I have a '91 305 tbi camaro, I have been having problems with my speedometer. It will work every so often on the highway going like 50 but for the most part is dead. I have changed the gauge cluster with another one from a 91 and i have changed the VSS but still am getting the same problem. I have checked continuity and all seems well.

Is there any other part that could have gone bad? I am at a lose and really don't want to go out and buy aftermarket gauges just so i can have a speedometer.

Any help would be appreciated.

P.S. The stock 2.73 rear gears were swaped to 3.73 in case that would have any effect other then the speedomter being off.

 

The plastic gears may be worn or stripped. One or both.

 

I checked them when i changed my VSS they seemed fine......I found the vss buffer and was testing that out. I can get a signal from the VSS but i can't get a signal out of the buffer, i'm not sure which wire should have the signal since the haynes and chilton manuals are basically useless on that since they only have cable driven speedo info......

Does anyone know where i can get wiring diagrams for electric speedometers?

 

Hope this helps any


If Not, then see this and scroll almost clear down to the bottom and that might help some more

VSS Wiring

 

Ooops, double post

 

If i'm correct the vss sends out a 4000 ppm signal and from your diagram the speedo takes in a 4000 ppm signal.
If this is true is there a way to bypass the buffer inorder to see if that is bad?

My cruise control doesn't work either and it would be great to see this fix it.

Does anyone know where to buy one? I can't find it anywhere..

 

I don't know of a way to bypass the buffer to see if it is bad....

To be honest with ya, there isn't much inside the buffer module to make it fail...
Odds are, if you are getting a signal into the buffer, but not outta, then it is bad...
On the other hand, from reading about the Camaro speedo, the signal comes from the ECM, not directly from the buffer like the Firebirds...

 

I haven't heard of too many buffers failing but if the cruise isn't working I would look at it as a possibility. Do you have access to a scan tool? Most scan tools have a setting that shows vehicle speed, this would help rule out the speed sensor. Camaros and Firebirds both use the buffer, The later TPI cars don't have one

 

you might want to check your speedometer cable just to make sure it is not loose or you may need to replace it.

 

I swapped out the buffer for a friends and still got nothing...........
could anyone point me in the direction of a good wire diagram because it looks like alot of wire tracing for the next few days.

I wish I had access to a scan tool.....

 

check the ground and voltage at the buffer and check continuity between pin C on the buffer and the instrument cluster. pin a & b go to the vss. Pin F goes to the ecm pin A10. Once you establish no broken wires, the only thing left is parts. You tried the cluster, and the buffer

Installing an electric speedometer in your Firebird this website is for converting to an electric speedo, but it explains some of the wiring

https://www.thirdgen.org/unlimited this one explains more on the wiring, but shows a TPI speedo circuit without the buffer.

AutoXray has a speedo function, and so does winaldl

 

Between all the diagrams that were provided (btw thanks alot guys)
I checked all the wires from the vss to the buffer, each buffer out going wire to the ecm and speedo and all have continuity. I can't find any diagrams on camaro gauge cluster wiring. Does anyone know where to get them from?

I have also swapped out the new vss, buffer and cluster and nothing changed.

If anybody as any sugestions i would greatly apreciate the help, I really don't want to goto aftermarket gauges just to get a working speedo but that time is slowly becoming inevitable.

 

I found this post for you, it lists a vss gound and speed sensor on the cluster. It was posted by Trickster, you might want to contact him. https://www.thirdgen.org/forums/atta...f?d=1085178375