AutoCodes – GMC – U2120 GMC

U2120 GMC Code - Lost Communication With Dynamic Headlamp Leveling Device

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Dynamic Headlamp Leveling (DHL) Device, Dynamic Headlamp Leveling Device harness is open or shorted, Dynamic Headlamp Leveling Device 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: U2120 GMC indicates Lost Communication With Dynamic Headlamp Leveling Device.
Common causes: Common causes include Faulty Dynamic Headlamp Leveling (DHL) Device, Dynamic Headlamp Leveling Device harness is open or shorted, Dynamic Headlamp Leveling Device 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 494

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 Jun 16, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U2120 GMC Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. A loss of serial data communications Diagnostic Trouble Code (DTC) does not represent a failure of the devices that contain the stored code. The DTC will set when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U2120 GMC - Lost Communication With Dynamic Headlamp Leveling Device - AutoCodes.com — U2120 GMC Code - Lost Communication With Dynamic Headlamp Leveling Device

What does this mean?

What are the Possible Causes of the DTC U2120 GMC?

Faulty Dynamic Headlamp Leveling (DHL) Device
Dynamic Headlamp Leveling Device harness is open or shorted
Dynamic Headlamp Leveling Device circuit poor electrical connection

How to Fix the DTC U2120 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 U2120 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.

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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 U2120 GMC Code

1. What are the common symptoms of OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

The common symptoms include malfunctioning or erratic behavior of the dynamic headlamp leveling system, dashboard warning lights, and headlights pointing in the wrong direction.

2. What are the possible causes of OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

Possible causes include a faulty dynamic headlamp leveling device, damaged wiring or connectors, a blown fuse related to the system, or a communication error within the vehicle's network.

3. How can I diagnose the issue related to OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

You can diagnose the issue by inspecting the wiring and connectors related to the dynamic headlamp leveling system, checking the fuse, and using a diagnostic scanner to identify communication errors within the vehicle's network.

4. What are some repair tips for fixing OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

Repair tips include checking and replacing any damaged wiring or connectors, ensuring the fuse related to the system is in good condition, and reprogramming or replacing the dynamic headlamp leveling device if necessary.

5. Can I drive my vehicle with OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

It is not recommended to drive your vehicle with this code present, as it can affect the proper functioning of the dynamic headlamp leveling system, potentially leading to safety issues or failed inspections.

6. How much does it cost to repair OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

The cost of repair can vary depending on the specific cause of the issue. Simple fixes like replacing a fuse or repairing wiring may cost less, while replacing the dynamic headlamp leveling device can be more expensive.

7. Can OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device cause other problems in the vehicle?

While this code specifically relates to the communication issue with the dynamic headlamp leveling device, unresolved issues can potentially affect other systems connected to the vehicle's network, leading to further complications.

8. How long does it take to repair OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device?

The repair time can vary depending on the complexity of the issue and the availability of parts. Simple fixes may take a short amount of time, while more involved repairs could require more extensive troubleshooting.

9. Can I reset OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device without repairing the issue?

Resetting the code without fixing the underlying problem will only temporarily remove the warning light. It is important to diagnose and repair the issue to ensure proper functioning of the dynamic headlamp leveling system.

10. Is OBDII code U2120 (GMC) - Lost Communication With Dynamic Headlamp Leveling Device a common issue in GMC vehicles?

While not extremely common, issues related to lost communication with the dynamic headlamp leveling device can occur in GMC vehicles equipped with this system. Regular maintenance and inspection can help prevent such problems.