AutoCodes – Chevrolet – U1521 Chevrolet

U1521 Chevrolet Code - Headlamp Control Module/Headlamp Leveling Control Module Lost Communication With Left Headlamp On LIN Bus

Quick Answer

The Local Interconnect Network (LIN) Bus consists of a single wire with a transmission rate of 10.417 Kbit/s. Common causes include Faulty Left Headlamp, Left Headlamp harness is open or shorted, Left Headlamp 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: U1521 Chevrolet indicates Headlamp Control Module/Headlamp Leveling Control Module Lost Communication With Left Headlamp On LIN Bus.
Common causes: Common causes include Faulty Left Headlamp, Left Headlamp harness is open or shorted, Left Headlamp 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 1,055

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 03, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code U1521 Chevrolet Description

The Local Interconnect Network (LIN) Bus consists of a single wire with a transmission rate of 10.417 Kbit/s. The serial data is transmitted over a LIN circuit between a master control module and other LIN devices within a particular subsystem. If serial data communication is lost between any of the LIN devices on the LIN bus network, the master control module will set a no communication code against the non-communicating LIN device. The Diagnostic Trouble Code (DTC) will set when a supervised periodic message to the Headlamp Control Module/Headlamp Leveling Control Module from the Left Headlamp has not been received.

OBDII Code U1521 Chevrolet - Headlamp Control Module/Headlamp Leveling Control Module Lost Communication With Left Headlamp On LIN Bus - AutoCodes.com — U1521 Chevrolet Code - Headlamp Control Module/Headlamp Leveling Control Module Lost Communication With Left Headlamp On LIN Bus

What does this mean?

What are the Possible Causes of the DTC U1521 Chevrolet?

Faulty Left Headlamp
Left Headlamp harness is open or shorted
Left Headlamp circuit poor electrical connection
Faulty Headlamp Control Module/Headlamp Leveling Control Module

How to Fix the DTC U1521 Chevrolet?

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 U1521 Chevrolet 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 U1521 Chevrolet code?

Need more information on how to fix the U1521 Chevrolet code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1521 Chevrolet code diagnosed by a professional: Find a repair shop in your area

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 U1521 Chevrolet Code

1. What are the common symptoms of OBDII code U1521 in a Chevrolet related to the Headlamp Control Module?

- Common symptoms include the left headlamp not functioning properly, headlamp leveling issues, and dashboard warning lights related to the headlamp system.

2. What could cause the Headlamp Control Module to lose communication with the left headlamp on the LIN bus in a Chevrolet?

- Possible causes include a faulty headlamp control module, damaged wiring or connectors, a software issue, or a malfunction in the LIN communication network.

3. How can I diagnose the U1521 code related to the Headlamp Control Module in my Chevrolet?

- Diagnosing this code involves using a diagnostic scanner to retrieve the trouble codes, checking the wiring and connectors for any damage, and testing the headlamp control module and LIN bus communication.

4. Is it safe to drive my Chevrolet with the U1521 code indicating a communication issue with the left headlamp control module?

- Driving with this issue may affect headlamp functionality and visibility, so it is recommended to address the problem promptly to ensure proper operation of the headlamp system.

5. Can I reset the U1521 code related to the Headlamp Control Module myself in a Chevrolet?

- While you can clear the code using a diagnostic scanner, it is important to diagnose and repair the underlying issue causing the communication loss to prevent the code from reappearing.

6. What are some repair tips for resolving the U1521 code in a Chevrolet due to a lost communication with the left headlamp control module?

- Repair tips include checking and repairing any damaged wiring or connectors, ensuring the headlamp control module is functioning correctly, and updating software as needed.

7. Does the U1521 code in a Chevrolet always require replacing the Headlamp Control Module?

- Not necessarily. Sometimes the issue can be resolved by repairing damaged wiring, connectors, or addressing software glitches before considering module replacement.

8. Are there any recalls or technical service bulletins related to the U1521 code in Chevrolet vehicles?

- It's recommended to check with Chevrolet dealerships or online resources for any recalls or technical service bulletins specific to the U1521 code and headlamp control module issues.

9. Can extreme weather conditions or water exposure cause the U1521 code in a Chevrolet related to the Headlamp Control Module?

- Yes, extreme weather conditions or water exposure can potentially damage the headlamp control module, wiring, or connectors, leading to communication issues and triggering the U1521 code.

10. How much should I expect to pay for repairing the U1521 code in a Chevrolet caused by a lost communication with the left headlamp control module?

- Repair costs can vary depending on the exact cause of the issue, but it's advisable to consult with a professional mechanic for an accurate diagnosis and cost estimate.