AutoCodes – Lexus – C1278 Lexus

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

Quick Answer

The speed sensor detects the wheel speed and sends the appropriate signals to the Skid Control ECU (Brake Actuator Assembly). Common causes include Faulty Rear Speed Sensor Left, Rear Speed Sensor Left Rotor (Rear Axle Hub and Bearing Assembly Left), Rear Speed Sensor Left harness is open or shorted. 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 Faulty Rear Speed Sensor Left, Rear Speed Sensor Left Rotor (Rear Axle Hub and Bearing Assembly Left), Rear Speed Sensor Left harness is open or shorted.
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.

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Code Popularity 1,930

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 21, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code C1278 Lexus Description

The speed sensor detects the wheel speed and sends the appropriate signals to the Skid Control ECU (Brake Actuator Assembly). These signals are used for Anti-Lock Brake System (ABS) control. Speed sensor rotors have rows of alternating N and S magnetic poles, and their magnetic fields change when the rotors turn. Each speed sensor detects that magnetic change and sends a pulse signal to the Skid Control ECU (Brake Actuator Assembly).

OBDII Code C1278 Lexus - Abnormal Change in Output Signal of Rear Speed Sensor Left - AutoCodes.com — C1278 Lexus Code - Abnormal Change in Output Signal of Rear Speed Sensor Left

What does this mean?

What are the Possible Causes of the DTC C1278 Lexus?

Faulty Rear Speed Sensor Left
Rear Speed Sensor Left Rotor (Rear Axle Hub and Bearing Assembly Left)
Rear Speed Sensor Left harness is open or shorted
Rear Speed Sensor Left circuit poor electrical connection

How to Fix the DTC C1278 Lexus?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the C1278 Lexus code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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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.