B0104 is a body-related diagnostic trouble code (DTC) associated with the vehicle's Supplemental Restraint System (SRS). On many General Motors applications, B0104 identifies a fault involving the Electronic Front End Sensor 2, commonly associated with the passenger/right side of the vehicle.
The exact definition of B0104 is not universal across every manufacturer. Some vehicles may assign a different SRS or airbag circuit description to the same code. Always confirm the exact DTC description displayed by the SRS control module and the manufacturer's service information before replacing a component.
B0104 Code Description
System: Supplemental Restraint System (SRS)
Responsible component on many GM applications: Electronic Front End Sensor 2
Module: Sensing and Diagnostic Module (SDM) or equivalent SRS control module
On many GM vehicles, the front impact sensor communicates with the SRS control module through a dedicated two-wire circuit. The SDM supplies the sensor and monitors its identification and status information. If the module detects repeated invalid or NOK (Not OK) messages from the sensor, it can store B0104.
OEM / Manufacturer-Specific Meaning
B0104 should not be treated as a universal description across every vehicle make.
For example, GM service information identifies B0104 as a fault involving Electronic Front End Sensor 2. On some GM applications this is the right/passenger-side front sensor. The exact wording and sensor designation depend on the vehicle.
Other manufacturers may use B0104 for a different SRS circuit or component. Therefore, the safest diagnostic approach is to identify the vehicle make, model, year, SRS module and exact DTC description before beginning repairs.
Common Causes of B0104
- Faulty Electronic Front End Sensor 2.
- Damaged front impact sensor wiring.
- Corroded or loose sensor connector.
- Water intrusion around the sensor or connector.
- Physical damage to the front impact sensor.
- Open circuit in the sensor communication circuit.
- Short circuit or abnormal electrical condition in the sensor circuit.
- Incorrect or incompatible replacement sensor.
- Previous collision damage affecting the sensor mounting area.
- Low system voltage or an electrical problem affecting SRS operation.
- Fault in the SRS/SDM control module.
On GM systems, the SDM monitors the front-end sensor communication and can set B0104 when the expected sensor status or identification is not received correctly.
Symptoms of B0104
- SRS or Airbag warning light illuminated.
- Service Airbag warning message.
- B0104 stored in the SRS control module.
- Additional SRS or front-impact-sensor codes may be present.
- The airbag system may not operate as intended during a collision.
- The fault may remain active after the vehicle is restarted.
The exact symptoms depend on the vehicle and whether the fault is currently active or stored as an intermittent condition.
Is B0104 Serious?
Yes. B0104 should be treated as a safety-related fault.
Because the code can involve the SRS and front impact sensing system, it should not be ignored. A fault in an airbag sensing system can affect the system's ability to correctly detect or respond to a collision.
If the SRS warning light is illuminated, do not assume that the airbags will operate normally simply because the vehicle drives normally.
Can You Drive With B0104?
The vehicle may continue to operate mechanically with B0104, but normal engine operation does not mean that the SRS system is functioning correctly.
Because this is a safety-system fault, the vehicle should be diagnosed as soon as practical. Avoid unnecessary driving until the SRS system has been properly inspected, especially if the airbag warning light remains illuminated.
Where Is the B0104 Sensor Located?
On many GM applications where B0104 identifies Electronic Front End Sensor 2, the sensor is mounted toward the front of the vehicle, commonly around the radiator support, front structural area or another location specified by the manufacturer.
The exact position varies by vehicle. Do not use a generic sensor location when working on an SRS system. Consult the service information for the exact year, model and body configuration.
Which Part Is Responsible for B0104?
Electronic Front End Sensor 2 (Front Impact Sensor 2)
This sensor communicates with the SRS control module and provides information used by the restraint system to evaluate the vehicle's impact-sensing status.
However, B0104 does not automatically prove that the sensor itself has failed. Wiring, connectors, communication circuits, mounting damage and the SRS control module must also be considered.
How to Fix B0104
1. Confirm the Exact B0104 Definition
Use an SRS-capable diagnostic scanner and identify the module that stored the code. Confirm the exact description rather than relying only on a generic online DTC database.
2. Check for Additional SRS Codes
Record all active, stored and history codes before clearing anything. Related SRS codes can provide important information about the location of the fault.
3. Inspect the Front Impact Sensor
Visually inspect the suspected Electronic Front End Sensor 2 for physical damage, corrosion, water intrusion, damaged mounting hardware or evidence of a previous collision.
4. Inspect the Wiring and Connector
Check the wiring leading to the sensor for cuts, crushed sections, corrosion, loose terminals or collision-related damage.
Do not back-probe or electrically test SRS circuits using procedures that are not specifically approved by the manufacturer.
5. Verify Sensor Identification and Communication
On systems such as GM's electronic front-end sensor network, the SRS module expects the sensor to provide valid identification and status information. A communication or sensor-identification problem can therefore cause a DTC even when the sensor does not have obvious external damage.
6. Check Manufacturer Service Information
Follow the exact diagnostic procedure for the vehicle. The required tests, connector identification, sensor replacement procedure and SRS reset procedure can vary significantly between manufacturers.
