Speedo doesn’t work till 20 mph and abs goes crazy need help

[Vortex56]

After replacing my abs wheel speed sensor my Speedo doesn’t work till I get to 20 mph and when braking the abs goes crazy

 

[pjtoledo]

which wheel? or is it the rear axle?
first guess is the new sensor is weak or not close enough to the trigger wheel.
dirt/rust preventing it from seating properly.

 

[Vortex56]

It is the rear axle and it is the sensor on the diff and what would be the best way to get it to seat properly also how would I check if the sensor is weak

 

[pjtoledo]

scrape rust from around the hole. plug the hole first to keep debris out.
spray something into the connector, reset it several times to get thru any corrosion on the pins.

I have an Oscilloscope so checking output is easy for me. try AC millivolts on a digital meter.

the signal will increase in amplitude proportional to rotational speed. when you hit 20 the signal has increased enough to work.
the signal will decrease as the gap to the trigger teeth increases, so fully seating into the hole is needed.

what did the old sensor do?

 

[Vortex56]

I have had weird Abs issues when braking an audible click is heard and the brake pedal would go down and come back up and keep clicking and doing that until the pedal was released I I figured I would try the Abs sensor

 

[Vortex56]

scrape rust from around the hole. plug the hole first to keep debris out.
spray something into the connector, reset it several times to get thru any corrosion on the pins.

I have an Oscilloscope so checking output is easy for me. try AC millivolts on a digital meter.

the signal will increase in amplitude proportional to rotational speed. when you hit 20 the signal has increased enough to work.
the signal will decrease as the gap to the trigger teeth increases, so fully seating into the hole is needed.

what did the old sensor do?

I got it fixed it wasn’t seating properly and also replacing the sensor fixed my weird ABS issue so thank you for all your help

 

[Tommy2u]

Hi, can anyone tell me where the speed sensor is on my 1999 Ranger 3.0 Auto 2 wheel drive? I can't find any sensor on the transmission's left rear top. So I changed the ABS sensor on the rear end and the speedometer still isn't working. I don't know what next, I appreciate any info yall might have.

 

[Vortex56]

The abs wheel speed sensor is located on top of the diff and make sure it is seated properly that is what fixed mine

 

[pjtoledo]

the system needs a good sensor, and good wires back to the ABS module.