Speed sensor problem, help

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Stokes1114

I'm Awesome
Joined
Apr 24, 2016
Messages
120
Reaction score
24
Location
Colorado
I have a 93 k1500 with 5.7, 4l60e. I just recently had the transmission rebuilt and it drove fine for 2 months after. A couple weeks ago my trans started shifting erratically and my park brake indicator comes on as well as the speedo goes crazy. It only does it about once a week, but makes it almost impossible to drive. I put in a new speed sensor and pigtail connector and thought it was fixed until today. I also tried another speed sensor buffer or drac but it continued to act up. I'm kinda lost as to what other wires I need to check. It does have a newly rebuilt posi rear end that I pulled from a 99 Yukon, not sure if this would have any effect
 

Fuzzy

I'm Awesome
Joined
Dec 26, 2013
Messages
135
Reaction score
21
Location
Illinois
Did you keep the same gear ratio with the rebuilt rear-end?
 

Fuzzy

I'm Awesome
Joined
Dec 26, 2013
Messages
135
Reaction score
21
Location
Illinois
The DRAC you put in was calibrated for a 3.73 Rear End I assume?

Also Code 72 is VSS Circuit Loss, so it might be easier to get a diagram and make sure you don't have any open circuits first.
 

Stokes1114

I'm Awesome
Joined
Apr 24, 2016
Messages
120
Reaction score
24
Location
Colorado
I didn't purchase a new drac for it yet, I pulled one from another truck but was unsure about the ratio so put the factory back in. I found a place online that will make one for the new rear end and larger tire size but was unsure if it was the problem
 

Stokes1114

I'm Awesome
Joined
Apr 24, 2016
Messages
120
Reaction score
24
Location
Colorado
The DRAC you put in was calibrated for a 3.73 Rear End I assume?

Also Code 72 is VSS Circuit Loss, so it might be easier to get a diagram and make sure you don't have any open circuits first.
The wiring is what throws me off bad. I'm not familiar with any wiring on these trucks, most of my knowledge is on older models
 

Fuzzy

I'm Awesome
Joined
Dec 26, 2013
Messages
135
Reaction score
21
Location
Illinois
It's basically an external device that processes the speed sensor signal (AC to DC) before it get's sent to the ECM, the best way to describe it would be as an equalizer of sorts I suppose.

The DRAC could cause the issues you're having and it definately would get a properly calibrated unit in the truck as soon as possible, However since you're getting a Code 72 I would look for an intermittent short somewhere in the DRAC wiring. I would start with the ground wire.

You must be registered for see images attach


Here's a wiring diagram, I believe this should be the one you need.

E: Also check the 15A Brake fuse for the Ignition Feed, if that's corroded it could cause intermittent voltage loss to the module.
 

Stokes1114

I'm Awesome
Joined
Apr 24, 2016
Messages
120
Reaction score
24
Location
Colorado
Awesome thanks for the diagram and help. The brake fuse is in the fuse panel inside the cab correct? Also the ground should be found on the engine or in the junction block?
 
Top