Where is the VSS located?

Tiny
DJ ART
  • MEMBER
  • 2007 CHEVROLET TRAILBLAZER
  • 4.2L
  • V6
  • 4WD
  • AUTOMATIC
  • 189,260 MILES
Can you please tell me where the vehicle speed sensor location is? I've replaced the 2 in the tail shaft of the transmission that thread into the location but apparently there's a 3rd that has a bolted hook connected to it but I cannot seem to find it. Also, I have replaced the 2 front ABS wheel sensors and no change. My vehicle will not shift at proper times and the speedometer will not work at all. I've searched numerous times but cannot find any information on it. Also, I have seen the posts online and all the pictures on here and they only point to the 2 sensors I have already changed.
Friday, March 18th, 2022 AT 10:23 AM

14 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,052 POSTS
Hi,

Take a look at the two pics I attached. There is an input and output sensor related to the transmission. There is also one in the rear of the transfer case.

I attached the pics below showing them. Let me know which ones were replaced. Also, let me know what diagnostic trouble code was found.

Let me know.

Take care,

Joe

See pics below.
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Friday, March 18th, 2022 AT 8:51 PM
Tiny
DJ ART
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Joe, thanks for the response. Okay, so pic #2 are the ones I replaced. I'm actually looking for #36 in the first pic, that's the one I haven't found to replace.
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Friday, March 18th, 2022 AT 10:33 PM
Tiny
JACOBANDNICKOLAS
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Hi,

That specific sensor is model-dependent. You may not have it on your transmission. If you do, it will be on the passenger side in the transmission tail housing. However, because this is a 4wd, chances are it isn't there.

Let me know. Also, do you have the specific codes that were stored?

Let me know.

Joe
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Saturday, March 19th, 2022 AT 6:14 PM
Tiny
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Yes, the code was a p0502 I believe andy obd2 reader said vehicle speed sensor.
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Saturday, March 19th, 2022 AT 10:17 PM
Tiny
DJ ART
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Joe, thanks for the response. Okay, so, pic #2 are the ones I replaced. I'm actually looking for #36 in the first pic, that's the one I haven't found to replace.
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Sunday, March 20th, 2022 AT 4:27 PM
Tiny
JACOBANDNICKOLAS
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Hi,

The two in picture two are on the transfer case tail housing. The one on the outside of the transmission (number 36 pic 1) is likely not there. It is likely for a 2wd vehicle. The only other one is internal, number 250. Is that the one you are referring to?

That is an input speed sensor located at the front pump on the transmission. See pic 1 below. Is that the one you didn't replace? Also, can you tell me what the code was you had that led you to the speed sensor?

Let me know.

Joe

See pic below.
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Sunday, March 20th, 2022 AT 8:13 PM
Tiny
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That is the only one I havent replaced. I was not aware there was an internal speed sensor. The code I received was the p0502 code which led me to the speed sensor.
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Monday, March 21st, 2022 AT 3:16 AM
Tiny
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Also, would that internal one cause the speedometer not to work?
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Monday, March 21st, 2022 AT 3:19 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,052 POSTS
Hi,

The input speed sensor works in conjunction with the output speed sensor to determine the speed and proper gear ratio. However, if the input one is bad, you will likely experience odd shifts, hard shifts, or codes specific to gear ratio issues. Other than the P0502, were there any other codes? Do the other gauges on the instrument panel work? Does the speedo do anything?

Also, the internal one shouldn't have an effect on the speedometer. That is the one at the rear of the transfer case that you already replaced.

I attached the diagnostics for a P0502, which is specific to an output speed sensor. Take a look through them and let me know if you are comfortable performing them.

Here is a link that you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

Let me know,

Joe

See pics below.

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Monday, March 21st, 2022 AT 6:34 PM
Tiny
DJ ART
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I will try all these tests, thank you for the amazingly detailed information. Also, can the TCM have any effect on the speedometer or sensors not responding? Reason I ask is because I talked to a shop that said the reprogramming with a new transmission should have been done and if it wasn't, the transmission was just "guessing" at what points to shift at until it stopped guessing. Is this a possibility as well?
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Monday, March 21st, 2022 AT 9:57 PM
Tiny
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Hi,

Programming should have been done, but if there was to be an issue, it would have happened right away. The TCM, which certainly plays a role in the issue, either knows something is right or wrong, and it would have indicated an issue. I don't see how it would finally get tired and stop working. Has anyone tried reprogramming?

Let me know what you find with the tests.

Take care,

Joe
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Tuesday, March 22nd, 2022 AT 5:57 PM
Tiny
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No, that's my next step in this whole fiasco. The guy I talked to has been in the industry for over 25 years, such as yourself, so I trust the advice I'm given and put it on my troubleshooting list. I haven't tried the testing as of yet since I need to get the time to do it from work and the vehicle is lowered so I need to get it on some ramps. I have everything written down and your illustrations printed to follow and appreciate everything you have provided.
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Tuesday, March 22nd, 2022 AT 6:23 PM
Tiny
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Also, pertaining to your previous question. No other codes were given other than the p0502. All of the other gauges work properly other than the ABS lights coming on now.
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Tuesday, March 22nd, 2022 AT 7:13 PM
Tiny
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Hi,

Sounds like a plan. The ABS light is the result of the other problem. They all tie together.

Let me know what you find or if you have other questions.

Take care,

Joe
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Tuesday, March 22nd, 2022 AT 7:59 PM

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