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Engine-Codes – GMC – P128C 2014 GMC Sierra

P128C 2014 GMC Sierra Code - Fuel Rail Temperature Sensor 1 Signal Message Counter Incorrect

Quick Answer

The P128C diagnostic trouble code (DTC) for a 2014 GMC Sierra indicates that there is an issue with the Fuel Rail Temperature Sensor 1 Signal Message Counter being incorrect. Common causes include Faulty Fuel Rail Temperature Sensor, Damaged wiring or connectors, Malfunctioning ECM. 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
P128C 2014 GMC Sierra indicates Fuel Rail Temperature Sensor 1 Signal Message Counter Incorrect.
Common causes
Common causes include Faulty Fuel Rail Temperature Sensor, Damaged wiring or connectors, Malfunctioning ECM.
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 17, 2024
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Code P128C 2014 GMC Sierra Description

The P128C diagnostic trouble code (DTC) for a 2014 GMC Sierra indicates that there is an issue with the Fuel Rail Temperature Sensor 1 Signal Message Counter being incorrect. The Fuel Rail Temperature Sensor is a crucial component that measures the temperature of the fuel in the fuel rail. This information is essential for the engine control module (ECM) to adjust the fuel mixture and timing to ensure optimal engine performance and efficiency. When the signal message counter is incorrect, it means that the ECM is not receiving the expected number of messages from the sensor, leading to potential issues with fuel delivery and engine operation.

OBDII Code P128C 2014 GMC Sierra - Fuel Rail Temperature Sensor 1 Signal Message Counter Incorrect
P128C 2014 GMC Sierra Code - Fuel Rail Temperature Sensor 1 Signal Message Counter Incorrect

Common Causes of P128C 2014 GMC Sierra

  1. Faulty Fuel Rail Temperature Sensor
  2. Damaged wiring or connectors
  3. Malfunctioning ECM
  4. Software glitch in the ECM
  5. Poor electrical connection

Symptoms of P128C 2014 GMC Sierra

  1. Decreased fuel efficiency
  2. Rough idling or stalling
  3. Hesitation or lack of power during acceleration
  4. Engine misfires
  5. Illumination of the check engine light

How to Fix P128C 2014 GMC Sierra

  1. Begin by connecting a diagnostic scanner to the vehicle's OBD-II port to retrieve the specific DTC and confirm the issue with the Fuel Rail Temperature Sensor.
  2. Inspect the sensor, wiring, and connectors for any visible damage or corrosion. Replace any faulty components as needed.
  3. Clear the DTC from the ECM's memory using the diagnostic scanner and monitor the sensor's data to ensure it is providing accurate readings.
  4. If the issue persists, further diagnostic testing may be required to pinpoint the exact cause, such as testing the ECM or checking for software updates.
  5. Once the root cause is identified, perform the necessary repairs or replacements to resolve the P128C code and ensure proper functioning of the Fuel Rail Temperature Sensor.

Cost to Fix P128C 2014 GMC Sierra

The typical repair costs for addressing a P128C code on a 2014 GMC Sierra can vary depending on the specific cause of the issue. In general, replacing a faulty Fuel Rail Temperature Sensor can cost between $100 and $200, while addressing wiring or connector issues may range from $50 to $150. If the ECM needs to be replaced or reprogrammed, the cost can increase significantly, potentially exceeding $500. Labor rates at auto repair shops typically range from $80 to $150 per hour, so the total cost can vary based on the time required for diagnosis and repair. It is advisable to consult with a trusted mechanic or dealership for a more accurate estimate based on your vehicle's specific needs and location.

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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 P128C 2014 GMC Sierra Code

1. What does the OBDII code P128C mean on a 2014 GMC Sierra?

The P128C code indicates that the Fuel Rail Temperature Sensor 1 has an incorrect signal message counter, meaning the sensor's communication with the ECM is faulty or inconsistent.

2. What are the symptoms of the P128C code in a 2014 GMC Sierra?

Symptoms may include reduced engine performance, poor fuel efficiency, difficulty starting, or the check engine light being illuminated.

3. What causes the P128C code to appear on a 2014 GMC Sierra?

Common causes include a faulty fuel rail temperature sensor, damaged wiring or connectors, or issues with the ECM software.

4. Can I drive my 2014 GMC Sierra with a P128C code?

While the vehicle may still be drivable, it’s not recommended as it can lead to reduced performance, potential damage to engine components, or unsafe driving conditions.

5. How do I fix the P128C code on a 2014 GMC Sierra?

Repairs may involve inspecting and repairing damaged wiring or connectors, replacing the fuel rail temperature sensor, or reprogramming/refreshing the ECM software.

6. How much does it cost to fix the P128C code on a 2014 GMC Sierra?

The cost depends on the exact issue, but replacing the fuel rail temperature sensor usually costs $150–$300, including parts and labor. Wiring repairs or ECM reprogramming could vary.

7. Can a faulty fuel rail temperature sensor cause other problems?

Yes, a malfunctioning sensor can lead to incorrect fuel delivery, poor engine performance, and potential long-term engine damage if not addressed.

8. How can I diagnose the P128C code on my 2014 GMC Sierra?

Use an OBDII scanner to confirm the code, then inspect the fuel rail temperature sensor, wiring, and connectors for damage. Advanced diagnostics may require a multimeter or professional tools.

9. Does the P128C code require ECM replacement?

Not necessarily. ECM replacement is a last resort, as the issue is often resolved with sensor replacement, wiring repairs, or software updates.

10. Will clearing the P128C code fix the problem permanently?

Clearing the code may temporarily turn off the check engine light, but the issue will likely return unless the underlying problem is resolved.

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