Toyota AVALON The 6 Most Common OBD DTC

by erwincsalarda · April 16, 2023

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Toyota AVALON The 6 Most Common OBD DTC Problems

Toyota Avalon owners should know the most common OBD Diagnostic Trouble Codes (DTC) so they can figure out what might be wrong with their car and fix it. In this article, we list the 6 most common DTC codes for Toyota Avalon cars, which are P0500, P1604, P0171, C1201, C1301, and B150A. By getting to know these codes, you can find problems more quickly and keep your Avalon running well and reliably.

DTC Code: P0500 – Vehicle Speed Sensor “A” Malfunction

Description: The P0500 code indicates a malfunction in the vehicle speed sensor circuit “A.” This sensor measures the speed of the vehicle and sends that information to the Engine Control Module (ECM), Transmission Control Module (TCM), and other relevant systems.

Symptoms:

Speedometer not working or intermittent
Harsh or erratic shifting
Reduced fuel efficiency
Illuminated Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL)
Traction Control System (TCS) or Anti-Lock Brake System (ABS) warning light
Poor acceleration
Cruise control not functioning

Cause:

Faulty vehicle speed sensor
Damaged or corroded wiring or connectors
Malfunctioning ECM or TCM
Faulty speedometer instrument cluster
Damaged wheel bearing or hub assembly

Possible Location:

Vehicle speed sensor (usually located on the transmission or near the wheel hub assembly)
Wiring harnesses connected to the vehicle speed sensor
ECM or TCM

How to Fix the Problem:

Inspect the vehicle speed sensor and its wiring for damage, corrosion, or loose connections. Repair or replace as needed.
Test the vehicle speed sensor with a multimeter to ensure it is functioning properly. Replace the sensor if faulty.
Check the wheel bearing and hub assembly for damage or excessive play. Repair or replace as needed.
Inspect and test the ECM, TCM, and speedometer instrument cluster. Repair or replace if necessary.

How Difficult to Fix: Moderate. DIYers with some automotive knowledge and experience can perform most of the diagnostic and repair steps. However, working with the ECM or TCM may require specialized equipment and expertise.

Can You Drive With This Code: It is not recommended to drive with this code, as it can lead to erratic shifting, poor acceleration, and reduced safety features such as TCS and ABS.

How to Clear the Code: After fixing the problem, clear the code with an OBD-II scanner. Disconnecting the battery may reset the code and the ECM’s learned data, but it is not the preferred method. It’s important to address the underlying issue and use a proper scan tool to reset the code.

Tools Needed to Use:

OBD-II scanner – to read and clear the code
Multimeter – to test the vehicle speed sensor and wiring
Basic hand tools – for removing and installing components
Specialized tools – for diagnosing and repairing ECM or TCM issues (if applicable)

DTC Code: P1604 – Startability Malfunction

Description: The P1604 code indicates that the Engine Control Module (ECM) has detected a startability problem, meaning the engine is unable to start or experiences difficulty starting. This code is specific to Toyota and Lexus vehicles, including the Avalon.

Symptoms:

Difficulty starting the engine
Engine cranking but not starting
Intermittent starting issues
Illuminated Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL)

Cause:

Weak or dead battery
Faulty starter motor or solenoid
Poor electrical connections in the starting circuit
Malfunctioning ignition switch
Faulty fuel pump or fuel pump relay
Clogged fuel filter
Faulty ECM

Possible Location:

Battery
Starter motor and solenoid
Starting circuit wiring and connections
Ignition switch
Fuel pump and fuel pump relay
Fuel filter
ECM

How to Fix the Problem:

Test the battery for proper voltage and health. Charge or replace the battery if necessary.
Inspect the starter motor and solenoid for damage or wear. Test their operation and replace if necessary.
Check the starting circuit wiring and connections for corrosion, damage, or loose connections. Repair or replace as needed.
Test the ignition switch for proper operation. Replace if faulty.
Check the fuel pump and fuel pump relay for proper operation. Replace if necessary.
Inspect the fuel filter for clogs and replace if needed.
Test the ECM for proper operation and replace if necessary.

How Difficult to Fix: Moderate. Some steps, such as testing and replacing the battery, can be performed by DIYers. However, diagnosing and repairing issues with the ECM or starter motor may require specialized tools and expertise.

Can You Drive With This Code: Driving with this code is not recommended, as it indicates an issue with the engine’s ability to start. This can lead to a no-start situation, leaving you stranded.

