AutoCodes – GMC – B0984 GMC

B0984 GMC Code - Left Headlamp Light Distribution Shutter Control Circuit Malfunction

Quick Answer

Battery positive voltage is applied to the headlamp control module at all times. Common causes include Faulty Left Headlamp Assembly, Left Headlamp Assembly harness is open or shorted, Left Headlamp Assembly 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: B0984 GMC indicates Left Headlamp Light Distribution Shutter Control Circuit Malfunction.
Common causes: Common causes include Faulty Left Headlamp Assembly, Left Headlamp Assembly harness is open or shorted, Left Headlamp Assembly 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 1,109

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 Mar 11, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0984 GMC Description

Battery positive voltage is applied to the headlamp control module at all times. The headlamp control module has a normal operational voltage range of about 12.5-16 V and is only fully functional with the ignition switch is in the RUN position and the headlamp switch in the AUTO position. The communications enable signal from the Body Control Module (BCM) wakes the headlamp control module microprocessor. The headlamp control module receives serial data messages from the Engine Control Module (ECM), Transmission Control Module (TCM), Electronic Brake Control Module (EBCM), and BCM with information regarding power mode, speed, steering angle, transmission gear selection, and headlamp switch status. The headlamp control module calculates the headlamp angle and sends commands to the left and right adaptive forward lighting system headlamp actuators. The headlamp actuators drive the headlamps to the position commanded by the headlamp control module. The headlamp control module monitors the headlamp actuator motor control circuits for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a DTC will be stored in memory and the driver will be notified with a message displayed over the driver information center located on the instrument cluster.

OBDII Code B0984 GMC - Left Headlamp Light Distribution Shutter Control Circuit Malfunction - AutoCodes.com — B0984 GMC Code - Left Headlamp Light Distribution Shutter Control Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC B0984 GMC?

Faulty Left Headlamp Assembly
Left Headlamp Assembly harness is open or shorted
Left Headlamp Assembly circuit poor electrical connection

How to Fix the DTC B0984 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 B0984 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 B0984 GMC Code

1. What does the OBDII code B0984 GMC indicate?

The code B0984 GMC indicates that there is a malfunction in the left headlamp light distribution shutter control circuit, which is part of the headlamp's system that controls beam focusing and direction.

2. What are common symptoms of the B0984 GMC code?

Common symptoms include the left headlight having issues with adaptive lighting or automatic high beam functioning, reduced visibility at night, and possibly a warning light on the dashboard.

3. What could cause the B0984 GMC code to appear?

Possible causes include faulty or damaged wiring in the headlamp control circuit, a bad left headlamp assembly, issues with the headlamp control module, or a poor connection in the headlamp circuit.

4. How can I diagnose the B0984 GMC code?

Diagnosis should start with a visual inspection of the headlamp assembly and associated wiring for any signs of damage or wear. Use a multimeter to check for proper voltage in the headlamp control circuit. A scan tool may also be necessary to diagnose deeper electronic issues.

5. What are the steps to repair the B0984 GMC code?

Repair steps may include replacing damaged wires or connectors, replacing the faulty left headlamp assembly if it cannot be repaired, or replacing or reprogramming the headlamp control module if it is found to be defective.

6. Is it safe to drive with the B0984 GMC code active?

While you may be able to drive the vehicle, it is not recommended to do so at night or in poor visibility conditions as the left headlamp may not function properly, which can reduce your visibility and increase the risk of an accident.

7. Can I fix the B0984 GMC code myself?

If you have experience with automotive electrical systems, you may be able to address simple issues such as replacing wires or connectors. However, for module replacements or complex diagnostics, professional service is recommended.

8. How urgent is it to address the B0984 GMC code?

It is fairly urgent to address this issue, especially if the vehicle is used frequently at night or in low-light conditions, as the malfunctioning headlight can significantly impair visibility and safety.

9. What tools are needed to diagnose and repair the B0984 GMC code?

Tools needed may include a multimeter for electrical testing, a scan tool for diagnostic procedures, and basic hand tools for replacing components such as the headlamp assembly or wiring.

10. Could the B0984 GMC code impact other systems of the vehicle?

While the code specifically relates to the headlamp system, unresolved issues could potentially lead to broader electrical problems if caused by an underlying issue like a failing control module, impacting other electronically controlled systems.