Hello everyone. I'm new here and i'm hopeing someone can help me solve a brake problem.

On my lariet i'm told the reason my brake is fading to the floor is because my front right speed sensor is not working. Constantly showing 3mph.

Has a new master cylinder and the system has been bled 3 times. Last two times by the shop. Any ideas of how to fix this problem? The shop is scaring me with a possable 1000-1400 dollar repair bill.

 

Sounds pretty unlikely for a sensor to cause that.

Are you certain you have 4WABS on a 97? It was an option and was not very common.

 

the shop took me for a ride and he was plugged into the orbll.
it showed the right front speed at 3mph from dead stop to rolling. at the time the others were showing 17mph. Just the one at 3mph.

Im also trying to figure what goes with the speed sensor. I see there is a sensor ring on the hub, but what else? seems to me there should be a gear looking thing that it detects the speed from. dont know what it is called.

also, would the speed sensor cause my bad brake pedal???

 

The sensor will not cause the pedal problem - that's a hydraulic issue. It might be the 4WABS module telling the EHCU to open the dump valve due to faulty interpetation of the wheel sensor data or it might be a stuck or leaking dump valve in the EHCU that is bypassing your pressure. You really need someone who understands this electro-hydraulic system to look at it so you don't waste more money. The factory service manual has specific checks to be made by the technician to help identify the fault.

The front wheel sensors use a magnetic pickup. The sensor is mounted in the hub/spindle and is positioned next to the ring on the hub. As the wheel/hub/sensor ring rotates, the sensors generate an AC voltage whose frequency is proportional to the speed of the wheel. It's up to the 4WABS module to translate this variable frequency signal into the equivalent value of MPH.

A static resistance check of the wheel sensor can check for shorts, opens, and whether the sensor exhibits the correct resistance. On the 2WD version of the 97 4WABS, the sensor should read around 4K ohms resistance, according to the manual. If you were to connect your meter to the output of the sensor and would spin the wheel, you should see a small (1-5) volt AC signal.

However, I doubt the sensor itself is causing the indication. It's more likely the 4WABS module. Your shop will need to do some more diagnostic work to see what the real problem is.