I drove my car this morning to the store and the stupid speedo says i am going like 110mph when i am really doing 35mph.... WTF.. Does anybody know what would cause this? I did just load a new program in my car and i had not drove it until today..... Could it be a bad pcm.... I have the pcm programed for the gears.. Could it be a ground?

 

something like that happened to me last year, except all the gauges were acting strange. My battery was dying after i took it out of storage in the spring, I replaced it and everything was back to normal.

 

My battery is brand new less than 2weeks old..... Thanks for the reply.... Just my speedo is going crazy the rest of the gages are fine..

 

Is yours and A4 or M6. The VSS for the A4 uses a much greater pulse rate than the M6 does. I found out what this does when I ran an old A4 tune in my purple car which now has an M6. Speedo went wild and shot up high.

Since you said you just got a new tune loaded, make sure that it was calibrated for the right transmission.

 

The VSS(vehicle speed sensor) is a 2 wire generator in the transmission. Basically a coil. These 2 wires from the coil go into the PCM. The PCM inturn ouputs the pulses to the instrument cluster and the cruise control module. The first thing to do is unplug the purtanent connectors at the PCM and look for bent pins. It should be the black connector and the red connector at the PCM. Reseat the connector.

If that doesn't help, try testing the cruise control if the speedo is still acting up. Then try reaseating all the other connectors at the tranny, at the instrument cluster, and C220 located in passenger kick panel. Look for the one with green/white wire.

If all that fails you will probably have to buzz out the wiring looking for poor connections.

 

The tune for the trans was unchanged we adjusted air/fuel .. The only thing that was diffrent was i replaced the connection on the ground that is on the pass. side block below the #6 plug .... Does gm require a certain ground? The weather was 15 degrees out ? I just don't know that is why i thought pcm?

 

So what happened when you tried the cruise control?

 

Update i checked all the grounds and they are all fine... Drove the car again and i have to rev it to 2300 rpm until the car will move and it still says i am going 100+ mph when i am still in first gear...

 

I would make absolutely sure that the computer tune was for your tranny.

 

The car ran fine before i loaded this last tune so if the pcm is fine i think i will load another program in and see what happens

 

I am having the exact same problem right now. Did a stall and Gear swap this weekend. Put the new program in and now my speedo reads way high. The shift points all seem to be right on, but the speedo reads like 100mph when I'm really doin like 75ish on the interstate... Also, as mentioned above, with the 3000 and 4.10 gears, I have to rev it up a bit to get going in first, and the speedo goes right up to 15mph when i'm barely moving.

My programmer guy is looking into it, and I'm going to climb under it tonight to make sure the VSS is plugged in correctly, but if it is, what else could it be?