I have an 04 4x4 Sierra crew cab. My speedometer just started bouncing a couple of weeks ago. Replaced the transmission speed sensor and no change. Any ideas?
Bouncing speedometer
- Thread starter sweettsinger
- Start date
Mooseman
Moderator
Me again! My mechanic says it's the transmission speed sensors but I'm not so sure. I bought the truck about a year ago and have had to replace a lot of things. I noticed a rumbling sound about 6 months ago but could not figure out the problem. Come to find out the transfer case had leaked all the fluid out. Anyway, I bought a used one and my mechanic put it in last week. Now my speedometer doesn't work at all and my odometer isn't working either! Plus my transmission doesn't shift from 3rd to drive! Any thoughts?? PS. I have new speed sensors to put in this week!
Mooseman
Moderator
Would strongly suggest following up on @Mooseman's advice re: the ELM327 and Torque. A link to a discussion thread with details on a proven ELM327 unit is attached below:
https://gmtnation.com/forums/threads/elm327-class-2-serial-data.21262/post-649639
Cost of the dongle & Torque app will be in the range of $25-$35; money well spent as it will enable you to do some investigations on your own to better ensure you get to the proper diagnosis..
Lots of help here on this forum if you have any questions.
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And for an "In-Depth" Professional Shop's VSS Diagnostic, courtesy the Snap-On Vantage-Pro Lab-Scope, Graphing Dual Multi-Meter and Component Testing Procedures approach... have a look at these images for some additional functional information and Testing Regimen to follow.
Mind you, some of them are "rendered just a little bit akimbo..." because I had the Vantage Pro in my lap when I was using the digital camera to capture the Screens that are SPECIFIC to your 2004 GMC Sierra Crew-Cab. These should work across a wide range of Engine Displacements since the VSS for the 4L60E and 4L65E Transmissions are identical in form and function:
More Images to Follow on...
Mind you, some of them are "rendered just a little bit akimbo..." because I had the Vantage Pro in my lap when I was using the digital camera to capture the Screens that are SPECIFIC to your 2004 GMC Sierra Crew-Cab. These should work across a wide range of Engine Displacements since the VSS for the 4L60E and 4L65E Transmissions are identical in form and function:
More Images to Follow on...
I'm not a mechanic and I don't understand what these images are telling me. Still can't figure out why the transmission isn't shifting right!?
Mooseman
Moderator
No. It`s a passive module, only displaying the data that is fed to it by other modules. The only thing it could do is take down the whole network if it`s totally borked and shorting the network. There would be a whole lot more wrong with the truck if that happened.
If the tranny doesn`t shift right AND the speedo is bouncing, I would suspect more an issue with the speed sensor or its wiring.
Before you back up the parts canon and start firing away you (or someone else) is going to have to look at the speed sensor *data* while driving. You want to determine if the *data* reflects what the vehicle is actually experiencing (i.e. do any data spikes correspond to engine or vehicle speed spikes). An ELM327 dongle and an app like Torque Pro can easily handle this.