Friday I noticed my speedo jumping while in drive with my foot on the brake. Soon thereafter my ABS and Brake lights came on. I didn't get any codes when I hooked up the tuner and checked. The lights went off when I restarted the truck but came back on after sitting at a light.
I replaced the speed sensor on the rear diff and that seemed to work for a while. I am still noticing my speedo jumping although the ABS and Brake lights aren't on.
Are there any other sensors I need to check?

² Vehicle Speed Message - Each time the cluster
receives a vehicle speed message from the PCM it
will calculate the correct vehicle speed reading and
position the gauge needle at that relative speed position
on the gauge scale. The cluster will receive a
new vehicle speed message and reposition the gauge
pointer accordingly about every 88 milliseconds. The
gauge needle will continue to be positioned at the
actual vehicle speed position on the gauge scale until
the ignition switch is turned to the Off position.
² Communication Error - If the cluster fails to
receive a speedometer message, it will hold the gauge
needle at the last indication for about three seconds,
or until the ignition switch is turned to the Off position,
whichever occurs first. After three seconds, the
gauge needle will return to the left end of the gauge
scale.
² Actuator Test - Each time the cluster is put
through the actuator test, the speedometer needle
will be swept to several calibration points on the
gauge scale in a prescribed sequence in order to confirm
the functionality of the gauge and the cluster
control circuitry.
The PCM continually monitors the vehicle speed
sensor to determine the vehicle road speed. The PCM
then sends the proper vehicle speed messages to the
instrument cluster. For further diagnosis of the
speedometer or the instrument cluster circuitry that
controls the gauge, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING).
For proper diagnosis of the vehicle speed
sensor, the PCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the speedometer, a DRBIIIt scan tool is required.
Refer to the appropriate diagnostic information.

This is from the '03 manual.

JG

Thanks for the info.

Having the same problem with mine right now!

things I,ve done so far

reset PCM
disconnected the battery for 2 hrs
scanned for codes with SC no codes.

If anyone has any ideas before I take it to the dealer please let me know.

Danny, take it in if you are still under warranty...

quote:

Originally posted by rdsetgo:
Danny, take it in if you are still under warranty...

Thanks Rob. Im going to the dealer first thing in the morning. Im 3,ooo miles out of warranty

What about the 7/70??? If it is not in the PCM side you might still have going for you!!

well turns out my PCM needed an update/flash. everything checked out ok. Ran into VA4MEDS there. reason for the update was the programer/tuner deleted the tire config.

So how much did tha set you back???

$88.00 which i dont think it was too bad! I was expecting 100. plus

Not too bad what tunner do you have????

Lets just say it was not my Superchips. I cant say right now but I will let you know soon.

Glad to know that it was not the SuperChips that had me worried!!

I was trying out a new tuner but It didnt work for me.Right back to Superchips and happy with that.I did pay the price as mentioned before for trying something diff.

Can you pm the name of that other tunner???