intermittent issue when turning the key, no starter, or hesitant starter. . .this may need a new thread. . .ANY IDEAS? This is really bumming me out now. . .he even dropped the tranny again, checked everything, checked grounds, starter, etc. . nothing. HELP :-(
 
SOLVED!!! The tranny shop called in an electronic specialist. . .apparently the BCM needed to be RESET. Now everything is back to normal! I asked them why, when they did the tranny 2 or 3 years ago that this didn't happen? "Sometimes it does, sometimes it doesn't". . .apparently this time the BCM stopped the truck from starting. . .they "reset" it and now it starts no problem. I'm picking up the truck tomorrow and I'll post again if I have any additional info. Thanks everyone for your help and input and hopefully someone can benefit from this experience :)
 
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