Lexus SC300 / Lexus SC400. Service manual

HOW TO PROCEED WITH TROUBLESHOOTING

Perform troubleshooting in accordance with the procedure on the following page.

[1]

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet for reference, ask the customer in as much detail as
possible about the problem. A subjective complaint such as ”poor air conditioner efficiency” is also consid-
ered in the air conditioner complaints.
Therefore, in ”Customer Problem Analysis” and ”Problem Symptom Confirmation”, check carefully to deter-
mine whether the level of performance is the actual (normal) level or whether it is abnormal. Then perform
troubleshoot accordingly.

[2]

CHECK AND CLEAR THE DIAGNOSTIC CODES (PRECHECK)
First check the diagnostic codes to see if there are any malfunction codes stored in memory. If there are
malfunction codes, make a note of them, then clear them and proceed to [3] problem Symptom Confirma-
tion”.

[3]

PROBLEM SYMPTOM CONFIRMATION, [4] SYMPTOM SIMULATION
Confirm the problem symptoms. If the problem does not reappear, be sure to simulate the problem by main-
ly checking the circuits indicated by the diagnostic code in step [2], using ”Problem Simulation Method”.

[5]

DIAGNOSTIC CODE CHECK
Check the diagnostic codes. Check for problems with the sensors or the wire harness.

[6]

DIAGNOSTIC CODE CHART
If a malfunction code is confirmed in the diagnostic code check, proceed to the check procedure indicated
by the matrix chart for each diagnostic code.

[7]

MATRIX CHART OF PROBLEM SYMPTOMS
If the normal code is confirmed in the diagnostic code check, perform inspection in accordance with the
inspection order in the matrix chart of problem symptoms.

[8]

CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection order cofirmed in [6] and [7]. Deter-
mine whether the cause of the problem is in the sensor, actuators, wire harness and connectors, or the
ECU.

[9]

ACTUATOR CHECK
Check actuators for proper operation. Instructions for this diagnosis are given in the flow chart for each
circuit.

[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 perform diagnostic
code check and actuator check, etc. again to make sure the entire air conditioning system is operating cor-
rectly.

AC–22

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AIR CONDITIONING SYSTEM

REPAIR INSTRUCTIONS