AutoCodes – GMC – B3128 GMC

B3128 GMC Code - Left Front/Driver Door Unlock Circuit High

Quick Answer

The outputs to the door lock actuators are controlled by the Body Control Module (BCM). Common causes include Faulty Inoperative Door Lock Actuator, Inoperative Door Lock Actuator harness is open or shorted, Inoperative Door Lock Actuator 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: B3128 GMC indicates Left Front/Driver Door Unlock Circuit High.
Common causes: Common causes include Faulty Inoperative Door Lock Actuator, Inoperative Door Lock Actuator harness is open or shorted, Inoperative Door Lock Actuator 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 566

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 04, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B3128 GMC Description

The outputs to the door lock actuators are controlled by the Body Control Module (BCM). When the BCM receives a lock input from a door lock switch, or a keyless entry transmitter, it applies battery positive voltage to the door lock actuator lock control circuit, a ground to the door lock actuator unlock control, and the driver door lock actuator unlock control circuits. When the BCM receives an unlock input from a door lock switch, it applies battery positive voltage to the door lock actuator unlock control, the driver door lock actuator unlock control circuits, and a ground to the door lock actuator lock control circuit. When the BCM receives an single Unlock input from a keyless entry transmitter, it applies battery positive voltage to the driver door lock actuator unlock control circuit and a ground to the door lock actuator lock control circuit to unlock the driver door. A second Unlock input from the transmitter applies battery positive voltage to the door lock actuator unlock control circuit, and a ground to the door lock actuator lock control circuit to unlock the passenger doors.

OBDII Code B3128 GMC - Left Front/Driver Door Unlock Circuit High - AutoCodes.com — B3128 GMC Code - Left Front/Driver Door Unlock Circuit High

What does this mean?

What are the Possible Causes of the DTC B3128 GMC?

Faulty Inoperative Door Lock Actuator
Inoperative Door Lock Actuator harness is open or shorted
Inoperative Door Lock Actuator circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B3128 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 B3128 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 B3128 GMC Code

1. What are common symptoms of OBDII code B3128 GMC related to the Left Front/Driver Door Unlock Circuit High?

- Common symptoms include difficulty unlocking the left front/driver door using the key fob or interior door switch.

2. What can cause the OBDII code B3128 GMC Left Front/Driver Door Unlock Circuit High?

- Possible causes include a faulty door lock actuator, damaged wiring harness, or a malfunctioning door control module.

3. How can I diagnose the issue causing OBDII code B3128 GMC on the left front/driver door?

- Use a multimeter to test the continuity of the wiring harness, check the door lock actuator for proper function, and inspect the door control module for any signs of damage.

4. What are some repair tips for fixing OBDII code B3128 GMC related to the Left Front/Driver Door Unlock Circuit High?

- Start by checking and repairing any damaged wiring harness connections, then proceed to replace the door lock actuator or door control module if needed.

5. Can OBDII code B3128 GMC cause other electrical issues in the vehicle?

- While this code specifically relates to the left front/driver door unlock circuit, it can potentially lead to other electrical issues if left unresolved, affecting the overall functionality of the door system.

6. Is it safe to continue driving with the OBDII code B3128 GMC triggered?

- It is generally safe to drive with this code, but it is recommended to address the underlying issue promptly to avoid potential inconvenience or safety concerns related to door operation.

7. How much does it typically cost to repair OBDII code B3128 GMC on the left front/driver door?

- The cost of repair can vary depending on the specific cause of the issue, but it may range from $100 to $300 for parts and labor.

8. Can I reset the OBDII code B3128 GMC myself after repairing the left front/driver door issue?

- Yes, you can reset the code using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes to clear the stored error code.

9. Are there any preventive maintenance steps to avoid OBDII code B3128 GMC in the future?

- Regularly inspecting and maintaining the door lock components, such as lubricating the door lock mechanism, can help prevent issues that trigger this code.

10. Will fixing OBDII code B3128 GMC affect the vehicle's overall performance or fuel efficiency?

- Fixing this specific code is unlikely to have a direct impact on performance or fuel efficiency, but it is necessary for the proper functioning of the door unlocking system.