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C1278 Lexus Code - Abnormal Change in Output Signal of Rear Speed Sensor Left

Quick Answer

The C1278 diagnostic trouble code (DTC) for Lexus vehicles indicates an abnormal change in the output signal of the rear speed sensor located on the left side of the vehicle. Common causes include Malfunctioning rear speed sensor, Damaged or corroded sensor wiring or connectors, Debris or foreign objects interfering with sensor performance. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
C1278 Lexus indicates Abnormal Change in Output Signal of Rear Speed Sensor Left.
Common causes
Common causes include Malfunctioning rear speed sensor, Damaged or corroded sensor wiring or connectors, Debris or foreign objects interfering with sensor performance.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code C1278 Lexus Description

The C1278 diagnostic trouble code (DTC) for Lexus vehicles indicates an abnormal change in the output signal of the rear speed sensor located on the left side of the vehicle. The rear speed sensor is a crucial component of the vehicle's anti-lock braking system (ABS) and electronic stability control (ESC) system. It is responsible for monitoring the speed of the rear wheels and sending this information to the vehicle's onboard computer.

OBDII Code C1278 Lexus - Abnormal Change in Output Signal of Rear Speed Sensor Left
C1278 Lexus Code - Abnormal Change in Output Signal of Rear Speed Sensor Left

Common Causes of C1278 Lexus

  1. Malfunctioning rear speed sensor
  2. Damaged or corroded sensor wiring or connectors
  3. Debris or foreign objects interfering with sensor performance
  4. Faulty ABS or ESC control module
  5. Electrical issues, such as blown fuses or short circuits

Symptoms of C1278 Lexus

  1. ABS warning light illuminated on the dashboard
  2. ESC system malfunction warning message displayed
  3. Erratic braking behavior, such as unexplained pulsation or vibration during braking
  4. Loss of traction control on slippery road surfaces
  5. Increased stopping distances during emergency braking situations

How to Fix C1278 Lexus

  1. Begin by performing a comprehensive diagnostic scan using a professional OBD-II scanner to retrieve the specific trouble codes and confirm the issue with the rear speed sensor.
  2. Inspect the rear speed sensor on the left side of the vehicle for any signs of damage, corrosion, or contamination. Clean the sensor and its surroundings if necessary.
  3. Check the sensor wiring harness and connectors for any visible damage or loose connections. Repair or replace any faulty wiring as needed.
  4. Test the rear speed sensor using a multimeter to ensure it is functioning within the manufacturer's specified parameters. Replace the sensor if it fails the test.
  5. Clear the DTCs from the vehicle's computer memory and road test the vehicle to confirm that the ABS and ESC systems are functioning correctly without any warning lights or abnormal behavior.

Cost to Fix C1278 Lexus

The typical repair costs for addressing the C1278 code on a Lexus vehicle can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, replacing a rear speed sensor or repairing damaged wiring can range from $150 to $300, including parts and labor. However, additional costs may apply if the ABS or ESC control module requires replacement or reprogramming.

What does this mean?

Tech Notes for C1278 Lexus

Because the Rear Axle Hub and Bearing Assembly cannot be disassembled, if the Rear Speed Sensor needs replacement, replace the Rear Axle Hub and Bearing Assembly.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about C1278 Lexus Code

1. What are the common symptoms of OBDII code C1278 in a Lexus related to an abnormal change in output signal of the rear speed sensor left?

- Common symptoms include erratic ABS operation, traction control issues, and the activation of the vehicle's stability control system.

2. What are the potential causes of OBDII code C1278 in a Lexus?

- Possible causes include a faulty rear speed sensor left, damaged wiring or connectors, a problem with the ABS module, or issues with the wheel speed sensor tone ring.

3. How can I diagnose the source of the OBDII code C1278 in my Lexus?

- Diagnosis typically involves inspecting the rear speed sensor left and its wiring for any damage, checking the connectors for proper connection, and testing the ABS module for fault codes.

4. Can I continue driving my Lexus with OBDII code C1278 present?

- It is not recommended to continue driving with this code present, as it can affect the performance of the ABS system and compromise vehicle safety.

5. What are some repair tips for addressing OBDII code C1278 in a Lexus?

- Repair tips may include replacing the rear speed sensor left, repairing damaged wiring or connectors, resetting the ABS system, and ensuring proper installation of components.

6. Is it possible to clear the OBDII code C1278 in a Lexus without fixing the underlying issue?

- While clearing the code may temporarily turn off the warning light, the issue will likely reoccur until the root cause is addressed.

7. How do I reset the ABS system after repairing the issue related to OBDII code C1278 in my Lexus?

- Resetting the ABS system may require using a diagnostic tool to clear the fault codes and recalibrate the system. Consult your vehicle's manual or a professional for specific instructions.

8. Can extreme weather conditions or road debris trigger OBDII code C1278 in a Lexus?

- Yes, extreme weather conditions or road debris can potentially damage the rear speed sensor left or its wiring, leading to the abnormal change in output signal detected by the system.

9. What role does the rear speed sensor left play in the overall operation of the ABS system in a Lexus?

- The rear speed sensor left provides crucial data on wheel speed to the ABS system, allowing for proper operation of anti-lock braking and stability control features.

10. Are there any recalls or technical service bulletins related to OBDII code C1278 in Lexus vehicles?

- It's recommended to check with Lexus dealerships or online databases for any recalls or technical service bulletins specific to OBDII code C1278 and related issues in Lexus vehicles.

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