Transmission is not shifting properly, erratic tachometer, speedometer, no indicator shift light

IVAN AZCUE

MEMBER
1995 CHEVROLET 2500
5.7L
V8
2WD
AUTOMATIC
150,000 MILES

My vehicle isn't shifting correctly, erratic speedometer, erratic tac checked fuses. Fuse 20 inside vehicle is a 10amp fuse but isn't getting power.
Looks to be going to transmission. Replaced VSS on transmission but no change.

4 Replies

KASEKENNY

MECHANIC
18,907 POSTS

You are correct that this is normally a vehicle speed sensor so I went ahead and attached that info below as others in the future may have this issue and they need to start with that just like you did.

However, if you changed it and it still is acting up then we need to do a couple things.

First and foremost, we need to check for codes. While I don't expect any we may be pleasantly surprised.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes then we need to investigate this fuse further.

I attached the wiring diagrams below as well and they show that this fuse is a 20A fuse. So when you say you have no power, do you have power on the front side of it and not on the other or no power on either side?

If you have it on one side then the fuse is blown. If you don't have it on either side then we have an issue on the fuse panel circuit board. However, that will cause a shifting issue as this fuse powers the shift solenoids.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Please run through this material and let us know if this is in fact the case. If it is then maybe we jump 12 volts to this circuit and see if all issues are resolved. Then we can just figure out why you don't have voltage there as we know that will solve the issues.

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Saturday, September 4th, 2021 AT 3:48 PM

IVAN AZCUE

MEMBER
25 POSTS

So I took your advice and checked the fuse put a 20 amp fuse s even though the panel says it should be a 10:00 amp fuse. And I got power. I believe my 10 amp fuse looked good but was bad.

The park neutral indicator light light came on. It shifted into reverse and into drive I could feel the shift. I took it for a drive shifted fine until the orange indicator light faded out it was causing the speedometer and tachometer to act erratically. It eventually came back on as I was driving and speedometer worked and tac until it faded out again.

I figure I have some kind of resistance in that pink wire.

I followed the wire to the bottom I could not find it I included 2 pictures the 2nd picture I believe is the vehicle speed sensor with all those wires there's not really sure.

I see several pink wires.

Where do I go from here?

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Monday, September 6th, 2021 AT 10:31 AM

IVAN AZCUE

MEMBER
25 POSTS

82, 83, 87, 12 68, 81 obd codes.
I looked most of those up and and they all relate to the transmission not getting power.

I included a short video of the indicator light fading in-and-out

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Monday, September 6th, 2021 AT 11:35 AM

KASEKENNY

MECHANIC
18,907 POSTS

Yep. I think you are on it. I suspect we have a wiring issue as that would make the most sense with all these codes.

I included the list of these codes below but I would suggest just picking one and run through the testing to find out where that takes us.

I attached the testing for 82 as I suspect we will find something with this testing.

Let me know what questions you have. Thanks

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