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AutoCodes – GMC – B127B 2018 GMC Sierra

B127B 2018 GMC Sierra Code - Rearview Camera Input Signal Circuit

Quick Answer

When the transmission is placed into R, a 12 V signal is sent to the Rearview Camera indicating that camera operation is requested. Common causes include Faulty Rearview Camera, Rearview Camera harness is open or shorted, Rearview Camera circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means
B127B 2018 GMC Sierra indicates Rearview Camera Input Signal Circuit.
Common causes
Common causes include Faulty Rearview Camera, Rearview Camera harness is open or shorted, Rearview Camera circuit poor electrical connection.
Severity
Moderate - service should be scheduled soon.
Can I drive?
The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
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Code Popularity 334
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Nov 29, 2024
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Code B127B 2018 GMC Sierra Description

When the transmission is placed into R, a 12 V signal is sent to the Rearview Camera indicating that camera operation is requested. Ignition voltage and ground are supplied to the Rearview Camera. The Rearview Camera sends a video image to the Human Machine Interface Control Module Bypass Module through a video signal + and a video signal − circuit. The Human Machine Interface Control Module Bypass Module passes the video image to Human Machine Interface Control Module via video signal + and a video signal − circuits. The Human Machine Interface Control Module Bypass Module is used to ensure the Human Machine Interface Control Module produces a quality rear vision camera image to be displayed on the Info Display Module when the vehicle is placed in reverse gear. In the event, the Human Machine Interface Control Module Bypass Module detects an issue with the camera image generated by the Human Machine Interface Control Module, such as black, solid color, frozen, or image other than the camera image, the Human Machine Interface Control Module Bypass Module will assume control of the image to the Info Display Module and displays a raw camera image with no park assist projection lines or object detection symbols for the entire reverse cycle.
The Human Machine Interface Control Module Bypass Module is part of the video signal + and a video signal − circuits path from the Rearview Camera to the Human Machine Interface Control Module as well as the digital Low Voltage Differential Signaling (LVDS) path (USB cable) between the Human Machine Interface Control Module and Info Display Module and needs to be active for either signal to be received by these modules. The Human Machine Interface Control Module Bypass Module is not connected to serial data and uses the reverse lamp voltage input to determine the vehicle gear state.
The Diagnostic Trouble Code (DTC) will be set when the video signal from the rearview camera has not been received by the Radio for 2.5 s.
OBDII Code B127B 2018 GMC Sierra - Rearview Camera Input Signal Circuit - AutoCodes.com
B127B 2018 GMC Sierra Code - Rearview Camera Input Signal Circuit
What does this mean?

What are the Possible Causes of the DTC B127B 2018 GMC Sierra?

  • Faulty Rearview Camera
  • Rearview Camera harness is open or shorted
  • Rearview Camera circuit poor electrical connection
  • Faulty Human Machine Interface Control Module
  • Faulty Info Display Module

How to Fix the DTC B127B 2018 GMC Sierra?

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

A poor video image can be caused by ice, snow, and mud buildup on the lens of the Rearview Camera. Also, extreme lighting conditions can affect performance, such as operating in the dark or with bright sunlight shining on the camera. Extreme high or low temperatures can also affect image quality. An open or high resistance in the shield of the video signal circuit can also cause a distorted screen.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B127B 2018 GMC Sierra 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 B127B 2018 GMC Sierra code?

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Need Help with the 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 B127B 2018 GMC Sierra Code

1. What does OBDII code B127B mean on a 2018 GMC Sierra?

Code B127B indicates an issue with the rearview camera input signal circuit, meaning the system is not receiving or processing the camera's signal correctly.

2. What are common symptoms of the B127B code?

The most common symptoms include a blank or distorted rearview camera display, intermittent video feed, or no image on the infotainment screen when in reverse.

3. What causes code B127B to appear on a 2018 GMC Sierra?

This code can be caused by a faulty rearview camera, damaged wiring or connectors, a malfunctioning infotainment system, or a software issue.

4. Can a bad rearview camera trigger the B127B code?

Yes, a defective rearview camera is a common cause of this code as it prevents the input signal from being properly transmitted to the display system.

5. How can I diagnose the B127B code?

Start by inspecting the rearview camera and its wiring for damage, corrosion, or loose connections. Use a scan tool to test the camera's signal and verify the code.

6. Is the B127B code a serious issue?

While it doesn’t affect vehicle drivability, it compromises rear visibility, which may pose a safety risk when reversing.

7. How do I fix the B127B code on a 2018 GMC Sierra?

Fixes may include repairing or replacing damaged wires or connectors, replacing the rearview camera, or reprogramming the infotainment system.

8. Can software updates resolve the B127B code?

In some cases, a software update for the infotainment system can resolve the issue, especially if it’s caused by a system glitch.

9. How much does it cost to repair the B127B code?

Repair costs vary but may range from $100 to $500, depending on whether the camera or other components need replacement.

10. Can I drive with the B127B code active on my GMC Sierra?

Yes, you can drive, but the rearview camera may not function, so extra caution is needed when reversing.

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