The B1905 diagnostic trouble code (DTC) indicates a problem within the supplemental restraint system (SRS), specifically related to the second crash sensor's feed and return circuit. This means the airbag control module (ACM) has detected an unintended voltage presence on the circuit, signaling a "short to battery" condition. Addressing this promptly is crucial for ensuring the airbags deploy correctly in the event of a collision, protecting vehicle occupants.
The B1905 code does not necessarily mean the airbag will deploy spontaneously. It indicates a problem with the sensor's monitoring circuit, which can prevent proper airbag deployment during an accident. Therefore, diagnosis and repair are essential for safety.
| Topic | Description | Possible Causes |
|---|---|---|
| Definition of B1905 | Air Bag Crash Sensor #2 Feed/Return Circuit Short To Battery. This means the ACM has detected a higher than expected voltage on the circuit for the sensor. | Damaged wiring harness, faulty crash sensor #2, corroded connectors, internal fault within the ACM (rare), chafing wires leading to a short against a positive voltage source. |
| Location of Crash Sensor #2 | Varies depending on vehicle make and model. Commonly located in the front of the vehicle, either behind the bumper, near the headlights, or within the engine compartment, but can also be located within the passenger compartment. Consult your vehicle's repair manual. | Incorrectly identified sensor, damaged wiring during collision repair near the sensor's location. |
| Function of Crash Sensor #2 | Detects sudden deceleration indicating a collision. Sends a signal to the ACM. These sensors are often accelerometers, measuring changes in velocity. They work in conjunction with other sensors to determine the severity of a crash. | Sensor failure due to impact damage (even minor), internal sensor malfunction due to age or environmental factors (moisture, heat). |
| Feed/Return Circuit Explained | A circuit with two wires: a 'feed' wire supplying voltage to the sensor and a 'return' wire providing a path for the current back to the ACM. This closed loop allows the ACM to continuously monitor the sensor's status. | Damaged wires creating a short to a 12V source, corroded connectors increasing resistance and affecting voltage readings. |
| Symptoms Associated with B1905 | Airbag warning light illuminated on the dashboard. Potentially disabled airbags. In some vehicles, other SRS features might be disabled. The code itself is the primary symptom. | Ignoring the warning light, continuing to drive with potentially non-functional airbags. |
| Diagnostic Tools Required | OBD-II scanner capable of reading SRS codes, multimeter, wiring diagrams specific to the vehicle make and model, possibly a breakout box for accessing the ACM connectors. | Relying on generic OBD-II scanners that don't read SRS codes, attempting repairs without wiring diagrams. |
| Common Wiring Issues | Chafing against metal components, rodent damage, corrosion at connectors, damaged wiring from previous repairs, broken wires within the harness. | Ignoring visual inspection of wiring, failing to properly repair wiring damage (using improper connectors or soldering techniques). |
| ACM (Airbag Control Module) Role | The "brain" of the SRS. Receives signals from crash sensors, determines if airbag deployment is necessary, and controls the deployment of airbags and seatbelt pretensioners. | ACM failure (rare), internal damage to the ACM preventing proper sensor monitoring. |
| Testing the Crash Sensor #2 | Using a multimeter to check the voltage and resistance of the feed and return circuits. Comparing readings to specifications in the vehicle's repair manual. Sometimes, a specialized tool is needed to simulate a crash event for testing. | Incorrectly interpreting multimeter readings, replacing the sensor without proper testing. |
| Potential Consequences of Ignoring B1905 | Airbags may not deploy in a collision, increasing the risk of injury. The SRS system might be completely disabled. | Increased risk of serious injury or death in an accident. |
| Repair Procedures | Inspect wiring harness for damage, repair or replace damaged wiring, clean corroded connectors, replace faulty crash sensor, test the circuit after repairs, clear the DTC. | Improper wiring repair, replacing parts without proper diagnosis, failing to clear the DTC after repairs. |
| Voltage Readings and Interpretation | A short to battery will show a voltage close to battery voltage (around 12V) on the return wire when it should be significantly lower. Compare to the factory service manual for specific values. | Misinterpreting voltage readings, assuming a faulty sensor without checking the wiring. |
