How to Read and Clear Fault Codes on a Lexus

If you’re facing challenges with your Lexus and need to get to the root of the issue, our guide is here to help. It’s designed to teach you how to read and clear fault codes from all the key systems in your Lexus. Whether it’s the Engine Control Unit (ECU), Transmission Control Module (TCM), Anti-lock Braking System (ABS), or Vehicle Stability Control (VSC), this guide empowers you to identify and resolve problems efficiently. By mastering these steps, you’ll ensure that your Lexus continues to deliver the exceptional performance and reliability it’s known for.

Your Lexus is a marvel of luxury and modern engineering; however, like any complex system, it’s susceptible to occasional glitches or malfunctions. If you see a Check Engine Light (CEL), that could mean your transmission or any other warning light like SRS, ABS, traction control, or differential. That’s where Diagnostic Trouble Codes (DTCs), also known as fault codes, come into place.

Procedure of Reading and Clearing DTCs or Fault Codes

1. Gather the necessary tools: Equip yourself with a Professional-Grade OBD-II Scanner compatible with your Lexus. Click Here for our Professional-Grade YOUCANIC Scanner
2. Access the OBD-II Port: This port is usually found under the dashboard, near the steering column; the OBD-II port is the gateway to your car’s diagnostic information. Turn the ignition key to the “ON” position without starting the engine to make a connection with the vehicle’s computer. If your Lexus has a START/STOP feature, press the button without pressing the brake pedal. Do not start the engine. If you are unsure of the OBD-II port of your vehicle, you can always check the Car Owner’s Manual.
3. Turn on the ignition, but do not start the engine. All dash lights should turn on.
4. Access the Diagnostic Menu: On the YOUCANIC scanner’s display, navigate to the “Diagnostic” or “Scan” menu. This menu allows you to access various diagnostic functions for your Lexus.
5. Select ‘LEXUS’ as the Vehicle Make: This ensures the scanner effectively communicates with the Chrysler On-Board Diagnostic system and effectively scans the fault codes.
6. Select option for model selection: The scanner has various options; you can choose SmartVIN to detect your vehicle automatically. However, you choose Manual Selection if SmartVIN does not work as intended. Click here to check out our article about Lexus VIN.
7. Select the Specific Model and Chassis: After selecting the vehicle make, scroll through the available models and select the correct one for your Lexus. Choose the corresponding chassis or body type to properly sync the scanner to your vehicle.
8. Select Control Units: Once you have selected the model and chassis, the scanner will let you choose between “Quick scan” or “Control Modules.” Control Modules display a list of control units or modules in your vehicle. Examples include the engine control module (ECM), transmission control module (TCM), and ABS control module. Choose the specific module you want to diagnose. Otherwise, you can also choose the  “Quick Scan” to check everything.
9. Interpret the Codes: Once the YOUCANIC scanner completes the code retrieval process, the displayed codes will provide information about specific issues detected by the control unit. Take note of these codes for further analysis and diagnosis. Each DTC consists of a letter and four numbers. The letter indicates the system affected, while the numbers describe the issue more specifically. Click here to learn more about fault codes.
10. Erase Codes: After the problem has been repaired, return to the scanner’s menu and select the option to “Erase Codes” or “Clear Codes.” This action removes the stored fault codes from the control unit’s memory, indicating that the problem has been resolved. Please note that you may or may not erase a code when the issue is not fixed.

NOTE: These pictures are just the demo of our YOUCANIC Scanner, it may or may not be the same but the procedure is the same.

DTCs or fault codes are like secret messages your Lexus conveys when something’s amiss. These alphanumeric codes are like humans’ Morse code. They provide clues to underlying issues, helping mechanics or DIY enthusiasts to diagnose and repair problems efficiently. Understanding DTCs empowers you, the Lexus owner, to stay informed about your vehicle’s health and make informed decisions during its maintenance.

Common Lexus Fault Codes

Here’s a list of 20 Lexus fault codes, along with brief explanations for each:

1. P0300 – Random/Multiple Cylinder Misfire Detected: Indicates misfires in multiple engine cylinders, potentially due to spark plug or ignition coil issues.
2. P0171 – System Too Lean (Bank 1): Suggests a lean fuel mixture in bank 1 of the engine, possibly due to a vacuum leak or fuel delivery problem.
3. P0420 – Catalyst System Efficiency Below Threshold (Bank 1): Indicates the catalytic converter’s efficiency is below the required threshold.
4. P0442 – Evaporative Emission System Leak Detected (small leak): A small leak was detected in the EVAP system, which handles fuel vapor emissions.
5. P0138 – O2 Sensor Circuit High Voltage (Bank 1, Sensor 2): The oxygen sensor in bank 1, sensor 2, is outputting high voltage, indicating a fuel mixture issue.
6. P0335 – Crankshaft Position Sensor ‘A’ Circuit Malfunction: Problems detected with the crankshaft position sensor circuit.
7. P0340 – Camshaft Position Sensor ‘A’ Circuit (Bank 1 or single sensor): Indicates an issue with the camshaft position sensor in bank 1.
8. P0135 – O2 Sensor Heater Circuit (Bank 1, Sensor 1): A problem was detected in the oxygen sensor heater circuit in Bank 1, sensor 1.
9. P0401 – Exhaust Gas Recirculation (EGR) Flow Insufficient: Insufficient flow detected in the EGR system.
10. P0430 – Catalyst System Efficiency Below Threshold (Bank 2): The catalytic converter’s efficiency in bank 2 is below the required threshold.
11. P0456 – Evaporative Emission System Leak Detected (very small leak): A very small leak was detected in the EVAP system.
12. P0700 – Transmission Control System Malfunction: General fault in the transmission control system.
13. P1346 – VVT Sensor Range/Performance Problem (Bank 1): Variable Valve Timing sensor in bank 1 is experiencing performance issues.
14. P1135 – Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1): Issues detected in the air/fuel ratio sensor heater circuit.
15. P0301 – Cylinder 1 Misfire Detected: Misfire has been detected specifically in cylinder 1.
16. P1121 – Throttle Position Sensor Inconsistent with Mass Air Flow Sensor: A discrepancy between the throttle position and mass air flow sensor readings.
17. P1568 – Cruise Control System Malfunction: Indicates a problem with the cruise control system.
18. P0155 – O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1): A malfunction in the oxygen sensor heater circuit in bank 2, sensor 1.
19. P1604 – Startability Malfunction: Issues detected with the vehicle’s startability.
20. P2135 – Throttle/Pedal Position Sensor/Switch ‘A’/’B’ Voltage Correlation: A discrepancy in voltage readings from the throttle/pedal position sensors.