7. Replace the Sensor Only When Confirmed
If testing confirms that the Electronic Front End Sensor 2 is defective, replace it with the correct component specified for the vehicle.
8. Clear the SRS Code and Verify the Repair
After the underlying problem has been repaired, use an appropriate SRS-capable scan tool to clear the code and perform the required system self-test or verification procedure.
B0104 Diagnostic Signal Flow
↓
Sensor Power / Ground
↓
Electronic Front End Sensor 2
↓
Sensor Identification & Status Communication
↓
SRS Module Monitoring
↓
B0104 Stored if the expected sensor response is not valid
The exact circuit architecture can vary by manufacturer. Some systems use a dedicated communication method between the front impact sensor and SRS module rather than a conventional analog impact-sensor signal.
Common Repair Mistakes
Replacing the Sensor Without Checking the Wiring
A damaged connector or harness can produce symptoms similar to a failed sensor.
Using the Wrong Sensor
Front impact sensors can be application-specific. An incorrect sensor may communicate incorrectly or fail the SRS module's identification checks.
Ignoring Previous Collision Damage
A vehicle that has previously been involved in an accident may have hidden wiring, connector, mounting or structural damage around the front sensing area.
Using a Generic Engine Scanner
Basic engine code readers may not communicate with the SRS module. Use an SRS-capable diagnostic tool.
Testing Airbag Circuits With an Ohmmeter
Do not improvise electrical tests on airbag squib or igniter circuits. Follow the manufacturer's approved SRS diagnostic procedure and use the specified equipment.
Clearing the Code Without Repairing the Cause
Clearing B0104 without correcting the underlying fault can cause the code and SRS warning light to return.
B0104 Repair Cost
Approximately $50–$150+ depending on the shop and vehicle.
Approximately $50–$250+ depending on accessibility and damage.
Approximately $100–$400+ depending on vehicle and part.
Can cost considerably more if module replacement, programming or additional repairs are required.
These are general estimates rather than fixed prices. Actual cost depends on the vehicle, sensor type, labor rate, parts availability, previous collision damage and whether additional SRS repairs are required.
B0104 Diagnosis With an OBD2 Scanner
A standard generic OBD2 scanner may not be sufficient for B0104 because the fault can be stored in the SRS control module rather than the engine control module.
An appropriate diagnostic scanner should be capable of communicating with the vehicle's SRS/airbag system and displaying the manufacturer's available diagnostic information.
Before clearing the code, record the exact description, module, status and any accompanying SRS codes.
What B0104 Does Not Automatically Mean
- It does not automatically mean the airbag itself has failed.
- It does not automatically prove that the front impact sensor is defective.
- It does not automatically mean the SRS control module has failed.
- It does not have one identical definition on every vehicle.
- It should not be diagnosed by replacing parts based only on the code number.
Related B0104 Codes
Electronic Front End Sensor 1 performance fault on applicable GM systems.
Electronic Front End Sensor 1 fault on applicable GM systems.
Incorrect Electronic Front End Sensor 1 installed on applicable GM systems.
Electronic Front End Sensor 2 performance fault on applicable GM systems.
Incorrect Electronic Front End Sensor 2 installed on applicable GM systems.
These related codes are included only to help distinguish nearby SRS diagnostic codes. Their exact descriptions should always be verified against the vehicle-specific service information.
FAQ About B0104
What does B0104 mean?
B0104 is an SRS/body diagnostic code whose exact meaning depends on the manufacturer. On many GM vehicles, it identifies a fault involving Electronic Front End Sensor 2.
What part causes B0104?
On applicable GM vehicles, the primary component associated with B0104 is the Electronic Front End Sensor 2. However, wiring, connectors, communication problems or the SRS module can also cause the code.
Where is the B0104 sensor located?
On many GM vehicles, the front-end sensor is installed in the front structural or radiator-support area. The exact location varies by vehicle and should be confirmed using the service manual.
Can I drive with B0104?
The vehicle may drive normally, but an SRS fault should not be ignored. The airbag system may not function as intended during a collision, so the fault should be diagnosed promptly.
Can a bad connector cause B0104?
Yes. Corrosion, loose terminals, damaged wiring or poor electrical connections can interfere with communication between the front impact sensor and SRS module.
Does B0104 always mean the sensor is bad?
No. The sensor is only one possible cause. The complete circuit, connector, wiring, sensor identification and SRS control module should be evaluated before replacing parts.
Can a normal OBD2 scanner read B0104?
Not necessarily. Because B0104 can be stored in the SRS module, an SRS-capable diagnostic scanner may be required.
Is B0104 the same on every car?
No. B0104 is not safe to interpret from the code number alone across every manufacturer. The exact DTC description and diagnostic procedure can differ between vehicle makes and SRS systems.
Final Takeaway
B0104 is an SRS-related diagnostic code that, on many GM applications, points to a fault involving the Electronic Front End Sensor 2. The fault can result from the sensor itself, wiring, connectors, communication problems, previous collision damage or an SRS control-module issue.
The correct approach is to identify the exact vehicle-specific definition, scan the SRS module, inspect the relevant sensor and wiring, follow the manufacturer's SRS safety procedures and replace the responsible component only after the fault has been confirmed.