Lexus SC300 / Lexus SC400. Manual

TROUBLESHOOTING

How to proceed with troubleshooting
Perform troubleshooting in accordance with the procedure on the following pages.

CUSTOMER PROBLEM ANALYSIS

Using the customer problem analysis check sheet for reference, ask the customer in as much detail as
possible about the problem.

CHECK AND CLEAR THE DIAGNOSTIC TROUBLE CODES (PRECHECK)

If the ABS warning light lights up, and the ABS does not operate, the ECU stores diagnostic trouble codes
corresponding to the problem in memory.
Before confirming the trouble, 1st check the diagnostic trouble codes for any malfunction codes stored in
memory. When there are malfunction codes, make a note of them, then clear them and proceed to “

Prob-

lem Symptom Confirmation”.

PROBLEM

SYMPTOM

CONFIRMATION,

SYMPTOM SIMULATION

Confirm the problem symptoms. If the problem does not reoccur, simulate the problem by initially checking
the circuits indicted by the diagnostic trouble code in step

, using “Problem simulation method”.

DIAGNOSTIC TROUBLE CODE CHECK

Check the diagnostic trouble codes. If a malfunction code is output, proceed to “

Diagnostic Trouble

Code Chart”. If the normal code is output, proceed to “

Problem Symptoms Chart”. Be sure to proceed

to “

diagnostic Trouble Code Chart” after steps

and

are completed.

If troubleshooting is attempted only by following the malfunction code stored in the memory, errors could
be made in the diagnosis.

DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is confirmed in the diagnostic trouble code check, proceed to the inspection proce-
dure indicated by the matrix chart for each diagnostic trouble code.

PROBLEM

SYMPTOMS

CHART

If the normal code is confirmed in the diagnostic trouble code check, perform inspection in accordance with
the inspection order in the problem symptoms chart.

CIRCUIT

INSPECTION

Proceed with diagnosis of each circuit in accordance with the inspection order confirmed in

and

Determine whether the cause of the problem is in the sensor, actuators, wire harness and connectors or
the ECU.

SENSOR

CHECK

Use the ABS warning light to check if each of the signals from speed sensors are being input correctly to
the ECU. Instructions for this check are given in the circuit inspection.

[10] REPAIRS

After the cause of the problem is located, perform repairs by following the inspection and replacement pro-
cedures in this manual.

[11] CONFIRMATION TEST

After completing repairs, confirm not only that the malfunction is eliminated, but also conduct a test drive
to make sure the entire ABS system is operating correctly. (In vehicles with the TRAC system, also check
the TRAC system.)

BR–72

–

BRAKE SYSTEM

ANTI–LOCK BRAKE SYSTEM (ABS)