| Resistance Readings and Interpretation | High resistance in the circuit can indicate corrosion or a broken wire. Very low resistance (close to zero) can indicate a short to ground. Compare to the factory service manual for specific values. | Misinterpreting resistance readings, assuming a faulty sensor without checking the wiring. |
| Importance of Wiring Diagrams | Wiring diagrams are essential for tracing the circuit, identifying connector locations, and understanding the wiring configuration. They are crucial for accurate diagnosis and repair. | Attempting repairs without wiring diagrams, potentially causing further damage. |
| Component Replacement Considerations | Always disconnect the battery before working on the SRS. Use only OEM or high-quality aftermarket parts. Follow the manufacturer's instructions for installation and calibration. | Using low-quality replacement parts, failing to disconnect the battery, improperly installing components. |
| Clearing the DTC | After completing repairs, use an OBD-II scanner to clear the B1905 DTC. Verify that the airbag warning light is no longer illuminated. | Failing to clear the DTC after repairs, the airbag warning light may remain on even if the problem is fixed. |
| Professional Assistance | If you are not comfortable working on the SRS, seek professional assistance from a qualified mechanic or automotive technician. The SRS is a safety-critical system and should be handled with care. | Attempting repairs beyond your skill level, potentially causing further damage or compromising safety. |
| Effect of Temperature on Resistance | Resistance of wires can increase with temperature. This effect is usually minimal but should be considered when taking measurements in extreme temperatures. | Ignoring the effect of temperature on resistance, potentially misinterpreting readings taken in extreme conditions. |
| Effect of Vibration on Connections | Vibration can loosen connections and cause intermittent faults. Inspect connectors for looseness and corrosion. | Ignoring the effect of vibration on connections, potentially overlooking intermittent faults. |
Detailed Explanations
Definition of B1905: This code points to an electrical fault where the airbag control module (ACM) is detecting excessive voltage (close to battery voltage) on the feed or return wire of the crash sensor #2 circuit. This indicates that the wire, or part of the circuit, is making unintended contact with a positive voltage source, typically the vehicle's battery voltage.
Location of Crash Sensor #2: The location of crash sensor #2 is vehicle-specific. It's crucial to consult the vehicle's repair manual or wiring diagrams to pinpoint its exact location. Common locations include the front bumper area, near the headlights, or within the engine compartment. Some vehicles may have it located within the passenger compartment.
Function of Crash Sensor #2: Crash sensor #2, like other crash sensors, is designed to detect sudden deceleration forces associated with a collision. It functions as an accelerometer, measuring changes in velocity. When a significant deceleration is detected, the sensor sends a signal to the ACM, which then evaluates the information from all sensors to determine if airbag deployment is necessary.
Feed/Return Circuit Explained: The feed/return circuit is a fundamental electrical circuit design. The 'feed' wire supplies power (voltage) to the crash sensor. The 'return' wire provides a path for the current to flow back to the ACM. This closed loop allows the ACM to constantly monitor the integrity and status of the sensor. Any interruption or abnormal voltage reading in this circuit triggers a diagnostic trouble code like B1905.
Symptoms Associated with B1905: The most obvious symptom is the illumination of the airbag warning light on the dashboard. More critically, the airbags may be disabled, meaning they will not deploy in the event of a collision. In some vehicles, other SRS-related features, such as seatbelt pretensioners, may also be deactivated.
Diagnostic Tools Required: Diagnosing B1905 requires specific tools. An OBD-II scanner capable of reading SRS codes is essential to confirm the code and access relevant data. A multimeter is needed to measure voltage and resistance in the circuit. Wiring diagrams specific to the vehicle are crucial for tracing the circuit and identifying components. A breakout box can be helpful for accessing the ACM connectors.
Common Wiring Issues: Wiring problems are a frequent cause of B1905. These can include chafing of wires against metal components, rodent damage to the wiring harness, corrosion at connectors, damaged wiring from previous repairs, and broken wires within the harness. Thorough visual inspection is critical.
