AutoCodes – GMC – B2645 2018 GMC Sierra

B2645 2018 GMC Sierra Code - Ambient Light Sensor Circuit

Quick Answer

The ambient light sensor is used to monitor outside lighting conditions. Common causes include Faulty Ambient Light/Sunload Sensor, Ambient Light/Sunload Sensor harness is open or shorted, Ambient Light/Sunload Sensor circuit poor electrical connection. 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: B2645 2018 GMC Sierra indicates Ambient Light Sensor Circuit.
Common causes: Common causes include Faulty Ambient Light/Sunload Sensor, Ambient Light/Sunload Sensor harness is open or shorted, Ambient Light/Sunload Sensor circuit poor electrical connection.
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 175

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 29, 2023

Description
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
FAQs
Comments
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Code B2645 2018 GMC Sierra Description

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 V depending on outside lighting conditions. The Body Control Module (BCM) provides a 5 V reference signal to the ambient light sensor and the Heating, Ventilation, and Air Conditioning (HVAC) control module provides a low reference ground. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either Daytime Running Lights (DRL) or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the daytime running lamps ON. During low light conditions, the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel daytime running lamps operation.

OBDII Code B2645 2018 GMC Sierra - Ambient Light Sensor Circuit - AutoCodes.com — B2645 2018 GMC Sierra Code - Ambient Light Sensor Circuit

What does this mean?

What are the Possible Causes of the DTC B2645 2018 GMC Sierra?

Faulty Ambient Light/Sunload Sensor
Ambient Light/Sunload Sensor harness is open or shorted
Ambient Light/Sunload Sensor circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B2645 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

User Submitted Video

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B2645 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.

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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 B2645 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code B2645 (Ambient Light Sensor Circuit) in a 2018 GMC Sierra?

The common symptoms include issues with the automatic headlight control system, erratic behavior of interior lighting, and possible warning messages on the dashboard related to ambient light sensing.

2. What are the possible causes of OBDII code B2645 in a 2018 GMC Sierra?

The code B2645 can be triggered by a malfunctioning ambient light sensor, wiring or connector issues in the sensor circuit, or faults in the body control module (BCM) that controls the sensor.

3. How can I diagnose the ambient light sensor circuit issue in my 2018 GMC Sierra?

Diagnosing the issue involves checking the ambient light sensor for physical damage or blockage, inspecting the wiring and connectors for any signs of wear or corrosion, and using a diagnostic tool to read the BCM's sensor data.

4. Can I repair the ambient light sensor circuit issue in my 2018 GMC Sierra myself?

Depending on your skill level, you may be able to address the issue yourself by replacing the ambient light sensor, fixing wiring or connector problems, or resetting the BCM. However, if you're unsure, it's best to seek professional help.

5. Is it safe to continue driving my 2018 GMC Sierra with OBDII code B2645 present?

While the code B2645 may not directly affect the drivability of your vehicle, it's important to address the underlying issue promptly to ensure proper functioning of the ambient light sensor and related systems in your Sierra.

6. How much does it typically cost to repair OBDII code B2645 in a 2018 GMC Sierra?

The cost of repairing OBDII code B2645 can vary depending on the exact cause of the issue. Costs may include parts such as a new ambient light sensor or wiring harness, as well as labor charges if you choose to have a professional mechanic fix the problem.

7. Can extreme weather conditions impact the ambient light sensor circuit in a 2018 GMC Sierra?

Yes, extreme weather conditions such as heavy rain, snow, or intense sunlight can potentially affect the performance of the ambient light sensor and contribute to triggering OBDII code B2645.

8. Will resetting the OBDII code B2645 in my 2018 GMC Sierra make it go away permanently?

Resetting the code may temporarily clear it from the system, but if the underlying issue with the ambient light sensor circuit is not addressed, the code is likely to reappear once the problem resurfaces.

9. Are there any recalls or technical service bulletins related to OBDII code B2645 in a 2018 GMC Sierra?

It's advisable to check with a GMC dealership or visit the National Highway Traffic Safety Administration (NHTSA) website to see if there are any relevant recalls or technical service bulletins related to OBDII code B2645 for your specific vehicle.

10. How important is the ambient light sensor for the overall functionality of my 2018 GMC Sierra?

The ambient light sensor plays a crucial role in automatic lighting control and other comfort features of your vehicle. While not essential for basic operation, a malfunctioning sensor can impact convenience, safety, and overall driving experience.