ABS 5.3 Antilock Brake System for Early Subaru Part 5:

ABS 5.3 On-Board Diagnostics

Using on board-diagnostics is very similar to the ABS-2E system. Three trouble codes are the limit of memory retention with the newest code being displayed first. Accessing of trouble codes is achieved by first turning off the ignition switch, then grounding terminal 3 of the 6 pole service connector B82 located above the accelerator pedal, then turning on the ignition switch. The codes can be viewed on the ABS warning light. The trouble codes for the ABS 5.3 system are the same as the 2E system with the addition of trouble code 29. This code will be generated when the speed of one of the wheels is 1.25 times faster than the others for at least one minute.

ABS 5.3 Sequence Control

Sequence control is also activated by the use of the six pole service connector B82. Ground terminals 3 and 6, turn on the ignition and apply the brake, as described in the service manual, within .5 seconds after the warning light has turned off. The left front wheel and the right rear wheel, while in sequence control, are activated together. First pressure drop will occur (the service manual describes the procedure for connecting the pressure gauge). Observe and record the pressure drop. Pressure hold will then be activated followed by Pressure Increase Mode.

In each case observe and record the pressure readings. Compare your results with the specifications in the service manual. The operation of the right front and left rear sequence control immediately follows the left front and right rear. So if you do not have four pressure gauges you must enter Sequence Control enough times to check the operation of each wheel.

Clearing past trouble codes is accomplished by entering D-Check and then grounding terminal 6 of B82, three times within 12 seconds, with the ground pulse lasting at least .05 seconds. All AWD 5.3 vehicles use a G-sensor. The G-sensor for the ABS 5.3 system is a capacitance type and its input to the electronic control unit modifies the computed average vehicle speed. This sensor varies its output with changes of G-forces by changing the capacitance of an internally located capacitor. The G-sensor is located under the center console just behind the hand brake lever.

A word of caution: Do not confuse ABS/TCS with ABS when choosing the correct pathway for communications with the ABS 5.3 system.