speedo q's on a 03 chevy

[dheavychevy38]

Ok on my gf's truck she has a 03 silverado extcab 4x4 with a 5.3. Heres the problem sometime when driveing and you go to slow down the speedo will drop then when u continue driveing at any speed it is way off say like 15 will be 60 or doin 30 and the speedo reads 85 90 not a good thing. Any ideas thanks denny

 

[dyeager535]

Something that new I'd suspect the speedometer (/speedo wiring) or VSS, but I'd want to see what the ECM was seeing while the speedometer was acting up.

If it were the VSS, I'd imagine the SES light would eventually come on, and/or other symptoms such as weird shifting, idle, and anything else using the VSS signal as an input.

I've got no hands on experience with things this new, but with vehicle speed playing such an important role in the EFI vehicles, the above would seem to be a decent guess.

 

[dheavychevy38]

the vehicle doesnt run any different when it happens.

 

[dyeager535]

Sorry man, not much more idea than that, but since shifting is partially tied into vehicle speed, and you aren't noticing any shifting issues, I'd *suspect* a speedometer/wiring issue.

Hopefully someone that has more experience on these trucks has an answer. Exhibiting symptoms when that new, it may be a fairly common issue.

 

[dheavychevy38]

ya its only once in a great while last time it did it was 4 months ago thats how random it is its not like i can do somethin a certain way and get it to act up. Thats the bad part.

 

[obijuan]

my dads 03 just quit working completely, whatever happened to the good ol mechanical speedometer cable?