AutoCodes – Generic – U2120

U2120 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 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 1,782

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

What does this mean?

What are the Possible Causes of the DTC U2120?

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?

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 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 U2120 code?

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Need Help with the Code?

Get the U2120 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U2120 Buick — Lost Communication With Dynamic Headlamp Leveling Device
U2120 Cadillac — Lost Communication With Dynamic Headlamp Leveling Device
U2120 Chevrolet — Lost Communication With Dynamic Headlamp Leveling Device
U2120 GMC — Lost Communication With Dynamic Headlamp Leveling Device

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 Code

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

- Common symptoms include malfunctioning automatic headlight leveling system, dim or misaligned headlights, and dashboard warning lights related to headlight leveling.

2. What are some possible causes of OBDII code U2120?

- Possible causes may include a faulty headlamp leveling device, damaged wiring or connectors, a blown fuse related to the system, or a malfunctioning control module.

3. How can I diagnose the issue related to OBDII code U2120?

- Diagnosis typically involves checking the headlamp leveling system components, inspecting wiring for damage, testing connectors for proper connection, and using a scan tool to retrieve additional fault codes.

4. Is it safe to drive with OBDII code U2120 illuminated?

- It is generally safe to drive with this code, but it is important to address the issue promptly to ensure proper functioning of the headlight leveling system for optimal visibility and safety.

5. How can I reset OBDII code U2120?

- The code can be reset using an OBDII scanner by clearing the fault codes stored in the vehicle's computer after addressing the underlying issue with the headlamp leveling system.

6. Can a DIY enthusiast repair OBDII code U2120 at home?

- DIY repairs are possible if the issue is related to a simple wiring or connector problem. However, more complex issues may require professional diagnosis and repair to ensure proper functioning of the headlamp leveling system.

7. What are some tips for preventing OBDII code U2120 from recurring?

- Regularly inspecting the headlamp leveling system components, keeping wiring connections secure, and addressing any issues promptly can help prevent the code from recurring.

8. Will fixing OBDII code U2120 improve my vehicle's performance?

- Fixing this code will primarily restore proper functioning of the headlamp leveling system, ensuring optimal visibility and safety while driving at night or in low-light conditions.

9. How long does it typically take to repair OBDII code U2120?

- The repair time can vary depending on the underlying cause of the code. Simple fixes like reconnecting a loose wire may take a short time, while replacing a faulty component or module may require more time.

10. Is it necessary to visit a dealership for repairs related to OBDII code U2120?

- While a dealership may have specialized knowledge and tools for repairing this code, independent repair shops or DIY enthusiasts with the right skills and equipment can also effectively address the issue.