2018-2025 Honda Accord: Solving BSI System Problems & Replacing Rear Radar

Symptoms of a Failing Blind Spot Sensor

When a rear blind spot radar unit begins to fail on a 2018-2025 Honda Accord, the symptoms are usually very clear and consistent.

• "Blind Spot Information System Problem" Message: This is the most common symptom. A warning message will appear on the driver information interface, and the entire BSI system will be disabled.
• BSI and Cross Traffic Monitor Inoperative: The indicator lights on the side mirrors will not illuminate when cars are in your blind spot, and you will not receive audible alerts when using your turn signal. The Cross Traffic Monitor will also fail to provide warnings when reversing.
• System Can't Be Turned On: If you try to enable the system through the vehicle's settings menu on the infotainment screen, the option may be grayed out or immediately return to an 'Off' or error state.
• Intermittent Failure: In the early stages of failure, the system might work sporadically. It may fail after a car wash or during heavy rain, and then begin working again once it dries out. This often points to a cracked sensor housing or a failing seal allowing moisture inside.
• Diagnostic Trouble Codes (DTCs): A professional scan tool can pull specific codes from the BSI module. A common code is U1297, which indicates a loss of communication between the left and right radar units, often because one unit has failed and is no longer communicating on the vehicle's network. Other codes may point to an internal failure of a specific sensor.

Common Causes of Failure

These radar units are sophisticated electronic devices placed in a vulnerable location. Failure is typically caused by one of two things:

1. Physical Impact: Even a minor bump to the rear bumper corner can damage the sensor or its mounting bracket. The owner's manual advises having the system checked by a dealer any time the rear bumper is impacted.
2. Water Intrusion: The sensors are sealed, but over time these seals can degrade. Cracks in the plastic housing from road debris or stress can allow water inside, shorting out the electronics. This is a very common failure mode reported by owners.

Buying a Used Collision Avoidance Sensor

Due to the high cost of new OEM sensors, a quality used OEM unit is often the best value. However, you must be careful when purchasing one to ensure compatibility and function.

What to Inspect

• Housing Integrity: Carefully inspect the entire plastic housing of the sensor. Look for any cracks, especially along the seams where the front and back halves are joined. A cracked housing means it is no longer water-tight and should be avoided.
• Connector Pins: Look inside the electrical connector. The pins should be straight, clean, and free of any green or white corrosion. Corroded pins indicate moisture has already gotten into the unit.
• Mounting Points: Ensure all mounting tabs are intact and not cracked or broken. A sensor that cannot be mounted securely will not function correctly.
• Part Number Match: This is critical. You must match the OEM part number exactly. While sensors may look identical, they can have different software versions. Using a sensor with the wrong software can cause communication errors (DTCs B18DA or B1EDA) and prevent the system from working. Be aware that there are different part numbers for the left (driver) and right (passenger) sides.

Why Used OEM is a Good Choice

For complex electronics like radar sensors, OEM parts are generally superior to aftermarket alternatives. Aftermarket options for this specific part are rare or non-existent. A used OEM sensor that has been properly inspected offers the same performance and reliability as a new one at a fraction of the price.

Replacement and Calibration

Replacing a rear radar sensor is a moderately difficult job, primarily because it requires removing the rear bumper cover.

Installation Steps Overview:

1. Disconnect the negative battery terminal.
2. Remove the screws and clips securing the rear bumper cover in the wheel wells, underneath the vehicle, and in the trunk area.
3. Carefully unsnap the bumper cover from the retaining brackets below the taillights and pull it away from the vehicle. If you have parking sensors, disconnect their harness before fully removing the bumper.
4. Locate the failed radar unit, which is bolted to a bracket in the corner of the vehicle.
5. Disconnect the electrical connector and remove the bolts holding the sensor to its bracket.
6. Install the replacement sensor, ensuring it is seated correctly on its bracket.
7. Reconnect the electrical connector and reinstall the bumper cover by reversing the removal steps.

Known Issues, Recalls, and TSBs

As of late 2025, there are no specific recalls for the Blind Spot Information (BSI) system on 2018-2025 Honda Accords. However, there was a recall for 2018-2020 models (NHTSA ID: 20V-771) related to a software error in the Body Control Module (BCM) that could disrupt communication with various components, potentially affecting systems like exterior lights and the rearview camera. While not directly targeting the BSI sensors, it highlights the sensitivity of the vehicle's communication networks. Widespread owner reports in online forums confirm that sensor failure is a common issue, but it has not led to a formal recall.

Part Number Reference

This list contains known OEM part numbers for the rear BSI radar units. Always verify the part number from your original sensor before ordering a replacement. Part numbers can be superseded over time.

• Right (Passenger Side): 36930-TVA-A01, 36931-TVA-A01, 36931TVAA01, 36931TVAA02
• Left (Driver Side): 36935-TVA-A01, 36936-TVA-A01, 36936-TVA-A11, 36936-TVA-A12
• Other Related Numbers: 8S410-30A, 8S410-30A-A02, 8S410-30A-A10, 8S410-3A0-K91, 8S411-30A-A02, 8S411-30A-A11, 8S411-3A0-K91, 8S411-3A0-A21

Frequently Asked Questions (FAQ)