Scan Tool Testing: Overview

DIAGNOSTIC COMMAND MODES
The ABS system includes several self-tests that are performed every time the ignition is turned on and the vehicle is driven away. Some of the self tests occur immediately, while others do not occur until the vehicle reaches a certain speed.

SELF-TEST AT IGNITION TURN ON

RAM AND ROM CHECKS
RAM and ROM are the two major parts of the microprocessor in the EBC 2 and EBC 325 CAB. The RAM and ROM are checked immediately whenever the vehicle ignition is turned on.

BULB CHECKS
At ignition turn-on, the CAB also provides the operator of the vehicle with a visual check of the amber ABS warning indicator and the red BRAKE warning indicator. When the ignition switch is turned to the RUN position, the two indicators are turned on for a few seconds. These bulb checks help confirm correct operation of both the CAB and the bulbs themselves. In addition to the visual checks, both indicators are checked by the CAB for circuit failures at this time (as well as at any other time that the indicators are lit by the EBC 2 or EBC 325 CAB).

SELF-TEST AT INITIAL IGNITION ON
The system undergoes a power-up self-test when the vehicle has it's initial ignition turn-on. An active self-test of the ABS system internal main relay, motor, and the six solenoid valves is performed. The power-up self-tests are abbreviated if the vehicle ignition switch is turned from some other position to RUN, as might occur in restarting a stalled engine with the vehicle rolling.

DRBIII DIAGNOSTIC COMMANDS

RESET MODULE
This command resets the EBC 2 and EBC 325 system as follows: it turns off both warning indicators, clears all trouble indicators and counters in the NVRAM, and reactivates the system. The reset module command is accepted by the CAB only if the vehicle's wheels are not rotating.