AutoCodes – Scion – C1278 Scion

C1278 Scion 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 Scion 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.
AI answers can be wrong. Verify repairs with testing. Open full chat
Code Popularity 1,031
How popular is this code, among other codes? Low
Table of contents Created and updated by William Orellana on Mar 21, 2024
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Code C1278 Scion 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 Scion - Abnormal Change in Output Signal of Rear Speed Sensor Left - AutoCodes.com
C1278 Scion Code - Abnormal Change in Output Signal of Rear Speed Sensor Left

What are the Possible Causes of the DTC C1278 Scion?

  • 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 Scion?

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.

Code Tech Notes

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the C1278 Scion 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.

Need more information about the C1278 Scion code?

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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 Scion Code

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

- The common symptoms include traction control and ABS warning lights illuminated on the dashboard, erratic behavior of the vehicle's traction control system, and potential loss of stability while driving.

2. What are the possible causes of OBDII code C1278 in a Scion indicating an abnormal change in output signal of the rear speed sensor left?

- The code C1278 in a Scion can be triggered by issues such as a faulty rear speed sensor left, damaged wiring or connectors in the sensor circuit, or problems with the ABS module.

3. How can I diagnose the source of OBDII code C1278 in my Scion related to the rear speed sensor left?

- To diagnose the issue, you can use an OBDII scanner to read the code, inspect the rear speed sensor left for any physical damage or corrosion, check the sensor's wiring and connectors for continuity, and perform a visual inspection of the ABS module.

4. Can I continue driving my Scion with OBDII code C1278 indicating a problem with the rear speed sensor left?

- It is not recommended to drive the vehicle with this code present, as it can affect the proper functioning of the traction control system and ABS, potentially compromising your safety on the road.

5. How can I repair OBDII code C1278 in my Scion caused by an abnormal change in output signal of the rear speed sensor left?

- Repair options include replacing the rear speed sensor left if it is faulty, repairing or replacing damaged wiring or connectors, and resetting the ABS module to clear the code.

6. Are there any DIY tips for fixing OBDII code C1278 related to the rear speed sensor left in a Scion?

- While some basic inspections and checks can be done at home, diagnosing and repairing this code may require specialized tools and expertise. It is advisable to consult a professional mechanic for accurate diagnosis and repair.

7. How much does it typically cost to repair OBDII code C1278 in a Scion due to an abnormal change in output signal of the rear speed sensor left?

- Repair costs can vary depending on the exact cause of the issue, but replacing a rear speed sensor left can range from $100 to $300, while addressing wiring or module problems may incur additional expenses.

8. Will resetting the OBDII code C1278 in my Scion resolve the issue related to the rear speed sensor left?

- Resetting the code may temporarily clear the warning lights, but it will not fix the underlying problem causing the abnormal output signal from the rear speed sensor left. Professional diagnosis and repair are recommended.

9. Can extreme weather conditions affect the rear speed sensor left and trigger OBDII code C1278 in a Scion?

- Yes, extreme temperatures or moisture exposure can impact the sensor's performance and lead to code C1278. It's essential to keep the sensor and its connections protected from harsh environmental conditions.

10. Is it necessary to replace both rear speed sensors if OBDII code C1278 only indicates an issue with the rear speed sensor left in a Scion?

- While it's not mandatory to replace both sensors, it's advisable to inspect the right rear speed sensor as well to ensure both sides are functioning correctly. If needed, replace the faulty sensor to maintain balanced performance.

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