B2120 – OBD-II DTC

OBD-II DTC B2120 – Door Passenger Set Switch Stuck Failure

DTC B2120 meaning

DTC B2120 refers to a diagnostic trouble code indicating a “Door Passenger Set Switch Stuck Failure.” This code is generated when the vehicle’s onboard diagnostic system detects that the passenger door set switch is not functioning correctly, typically remaining in a stuck position. This can affect the operation of various electrical components associated with the passenger door, such as window controls and door locks.

DTC B2120 symptoms

Common symptoms associated with DTC B2120 may include:

• Inability to operate the passenger door window.
• Passenger door lock not functioning.
• Warning lights illuminated on the dashboard.
• Intermittent or complete failure of the passenger door switch.
• Unusual noises from the door area when attempting to operate the switch.

DTC B2120 causes

Several factors can lead to the occurrence of DTC B2120, including:

• Faulty passenger door set switch.
• Wiring issues, such as shorts or open circuits in the switch harness.
• Corrosion or dirt buildup affecting the switch’s operation.
• Faulty body control module (BCM) that misinterprets the switch’s status.
• Mechanical failure within the door assembly that prevents the switch from functioning properly.

DTC B2120 seriousness

The seriousness of DTC B2120 can vary based on the symptoms experienced. While it may not pose an immediate safety risk, it can lead to inconvenience due to inoperable door functions. If left unaddressed, it may result in further electrical issues or damage to the vehicle’s electrical system. Therefore, it is advisable to diagnose and repair the issue promptly.

How to diagnose DTC B2120

To diagnose DTC B2120, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B2120.
2. Inspect the passenger door set switch for visible damage or wear.
3. Check the wiring and connectors associated with the switch for signs of corrosion or damage.
4. Test the switch’s functionality using a multimeter to ensure it operates correctly.
5. Examine the body control module for any faults or error codes that may relate to the switch.
6. Perform a continuity test on the wiring harness to ensure there are no breaks or shorts.

How to fix DTC B2120 step-by-step instructions

To fix DTC B2120, follow these step-by-step instructions:

1. Disconnect the vehicle’s battery to ensure safety while working on electrical components.
2. Remove the passenger door panel to access the door set switch.
3. Inspect the switch for any visible damage and replace it if necessary.
4. Check the wiring harness for any signs of wear, corrosion, or damage, and repair or replace as needed.
5. Reconnect any loose or damaged connectors to ensure proper electrical contact.
6. Reassemble the door panel and reconnect the vehicle’s battery.
7. Clear the DTC using an OBD-II scanner and test the passenger door functions to ensure proper operation.

How to erase DTC B2120

To erase DTC B2120, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the vehicle’s ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear DTCs” option on the scanner.
4. Confirm the action to clear the trouble codes from the vehicle’s memory.
5. Disconnect the scanner and start the vehicle to ensure the code does not reappear.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.