How To Troubleshoot Air Brake System ABS Code .

This ABS system is by Meritor Wabco found on most highway transport vehicles. An ABS light on the dash indicates a problem that has to be repaired since an ABS fault is a fail according to Motor Vehicle Inspection criteria. The ABS system does not operate normally when there is an active code.

The code description reads "Right Front Wheel Sensor - Open"

When looking at the Right Front wheel the sensor looks like it's intact. The first thing to check is to make sure the sensor is pushed all the way into the housing. The sensor reads a tone wheel on the hub and sends a signal to the ABS Control Module.

According to the troubleshooting specs the resistance of the sensor should be between 900 and 2000 ohms. When I checked it out there was no continuity causing an obvious open circuit as indicated by the fault description. The first step is to check the wiring itself for any damage or the possibility of a faulty sensor. Most times exposed wiring to the environment is at fault when troubleshooting a circuit problem.

Further inspection shows a spot on the sensor wiring that has rubbed through on the brake pot assembly. One of 2 wires has been damaged and caused the open circuit condition. I use heat shrink butt splices since they seal very nicely from the environment.

Once the sensor was replaced I moved the bus in a forward direction & the ABS warning light went out. This was an easy fix and it was nice to stumble across the bad wire in an easy to reach location. This conventional school bus is a only a year old but you never know what can happen to wiring and components when operating on a daily basis. I hope this mechanic information has helped you out and maybe you will have it as easy as I did with repairing this failure.

Replacing Kingpins International Thomas School Bus

I recently had to replace the Kingpins and Bushings on a 2000 International Thomas School Bus. The bushings were showing movement on the Drivers side. During disassembly I had seized taper lock pins in the axle bore. These taper pins secure the kingpin itself to the axle bore.

The trick is to drill out each pin with a 3/16 drill bit [cobalt if you have one] and heat up the hole with a torch. Once the pin is good and hot [orange range] hit it with water and cool it down. This shrinks the pin and out it comes with a good rap with hammer and punch. You'll find this works 99% of the time.

The lower pin has a threaded end. This is an option since the new kingpin kit comes with extra taper pins without the threads. The pins go in the opposite direction. The upper pin seen here points towards the rear of the bus, the lower pin faces the front.






A cobalt drill bit goes through the pin material like butter. I'm not sure what kind of material the pins are made of but they're solid!







Once the cool down contraction has taken place the pins will knock out of the axle very nicely! I wouldn't recommend using this method on something like an engine block[removing a seized plug etc.], very sensitive to dry heat and there's no telling what could happen.






Removing the ABS wheel sensor is easy, The sensor slides out of the steel sleeve in the spindle. Make sure to seat it completely before reassembly[you'll get an ABS code]

This is a tidbit of Mechanic Information that I hope will help you out someday!