Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: How To Proceed With Troubleshooting

HINT:

• When troubleshooting, confirm that the problem symptoms have been accurately identified. Preconceptions should be discarded in order to make an accurate judgment. To clearly understand what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time the malfunction occurred.
• Gather as much information as possible for reference. Past problems that seem unrelated may also help in some cases.

• The following 5 items are important points for problem analysis:

  What	Vehicle model, system name
  When	Date, time, occurrence frequency
  Where	Road conditions
  Under what conditions?	Driving conditions, weather conditions
  How did it happen?	Problem symptoms

• The first function is the Diagnostic Trouble Code (DTC) check. A DTC is a code stored in the ECU memory whenever a malfunction in the signal circuits to the ECU occurs. In a DTC check, DTCs stored by a previous malfunction can be checked by a technician during troubleshooting.

• Another function is the Input Signal Check, which checks if the signals from various switches are sent to the ECU correctly.

  By using these functions, the problem areas can be narrowed down and troubleshooting can be more effective. Diagnostic functions are incorporated in the following systems of this vehicle.

  System	Symptom Confirmation and Diagnostic Trouble Code
  	DTC Check (Normal Mode)	DTC Check (Check Mode)	Sensor Check/Test Mode (Input Signal Check)	Data List	Active Test
  SFI System (2GR-FKS)	○	○	-	○	○
  Ignition System (2GR-FKS)	-	-	-	-	-
  Fuel System (2GR-FKS)	-	-	-	-	-
  Emission Control System (2GR-FKS)	-	-	-	-	-
  Intake System (2GR-FKS)	-	-	-	-	-
  Cooling Fan System (2GR-FKS)	-	-	-	-	-
  Starting System (2GR-FKS)	-	-	-	-	-
  Dynamic Radar Cruise Control System	○	-	-	○	○
  Front Camera System	○	-	-	○	○
  Lane Control System	○	-	-	○	○
  Road Sign Assist System	○	-	-	○	-
  Front Radar Sensor System	○	-	-	○	-
  Automatic Transaxle System (U881E)	○	○	-	○	○
  Automatic Transaxle System (U881F)	○	○	-	○	○
  Dynamic Torque Control AWD System	○	-	-	○	○
  Adaptive Variable Suspension System	○	-	○	○	○
  Tire Pressure Warning System	○	-	○	○	○
  Vehicle Stability Control System	○	-	○	○	○
  Electric Parking Brake System	○	-	-	○	○
  Power Steering System	○	-	-	○	-
  Power Tilt and Power Telescopic Steering Column System	○	-	-	○	○
  Steering Lock System	○	-	-	○	○
  Heated Steering Wheel System	-	-	-	-	-
  Audio and Visual System (for 8 Inch Display)	○	-	-	○	-
  Audio and Visual System (for 12.3 Inch Display)	○	-	-	○	-
  Navigation System	○	-	-	○	-
  Telematics System	○	-	-	○	-
  Intelligent Clearance Sonar System	○	-	-	○	○
  Intuitive Parking Assist System (w/ Intelligent Clearance Sonar System)	○	-	-	○	○
  Parking Assist Monitor System	○	-	-	○	-
  Blind Spot Monitor System	○	-	-	○	-
  Panoramic View Monitor System	○	-	-	○	-
  Garage Door Opener System	-	-	-	-	-
  Safety Connect System	○	-	-	○	○
  Lexus Enform System	○	-	-	-	-
  Charging System (2GR-FKS)	○	-	-	○	○
  LIN Communication System	○	-	-	○	-
  CAN Communication System	○	-	-	○	-
  Power Door Lock Control System	○	-	-	○	○
  Wireless Door Lock Control System	○	-	-	○	○
  Smart Access System with Push-button Start (for Entry Function)	○	-	-	○	○
  Smart Access System with Push-button Start (for Start Function)	○	-	-	○	○
  Immobiliser System	○	-	-	○	○
  Theft Deterrent System	-	-	-	○	○
  Lighting System (INT)	-	-	-	○	○
  Meter / Gauge System	○	-	-	○	○
  Headup Display System	○	-	-	○	○
  Airbag System	○	○	-	○	-
  Occupant Classification System	○	-	-	○	-
  Pre-Collision System	○	-	-	○	○
  Front Power Seat Control System (w/ Memory)	○	-	-	○	○
  Front Power Seat Control System (w/o Memory)	-	-	-	-	-
  Rear Power Seat Control System (for Second Row)	-	-	-	-	-
  Rear Power Seat Control System (for Third Row)	-	-	-	-	-
  Seat Heater System	○	-	-	○	-
  Climate Control Seat System	-	-	-	-	-
  Seat Belt Tension Reducer System	-	-	-	-	-
  Seat Belt Warning System	-	-	-	○	○
  Air Conditioning System	○	-	-	○	○
  Wireless Charging System	-	-	-	-	-
  Power Window Control System	○	-	-	○	○
  Window Defogger System	-	-	-	-	○
  Windshield Deicer System	-	-	-	-	○
  Sliding Roof System	○	-	-	○	○
  Panoramic Moon Roof System	○	-	-	○	○
  Back Door Closer System	○	-	-	○	-
  Power Back Door System	○	-	-	○	○
  Fuel Lid Opener System	-	-	-	-	-
  Power Mirror Control System (w/ Memory)	○	-	-	○	○
  Power Mirror Control System (w/o Memory)	○	-	-	-	○
  Wiper and Washer System	○	-	-	○	○
  Lighting System (w/ Automatic Headlight Beam Level Control System)	○	-	-	○	○
  Lighting System (w/o Automatic Headlight Beam Level Control System)	○	-	-	○	○
  Horn System	-	-	-	-	○
  Towing Converter System	-	-	-	-	-

• In the DTC check, it is very important to determine whether the problem indicated by the DTC either: 1) still occurs, or 2) occurred in the past but has returned to normal. In addition, the DTC should be compared to the problem symptom to see if they are related. For this reason, DTCs should be checked before and after confirmation of symptoms (i.e., whether or not problem symptoms exist) to determine current system conditions, as shown in the flowchart below.

• Never skip the DTC check. Failing to check for DTCs, depending on the case, may result in unnecessary troubleshooting for systems operating normally or lead to repairs not related to the problem. Follow the procedure listed in the flowchart in the correct order.

• The following flowchart shows how to proceed with troubleshooting using the DTC check. Directions from the flowchart will indicate how to proceed either to DTC troubleshooting or to the troubleshooting of each problem symptom.

NOTICE:

• Do not heat components to more than 60°C (140°F). Exceeding this temperature may damage the components.
• Do not apply heat directly to parts in an ECU.

NOTICE:

• Never sprinkle water directly into the engine compartment. Indirectly change the temperature and humidity by spraying water onto the front of the radiator.
• Never apply water directly onto the electronic components.

Electronic Circuit Inspection Procedure

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