Speed Sensor Failing?

[bigburban383]

When the speed sensor goes bad on a 90' Burban, does the speedometer needle just jump around sporadically? I looked under and followed the wires and connectors, they look okay. It sucks because my ABS is outta wack too and braking is a trip.

 

[big83chevy4x4]

pull the sensor and check the reluctor ring and the sensor.

on my s10, my speedo was possesed. when you step on the gas, the needle went slower. the faster i was going the slower it said i was going when on the gas. when i let off the gas, the needle would show about the correct speed. at 70mph when i had the petal to the floor it showed 10mph and when i let off it was about 70. Thats the fastest the speedo ever moved /forums/images/graemlins/whistling.gif turns out when the tranny blew up 2 weeeks later(t5) the reluctor ring was ground down from metal shavings on the sensor. put a new reluctor ring in the new tranny and it worked perfect.

 

[dyeager535]

From my understanding of that DRAC setup, you should be able to watch the ECM (need a scanner) and see what the speed sensor says the vehicle is doing.

With ABS issues it would seem to be more likely the VSS, as I doubt the ABS stuff works off of the speedometer. I'd still hook a scanner up and see what the ECM sees for MPH as you drive.

 

[realsquash]

IIRC that speedo is still mechanical and the electronics use a sensor up in the dash or under the hood on the speedo cable.

Andy

 

[big83chevy4x4]

90 was the first year for electric speedo.

 

[bigburban383]

Scanner, very good idea /forums/images/graemlins/waytogo.gif