Lexus ABS Diagnosis Technical Training PDF Manual Guide

Diagnosis and Troubleshoting The ABS ECU has a self-diagnostic system which monitors the input and output circuits. The ABS ECU operates the solenoid valves and the pump motor in sequence in order to check each respective electrical system. This function operates only once each time the ignition switch is turned ON. On some earlier models it operates when the vehicle is traveling at a speed greater than 4 mph with the stop light (brake light) switch OFF. During this check the operation of the actuator can be heard, however this is normal and does not indicate a malfunction.

Diagnostic Function When a problem is detected in any of the signal systems, the ECU turns on the ABS warning light in the combination meter to alert the driver that a malfunction has occurred. The code is stored in memory for access at a later time. Diagnostic trouble codes can be read from the Warning light. The ABS ECU will also store the diagnostic trouble codes for any ABS malfunction.

Trouble Code Check To access the diagnostic trouble codes stored in the ECU, locate the Data Link Connector (DLC1) or (DLC2). Consult the Repair Manual or the ABS Reference Card to determine whether the ABS Check Connector is physically disconnected or the short pin for Wa and Wb is removed. To access diagnostic codes o Disconnect the check connector or remove the short pin in DLC1. o Jumper terminals Tc and E1 of the Data Link Connector (DLC1 or DLC2). o Turn the ignition switch ON and read the trouble code from the ABS warning light on the Combination Meter.

Diagnostic Codes If the computer has not detected a malfunction, the lamp will blink two times per second after a two second pause. When a malfunction has been detected there will be a 4 second pause, then the first digit will begin. The number of times the lamp blinks before a one and a half second pause is the first digit of the code. Next, the number of blinks before the second pause is the second digit of the code. In the example below, the first code is Code 11 and the second code is 21. If there is more than one trouble code, the code with the smallest number will appear first, followed by a pause for 2.5 seconds

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