General Information about ABS Testing

ABS_light_image1Trailer ABS systems contain an on-board computer with self-testing and diagnostic capabilities. During startup, when the auxiliary circuit is first powered, the ABS runs a self-check. The ABS status light comes on for 3 to 5 seconds, and you might hear the air valves “chuffing”. If the ABS status light fails to light up, blinks, or comes on and stays on, an ABS fault is indicated. Other systems self-test each time the stoplight circuit is powered (minus the chuffing).

Testing these systems is simply a matter of using your Square Wheel Industries Trailer Lighting Tester to power these two circuits and allowing the ABS to test itself.

Troubleshooting ABS

Many ABS systems have self-diagnosing abilities too, blinking out fault codes on the ABS status light, or illuminating LEDs on the controller. Each system has its own procedure, so you must know the correct procedure for the system you’re servicing.

Fault code reading and clearing from the 7-pole socket is beyond the scope of our equipment. Like it or not, we live in a time when you can’t even adjust the idle speed on many trucks without a laptop computer. Chances are, your shop has already gotten into electronics, and you may already have equipment capable of reading codes. In any case, the most cost-effective way to read fault codes is with the specialty equipment designed for that purpose. Furthermore, many code readers are designed to read any code- tractor or trailer ABS, engine management systems, even transmission codes. There are many sources for code readers, here are two:

Automotive Test Systems

Apex Tool

ABS technology is evolving rapidly; new systems and procedures are arriving almost daily. Even though testing and diagnosing ABS systems is a remarkably “user friendly” operation, the complexities of today’s vehicles make it essential that you know the correct testing protocol for the type of ABS you are servicing.

Express Garage and Express Mobile – Using the ABS Switch

The Express Garage and Express Mobile are equipped with full Scanner light testing equipment, but when the “ABS” switch is placed into the ”By Remote” position, control of the trailer’s auxiliary and stoplight circuits (the two circuits required to run the ABS self- test) is taken away from the Scanner and given over to your unit’s remote control. Then, when you press the remote’s red supply button, the unit powers up the trailer’s auxiliary circuit in addition to applying air pressure to the red gladhand. Likewise, when you hit the blue control button, the unit powers up the stoplight circuit.

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