These codes provide a starting point for diagnosing and addressing issues in Lexus vehicles. However, it’s always recommended to consult a qualified Lexus technician for precise diagnostics and repair.

What does OBD mean? How do I access it?

OBD stands for “On-Board Diagnostic.” Most modern vehicles now include an OBD port, which can be utilized by a scanner that communicates with your vehicle. An OBD-II scanner plugs into the socket, designed to help automotive technicians interpret faults and other issues that your Lexus may be experiencing or have recorded. Most Lexus now have OBD-II Ports, including RX, ES, LS, NX, UX, LC500, LX, and other newer models.

Now, your car has many parts that may seem overwhelming. Still, with this guide, we’ll delve into how to read, interpret, and erase codes, live data, and freeze frame data, as well as the significance of professional-grade scanners that could save you hundreds and thousands on repair if appropriately diagnosed.

Why can’t I clear the codes?

Once you’ve identified the DTCs, you may be tempted to clear them, hoping to continue driving your Lexus, and the problem magically disappears. Clearing the codes can temporarily remove the “Check Engine” light but doesn’t address the underlying issue. It will always come back. Here are also some lists of why you cannot clear the codes of your Lexus:

• Use a Professional-Grade Scanner: Ditch the generic scanner and upgrade to a professional-grade one like the YOUCANIC scanner. Generic scanners are like trying to open a Ferrari with a Ford key – it won’t work! YOUCANIC, on the other hand, is like the master key to your Lexus’ diagnostics, unlocking hidden diagnostic powers and letting you clear codes that would otherwise remain stubborn and hidden. Want to know what OBD-II Scanner is best for your Lexus? Check it out here.
• Underlying Issues: Before clearing fault codes, remember to address the underlying issue that triggered them in the first place. Clearing codes is like patching a leaky pipe without fixing the cracked valve – it’s just a temporary fix. The ‘check engine’ light will surely come back and haunt you.
• Continuous Fault Monitoring: Like the SRS system, certain fault codes may be cleared by disconnecting the battery (like a reset). They will reappear even after clearing until the root cause is resolved. It is a persistent reminder to fix the problem, not just mask it.
• Proper Clearing Procedure: Following the correct steps outlined in your diagnostic scanner’s user manual is essential to clear fault codes effectively. If unsure about the clearing procedure, consult a professional for guidance specific to your scanner and Chrysler model.

YOUCANIC Full System Car Diagnostic Scanner

What do History, Current, and Stored DTCs do?

1. History: These codes indicate past issues that have resolved themselves or are no longer causing the “Check Engine” light to illuminate. They typically do not require immediate attention.
2. Current Codes: These codes represent current or active problems that require immediate diagnosis. They indicate a present issue or malfunction in a specific system or component of the vehicle that needs to be addressed. They will remain displayed until the underlying issue is resolved.
3. Stored Codes: These codes are inactive but remain stored in the computer’s memory, recording previous issues. These can provide additional information about past issues as a historical reference for previous faults. While they may not be active, they can offer insights into the vehicle’s history and aid in the diagnostic process.

Please click here to learn more about the history, current, and stored DTCs.

What is the purpose of Live Data and Freeze data?

Live data allows you to monitor real-time sensor readings, providing valuable insights into the car’s operation. On the other hand, Freeze frame data captures a snapshot of vehicle conditions when a fault code is triggered. Analyzing this data provides context and aids in pinpointing the root cause of the issue.

Frequently Asked Questions:

Lexus is a leading luxury car brand known for its high quality, advanced technology, and luxurious design. Remember, your Lexus deserves the best care, and understanding DTCs is crucial in maintaining its peak performance and ensuring your driving pleasure remains uninterrupted.

References:

1. What Is an OBD2 Scanner and How Does It Work?
   What Is an OBD2 Scanner and How Does It Work? | The Drive
2. DTC Fault Codes
   DTC Fault Codes – YOUCANIC
3. What Does the Check Engine Light Look Like, and What Does It Mean?
   What Does the Check Engine Light Look Like, and Really Mean? – Consumer Reports
4. Current / Stored / Active / Past / History Fault Codes Explained
   Current / Stored / Active / Past / History Fault Codes Explained – YOUCANIC

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