AutoCodes – GMC – P128B GMC

P128B GMC Code - Fuel Rail Pressure Sensor 2 Internal Performance

Quick Answer

The Engine Control Module (ECM) uses the Fuel Rail Pressure (FRP) sensor to constantly adjust the high-pressure fuel pump's feed rate so that the ideal pressure is permanently maintained in the high-pressure section (between the high-pressure fuel pump and the injectors) by means of closed-loop control. Common causes include Low or no fuel, Faulty Fuel Rail Pressure (FRP) Sensor, Fuel Rail Pressure 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: P128B GMC indicates Fuel Rail Pressure Sensor 2 Internal Performance.
Common causes: Common causes include Low or no fuel, Faulty Fuel Rail Pressure (FRP) Sensor, Fuel Rail Pressure 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 1,792

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 May 30, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P128B GMC Description

The Engine Control Module (ECM) uses the Fuel Rail Pressure (FRP) sensor to constantly adjust the high-pressure fuel pump's feed rate so that the ideal pressure is permanently maintained in the high-pressure section (between the high-pressure fuel pump and the injectors) by means of closed-loop control. The fuel rail pressure sensor transmits fuel pressure and temperature information via serial data to the ECM. When the fuel pressure is high, the signal voltage is high. When the fuel pressure is low, the signal voltage is low. The ECM controls the fuel pressure regulator, which regulates high-pressure fuel that goes to the fuel injector rails and the injectors. The Diagnostic Trouble Code (DTC) will be set if the Fuel Rail Pressure Sensor 2 is greater than a predefined threshold for greater than 2.6 s

OBDII Code P128B GMC - Fuel Rail Pressure Sensor 2 Internal Performance - AutoCodes.com — P128B GMC Code - Fuel Rail Pressure Sensor 2 Internal Performance

What does this mean?

What are the Possible Causes of the DTC P128B GMC?

Low or no fuel
Faulty Fuel Rail Pressure (FRP) Sensor
Fuel Rail Pressure harness is open or shorted
Fuel Rail Pressure circuit poor electrical connection
Faulty Fuel Pump

How to Fix the DTC P128B GMC?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P128B GMC 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 P128B GMC code?

Need more information on how to fix the P128B GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P128B GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P128B 2014 GMC Sierra — Fuel Rail Pressure Sensor 2 Internal Performance
P128B 2015 GMC Sierra — Fuel Rail Pressure Sensor 2 Internal Performance
P128B 2016 GMC Sierra — Fuel Rail Pressure Sensor 2 Internal Performance
P128B 2017 GMC Sierra — Fuel Rail Pressure Sensor 2 Internal Performance
P128B 2018 GMC Sierra — Fuel Rail Pressure Sensor 2 Internal Performance

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 P128B GMC Code

1. What are the common symptoms of OBDII code P128B GMC related to the Fuel Rail Pressure Sensor 2 Internal Performance?

The common symptoms include poor engine performance, rough idling, decreased fuel efficiency, and potential stalling.

2. What are the possible causes of OBDII code P128B GMC?

Possible causes can include a faulty fuel rail pressure sensor, issues with the fuel pump, clogged fuel filter, wiring problems, or a problem with the fuel pressure regulator.

3. How serious is OBDII code P128B GMC?

While the severity can vary, it is recommended to address this issue promptly to avoid potential engine damage and further performance issues.

4. How can I diagnose OBDII code P128B GMC?

Diagnosis typically involves using an OBDII scanner to retrieve the code, inspecting the fuel rail pressure sensor and related components, and testing the fuel system for proper operation.

5. Can I continue driving with OBDII code P128B GMC triggered?

It is generally not recommended to drive with this code active, as it can lead to further damage and potentially unsafe driving conditions.

6. What are some repair tips for fixing OBDII code P128B GMC?

Repair tips may include replacing the fuel rail pressure sensor, checking and cleaning the fuel system components, ensuring proper wiring connections, and verifying fuel pressure readings.

7. How much does it cost to repair OBDII code P128B GMC?

The cost of repair can vary depending on the specific cause of the issue, but it may involve parts and labor expenses ranging from $100 to $500 or more.

8. Can I reset OBDII code P128B GMC without fixing the underlying issue?

While you can clear the code temporarily, it is important to address the root cause to prevent the code from reoccurring and potential engine problems.

9. Are there any preventive measures to avoid OBDII code P128B GMC?

Regular maintenance of the fuel system, including timely fuel filter replacements and inspections, can help prevent issues leading to this trouble code.

10. Can a DIY enthusiast fix OBDII code P128B GMC, or is professional help necessary?

Depending on the individual's skills and tools available, some DIY enthusiasts may be able to address this code, but professional help is recommended for accurate diagnosis and proper repairs.