Tools Needed to Use:

OBD-II scanner – to read and clear the code
Multimeter – to test the battery, starter motor, and other electrical components
Basic hand tools – for removing and installing components
Specialized tools – for diagnosing and repairing ECM or starter motor issues (if applicable)

DTC Code: P0171 – System Too Lean (Bank 1)

Description: The P0171 code indicates that the air-fuel mixture in Bank 1 (the side of the engine with cylinder 1) is too lean, meaning there is too much air and not enough fuel. The Engine Control Module (ECM) monitors the air-fuel ratio and triggers the code when it detects an imbalance.

Symptoms:

Rough idle
Hesitation or stalling during acceleration
Reduced fuel efficiency
Loss of power
Illuminated Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL)

Cause:

Vacuum leaks (hoses, intake manifold gaskets, etc.)
Faulty Mass Air Flow (MAF) sensor
Faulty oxygen sensor (pre-catalytic converter)
Dirty or clogged fuel injectors
Low fuel pressure (due to a faulty fuel pump or fuel pressure regulator)
Faulty ECM

Possible Location:

Vacuum hoses and connections
Intake manifold gaskets
Mass Air Flow sensor
Oxygen sensor (pre-catalytic converter)
Fuel injectors
Fuel pump and fuel pressure regulator
ECM

How to Fix the Problem:

Inspect vacuum hoses and connections for damage or leaks. Repair or replace as needed.
Check the intake manifold gaskets for leaks. Replace if necessary.
Test the Mass Air Flow sensor with a multimeter or scan tool. Clean or replace if necessary.
Inspect and test the pre-catalytic converter oxygen sensor. Replace if faulty.
Clean or replace dirty or clogged fuel injectors.
Test the fuel pump and fuel pressure regulator for proper operation. Replace if necessary.
Inspect and test the ECM for proper operation. Replace if necessary.

How Difficult to Fix: Moderate. Some steps can be performed by DIYers with basic automotive knowledge. However, diagnosing and repairing issues with the ECM or fuel system may require specialized tools and expertise.

Can You Drive With This Code: Driving with this code is not recommended, as it can lead to poor engine performance, reduced fuel efficiency, and potential damage to the catalytic converter.

Tools Needed to Use:

OBD-II scanner – to read and clear the code
Multimeter – to test electrical components such as the MAF sensor and oxygen sensor
Basic hand tools – for removing and installing components
Specialized tools – for diagnosing and repairing ECM or fuel system issues (if applicable)
Fuel pressure gauge – to test fuel pressure (if necessary)

DTC Code: C1201 – Engine Control System Malfunction

Description: The C1201 code indicates that the Engine Control Module (ECM) has detected a malfunction in the engine control system, which can affect the operation of the Anti-Lock Brake System (ABS) and Traction Control System (TCS). This code is typically triggered when there is an issue with the engine that could impact vehicle stability.

Symptoms:

Reduced engine performance
Illuminated Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL)
ABS and/or TCS warning light
Poor acceleration
Rough idle

Cause:

Faulty engine sensors (e.g., Mass Air Flow sensor, oxygen sensor, etc.)
Vacuum leaks
Ignition system issues
Fuel system problems
Faulty ECM

Possible Location:

Engine sensors
Vacuum hoses and connections
Ignition system components
Fuel system components
ECM

How to Fix the Problem:

Use an OBD-II scanner to check for any engine-related DTC codes that may provide more specific information about the issue.
Inspect engine sensors for damage or malfunction. Repair or replace as needed.
Check vacuum hoses and connections for damage or leaks. Repair or replace as necessary.
Inspect the ignition system components (spark plugs, ignition coils, etc.) for damage or wear. Replace if necessary.
Diagnose and repair any fuel system issues (e.g., clogged fuel injectors, faulty fuel pump, etc.).
Test the ECM for proper operation. Replace if necessary.

How Difficult to Fix: Moderate to Difficult. Some steps can be performed by DIYers with basic automotive knowledge, while others may require specialized tools and expertise, particularly when diagnosing and repairing issues with the ECM.

Can You Drive With This Code: Driving with this code is not recommended, as it can lead to poor engine performance, reduced fuel efficiency, and compromised safety features such as ABS and TCS.

Tools Needed to Use:

OBD-II scanner – to read and clear the code
Multimeter – to test electrical components such as engine sensors
Basic hand tools – for removing and installing components
Specialized tools – for diagnosing and repairing ECM issues (if applicable)
Fuel pressure gauge – to test fuel pressure (if necessary)

DTC Code: C1301 – Brake Hydraulic Pressure Sensor Circuit Failure

Description: The C1301 code indicates that there is a problem with the brake hydraulic pressure sensor circuit. This sensor measures the hydraulic pressure in the brake system and sends that information to the Anti-Lock Brake System (ABS) module. A fault in this circuit can lead to poor braking performance and ABS malfunction.

