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.

Allison 3000 Series New World Automatic Transmission-troubleshooting a fault code

We recently had a no shift problem on one of our 2002 Thomas HDX pusher buses.

The code read on the pro-link was 45-12 which is an open circuit to the A solenoid. The A solenoid controls shifting into neutral which explains the no shift problem.

Since solenoids A, D, and J feed off the same voltage source we are probably looking at a low side or ground side wiring problem.


Disconnect the Deutsch bulkhead connector at the transmission and the T-connector or Blue connector at the ECU located under the removable cover on the right side of the dash.

Locate A and G circuits[trans. side] which is marked on the connector face. Run a jumper[Kent Moore #J39197] and check the corresponding wires at the ECU end, they will be T-1 and T-4. Using a digital multimeter [do not use analog meter!] check for opens, shorts and excessive resistance.

Check continuity and resistance to the A solenoid in the transmission itself. The control module[bottom side of trans.]houses the solenoids and hydraulic controls.

The result is resistance in the ECU to Bulkhead connector. So we will run a new shielded twisted pair of wires for the A solenoid circuit.



Replace wire ends for terminals T-1 and T-4 using Kent Moore J34182 Crimping tool. Once lock is remove from T-Connector The wires easily slide out of plastic locking tooth.







Lock newly installed wires into T-Connector at ECU and install
back into ECU with red plastic lock.








The Deutsch Bulkhead Connector unlocks and locks easily from transmission end when making repairs.









Use [Kent Moore J-38582] to remove wire ends from bulkhead connector.








Crimp new ends on replacement wiring using [Kent Moore J-38125-7] crimping tool.








Push in new wire end into bulkhead connector using [Kent Moore J-41194] insertion tool.

The code went away after this repair and the bus went back into operation. We have had a lot of success with wire replacement to fix transmission code problems since the wiring is exposed to the elements and tend to get damaged from the plastic convoluted loom that is used on most School Bus applications.

If the wiring would have checked out OK them we would have had to drop the Transmission Control Module and most probably would have had to replace the A Solenoid.

The tooling noted in this repair is required to do a proper job. Of course the cost of repair is diminished greatly when you can perform your own troubleshooting and repair. The WTEC 2 or WTEC 3 troubleshooting manual is essential with this kind of work.
The WTEC 2 ECU has two connectors while the WTEC 3 ECU has three connectors for easy identification of both systems.

WTEC=World Transmission Electronic Controls.