The B1899 diagnostic trouble code (DTC) indicates a problem within the microphone input signal circuit, specifically an open circuit. This usually means the vehicle's computer (often the Body Control Module or BCM) isn't receiving the expected signal from the microphone, impacting features like hands-free calling, voice commands, or active noise cancellation. Diagnosing and resolving this issue is crucial for restoring full functionality of these systems and ensuring clear communication.
The B1899 error is often related to issues with the microphone itself, the wiring connecting the microphone to the vehicle's computer, or the computer itself. Identifying the root cause requires a systematic approach, starting with simple checks and progressing to more complex diagnostic procedures.
| Component/Area | Possible Cause | Diagnostic Steps |
|---|---|---|
| Microphone | Defective Microphone | Inspect microphone for physical damage. Test microphone output with a multimeter (if specifications are available). * Substitute with a known good microphone. |
| Wiring Harness | Open Circuit in Wiring | Visually inspect wiring harness for damage, corrosion, or loose connections. Use a multimeter to check for continuity between the microphone connector and the BCM connector. * Wiggle the wiring harness while monitoring the signal with a scan tool to identify intermittent opens. |
| Wiring Harness | Short to Ground/Voltage | Check the wiring harness for any signs of chafing or damage that could cause a short. Use a multimeter to check for continuity between the microphone signal wire and ground. * Use a multimeter to check for voltage on the microphone signal wire when it should be grounded. |
| Connectors | Corroded or Loose Connectors | Inspect connectors at the microphone and BCM for corrosion, bent pins, or loose connections. Clean connectors with electrical contact cleaner. * Ensure connectors are properly seated and locked. |
| Body Control Module (BCM) | Faulty BCM | Check for other DTCs related to the BCM. Inspect the BCM connector for damage or corrosion. Perform BCM diagnostic tests with a scan tool (if available). As a last resort, consider BCM replacement (requires programming). |
| Ground Circuit | Poor Ground Connection | Locate the ground connection for the microphone circuit. Inspect the ground connection for corrosion or looseness. Clean and tighten the ground connection. Check for voltage drop across the ground connection while the system is active. |
| Software/Firmware | Outdated Software | Check for available software updates for the BCM or infotainment system. Update the software according to the manufacturer's instructions. |
| Interference | Electromagnetic Interference (EMI) | Check for aftermarket electrical components that could be causing interference. Ensure microphone wiring is properly shielded. * Reroute microphone wiring away from potential sources of EMI. |
Detailed Explanations
Microphone: The microphone is the input device that converts sound waves into an electrical signal. A defective microphone may not produce a sufficient signal, leading to the B1899 code. This can be due to internal damage or a degraded diaphragm.
Wiring Harness: The wiring harness carries the electrical signal from the microphone to the BCM. An open circuit in the wiring harness prevents the signal from reaching the BCM, triggering the B1899 code. This can be caused by broken wires, corrosion, or damage from rodents or heat.
Wiring Harness (Short to Ground/Voltage): A short circuit occurs when the microphone signal wire comes into contact with ground or a voltage source. This can disrupt the signal and cause the B1899 code. This is typically caused by damaged insulation.
Connectors: Connectors provide the electrical connection between the microphone, wiring harness, and BCM. Corroded or loose connectors can impede the signal flow, resulting in the B1899 code. Cleaning and securing these connections is often a simple fix.
Body Control Module (BCM): The BCM is a computer that controls various functions in the vehicle, including the microphone input. A faulty BCM may not be able to properly process the microphone signal, leading to the B1899 code. This is often a last resort diagnosis, as BCM issues can be complex.
Ground Circuit: A good ground connection is essential for proper circuit operation. A poor ground connection can cause voltage drop and disrupt the microphone signal, triggering the B1899 code. Ensuring a clean and tight ground connection is crucial.
Software/Firmware: Outdated software in the BCM or infotainment system can sometimes cause communication issues with the microphone. Updating the software can resolve these issues and eliminate the B1899 code.
Interference: Electromagnetic Interference (EMI) from other electrical components can disrupt the microphone signal. Shielding the microphone wiring and rerouting it away from potential sources of EMI can help resolve this issue.
Frequently Asked Questions
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What does the B1899 code mean? It indicates an open circuit in the microphone input signal circuit, meaning the vehicle's computer isn't receiving the expected signal from the microphone.
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Can I fix the B1899 code myself? Potentially, if you have basic automotive diagnostic skills and tools like a multimeter. Start with simple checks like inspecting the microphone and connectors. If you're not comfortable, consult a qualified mechanic.
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Will the B1899 code affect my vehicle's performance? It won't affect the engine or driving performance, but it will disable features that rely on the microphone, such as hands-free calling or voice commands.
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How much will it cost to fix the B1899 code? The cost varies depending on the cause. A simple fix like cleaning connectors might be inexpensive, while replacing the BCM could be costly. A diagnostic fee is typically involved before the repair.
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What tools do I need to diagnose the B1899 code? A multimeter is essential for checking continuity and voltage. A scan tool can be helpful for reading DTCs and monitoring signals. Other tools may include electrical contact cleaner, wire strippers, and crimpers.
Conclusion
The B1899 microphone input signal circuit open code indicates a break in the communication pathway between the microphone and the vehicle's computer. By systematically checking the microphone, wiring, connectors, and BCM, you can identify and resolve the issue, restoring functionality to microphone-dependent features. Remember to consult a qualified mechanic if you're unsure about any diagnostic or repair procedures.