Symptoms:

ABS warning light illuminated
Traction Control System (TCS) warning light illuminated
Reduced braking performance
Brake pedal feels harder or softer than usual
Brake system warning light illuminated (in some cases)

Cause:

Faulty brake hydraulic pressure sensor
Damaged or corroded wiring or connectors in the sensor circuit
Low brake fluid level
Air in the brake system
Malfunctioning ABS module

Possible Location:

Brake hydraulic pressure sensor (located in the brake system, often near the master cylinder)
Wiring harnesses connected to the brake hydraulic pressure sensor
Brake fluid reservoir
ABS module

How to Fix the Problem:

Inspect the brake hydraulic pressure sensor and its wiring for damage, corrosion, or loose connections. Repair or replace as needed.
Test the brake hydraulic pressure sensor with a multimeter to ensure it is functioning properly. Replace the sensor if faulty.
Check the brake fluid level and top off if necessary. Inspect for any leaks in the brake system.
Bleed the brake system to remove any air that may be trapped in the lines.
Inspect and test the ABS module for proper operation. Repair or replace if necessary.

How Difficult to Fix: Moderate. Some steps, such as checking the brake fluid level and bleeding the brake system, can be performed by DIYers with basic automotive knowledge. However, diagnosing and repairing issues with the brake hydraulic pressure sensor or ABS module may require specialized tools and expertise.

Can You Drive With This Code: It is not recommended to drive with this code, as it can lead to reduced braking performance and compromised safety features such as ABS and TCS.

How to Clear the Code: After fixing the problem, clear the code with an OBD-II scanner specifically designed to read ABS codes. Disconnecting the battery may reset the code and the ABS module’s learned data, but it is not the preferred method. It’s important to address the underlying issue and use a proper scan tool to reset the code.

Tools Needed to Use:

OBD-II scanner with ABS capabilities – to read and clear the code
Multimeter – to test the brake hydraulic pressure sensor and wiring
Basic hand tools – for removing and installing components
Brake bleeder kit – for bleeding the brake system
Specialized tools – for diagnosing and repairing ABS module issues (if applicable)

DTC Code: B150A – Front Pretensioner Squib LH Circuit Malfunction

Description: The B150A code indicates that there is a malfunction in the front pretensioner squib (igniter) circuit for the left-hand (driver’s side) seat belt. The pretensioner is a crucial part of the seat belt system that tightens the belt in the event of a collision, helping to reduce the risk of injury.

Symptoms:

Airbag warning light illuminated
Seat belt warning light illuminated
Seat belt pretensioner not working properly during a collision

Cause:

Faulty front seat belt pretensioner squib (igniter)
Damaged or corroded wiring or connectors in the pretensioner circuit
Faulty Airbag Control Module (ACM)

Possible Location:

- Front left seat belt pretensioner
- Wiring harnesses connected to the pretensioner
- Airbag Control Module

How to Fix the Problem:

Inspect the front left seat belt pretensioner and its wiring for damage, corrosion, or loose connections. Repair or replace as needed.
Test the pretensioner squib with a multimeter or scan tool to ensure it is functioning properly. Replace the pretensioner if faulty.
Inspect and test the Airbag Control Module for proper operation. Repair or replace if necessary.

How Difficult to Fix: Moderate. Some steps can be performed by DIYers with basic automotive knowledge. However, diagnosing and repairing issues with the airbag control module and pretensioner squib may require specialized tools and expertise.

Can You Drive With This Code: While it may be possible to drive with this code, it is not recommended as it can compromise the safety of the driver during a collision due to a malfunctioning seat belt pretensioner.

How to Clear the Code: After fixing the problem, clear the code with an OBD-II scanner specifically designed to read airbag (SRS) codes. Disconnecting the battery may reset the code and the Airbag Control Module’s learned data, but it is not the preferred method. It’s important to address the underlying issue and use a proper scan tool to reset the code.

Tools Needed to Use:

OBD-II scanner with SRS capabilities – to read and clear the code
Multimeter – to test the pretensioner squib and wiring
Basic hand tools – for removing and installing components
Specialized tools – for diagnosing and repairing Airbag Control Module issues (if applicable)

WORDS FROM ERWIN SALARDA

Understanding the top six most common OBD-II trouble codes for Toyota Avalon vehicles is key to proper maintenance and timely repairs. By staying aware of these issues and their respective solutions, you can prolong the life of your Avalon and enhance its overall performance. Remember that addressing problems early on can save you from expensive repairs down the line.