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Speedometer fluctuating crazy Chevy Cavalier 01


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Amyeh
Novice

Oct 23, 2018, 3:12 PM

Post #1 of 8 (1324 views)
Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

Hi I'm new to this, I have a chevy cavalier 01- acting fine until one day the speedometer started acting erratic and bouncing between speeds even though I maintained the same speed. The check engine light, which quite honestly has always been on for a while is on, and just recently the trac off light is lit up. I do feel like the transmission was revving up as it switched gears or tried to. So initially I thought Sh!t! it's the transmission, so I took it to transmission shop, car too old to hook up to their diagnostic equipment so I thought maybe it was the VSS, had them put new one on for me. However, didn't fix it at all, went to my regular mechanic who said that could be a number of things, and that maybe it was the wiring harness leading to the speed sensor or the PCM needed to be reprogrammed at the dealership. The dealship said nope we don't think its the PCM, we think its the instrument cluster. Anyways I feel like i'm following a trail of bread crumbs, and these mechanics are saying we will diagnose it for you pay up, but we cant fix it, go try these guys... I'm lost, if anyone has had this happen to them with the speedometer, any advice would be helpful, I just need this to last until I've saved up for a new ride. Thanks!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 23, 2018, 3:46 PM

Post #2 of 8 (1284 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

Are you sure they changed the right speed sensor? There are 2 of them.

It's probably going to require a professional level scan tool to access the BCM and TCM data.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Amyeh
Novice

Oct 23, 2018, 3:58 PM

Post #3 of 8 (1279 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

Thanks for input. The transmission place- replaced the Output Speed Sensor. The other mechanics said it looked like it had been refurbished and possibly wasn't reading it, but idk. I notice it says recommend OE sensor is that a different one? Because they did do a scan on it and still couldn't give me a definite answer what is wrong with it. I have five variables, The vehicle speed sensor- is the refurbished one not working? the other speed sensor you just mentioned, the wire harness which they said looked like it was in poor condition, PCM, or the speedometer instrument cluster itself.

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Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 23, 2018, 4:03 PM

Post #4 of 8 (1273 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

That's not all the possibilities either. That signal goes through 3 computers and all that wiring.

If you are sure you got the output sensor, you got the right one. The input sensor has nothing to do with vehicle speed.

Simply reading codes is not what I meant. They are going to have to access both the TCM and BCM to see if they are receiving a sensor signal.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Amyeh
Novice

Oct 23, 2018, 4:14 PM

Post #5 of 8 (1269 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

But they did a reading on it and still couldn't determine what was wrong with it. My concern is with the refurbished VSS, they seemed to think that it wasn't reading it correctly. So now what... would one specific to the cavalier help? I just don't know what to do, I just paid to have them run diagnostics on it and it came up empty with some possibilities, I just can't believe no one seems to have encountered this before, why is it such a mystery.

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Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 23, 2018, 4:20 PM

Post #6 of 8 (1263 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

Diagnostics don't come up empty.

They may meet the limit of someone's ability but you just need a better technician. The problem can be found but you need a tech capable of doing that and one that possesses the proper equipment for doing it.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Amyeh
Novice

Oct 23, 2018, 4:45 PM

Post #7 of 8 (1255 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

Thank you for your advice, I appreciate it.

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Amyeh
Novice

Oct 23, 2018, 4:49 PM

Post #8 of 8 (1252 views)
Re: Speedometer fluctuating crazy Chevy Cavalier 01 Sign In

Thats a good point.






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