ACM (Airbag Control Module) Role: The ACM acts as the central control unit for the entire SRS. It receives signals from the crash sensors, processes the information, and determines if airbag deployment is necessary. It also controls the deployment of airbags and seatbelt pretensioners. While ACM failure is relatively rare, it's a possibility.
Testing the Crash Sensor #2: Testing involves using a multimeter to measure the voltage and resistance on the feed and return circuits. Compare these readings to the specifications in the vehicle's repair manual. Some advanced diagnostic procedures may involve simulating a crash event with specialized tools.
Potential Consequences of Ignoring B1905: Ignoring B1905 carries significant safety risks. The airbags may fail to deploy in a collision, increasing the risk of serious injury or death. The entire SRS system might be disabled, leaving occupants unprotected.
Repair Procedures: Repairing B1905 involves several steps. First, inspect the wiring harness for any signs of damage. Repair or replace any damaged wiring. Clean corroded connectors. If the sensor is faulty, replace it. After repairs, thoroughly test the circuit to ensure the problem is resolved and clear the DTC using an OBD-II scanner.
Voltage Readings and Interpretation: In a short-to-battery situation, the return wire of the crash sensor circuit will typically exhibit a voltage close to battery voltage (around 12V) when it should normally be much lower. Comparing the actual readings with the values specified in the factory service manual is essential for accurate diagnosis.
Resistance Readings and Interpretation: High resistance in the circuit can indicate corrosion, a loose connection, or a broken wire. Conversely, very low resistance (close to zero) can indicate a short to ground. Again, consult the factory service manual for the correct resistance values for your specific vehicle.
Importance of Wiring Diagrams: Wiring diagrams are indispensable tools for diagnosing electrical issues like B1905. They provide a detailed map of the circuit, showing wire colors, connector locations, and component connections. Without a wiring diagram, tracing the circuit and identifying potential problems becomes significantly more difficult.
Component Replacement Considerations: When replacing components in the SRS, always disconnect the vehicle's battery to prevent accidental airbag deployment. Use only OEM (Original Equipment Manufacturer) or high-quality aftermarket parts that meet or exceed OEM specifications. Follow the manufacturer's instructions carefully for installation and calibration.
Clearing the DTC: After completing repairs, it's crucial to clear the B1905 DTC using an OBD-II scanner. This resets the SRS system and verifies that the airbag warning light is no longer illuminated. If the light remains on, it indicates that the problem has not been fully resolved.
Professional Assistance: The SRS is a safety-critical system, and repairs should only be performed by qualified individuals with the appropriate knowledge, skills, and tools. If you are not comfortable working on the SRS, seek professional assistance from a licensed mechanic or automotive technician.
Effect of Temperature on Resistance: The resistance of wires can slightly increase with temperature. While this effect is usually minimal, it should be considered when taking measurements in extreme temperatures. Allow components to reach ambient temperature before taking measurements for the most accurate results.
Effect of Vibration on Connections: Vibration can loosen electrical connections over time, leading to intermittent faults. When diagnosing B1905, carefully inspect connectors for looseness, corrosion, or damage. Ensure that all connections are secure and properly seated.
Frequently Asked Questions
What does the B1905 code mean? It means the airbag control module has detected a short to battery on the feed or return circuit of crash sensor #2.
Is it safe to drive with a B1905 code? It is not recommended, as your airbags may not deploy properly in a collision.
Can I fix the B1905 code myself? If you have experience with automotive electrical systems and access to the necessary tools, you may be able to diagnose and repair the problem. However, due to the safety-critical nature of the SRS, professional assistance is recommended.
How do I find the location of crash sensor #2? Consult your vehicle's repair manual or wiring diagrams for the specific location of the sensor.
What tools do I need to diagnose B1905? You will need an OBD-II scanner capable of reading SRS codes, a multimeter, and wiring diagrams.
Conclusion
The B1905 code indicates a serious problem within the SRS that requires prompt attention. Diagnosing and repairing this code correctly is crucial for ensuring the safety and functionality of your vehicle's airbags. Always prioritize safety and seek professional assistance if you are not comfortable performing the repairs yourself.