What Does B1899 Mean?
B1899 indicates the Body Control Module (BCM) has detected an open circuit in the microphone input signal path. This code is typically associated with hands-free telephone systems, voice recognition, or emergency call systems where a microphone is used for communication. The BCM has determined that the electrical continuity between the microphone and the control module has been interrupted or is not present.
Common Causes
40%
Broken or disconnected wiring between microphone and BCM, including corroded or loose connector pins
35%
Failed or internally open microphone assembly
15%
Damaged wiring from headliner removal, sunroof service, or accessory installation
10%
Failed Body Control Module with internal microphone circuit damage
Diagnostic Steps
1
Step 1: Perform visual inspection of the microphone assembly (typically located in overhead console, rearview mirror base, or A-pillar) for physical damage, water intrusion, or disconnected connectors. Check connector lock mechanisms and pin condition.
2
Step 2: Using a digital multimeter, measure resistance across the microphone terminals at the microphone connector. A functional dynamic microphone should show 200-600 ohms, electret microphones should show higher resistance with bias voltage present. Infinite resistance confirms internal microphone failure.
3
Step 3: Backprobe the microphone signal wire at the BCM connector with multimeter set to continuity mode while accessing the microphone end. Confirm continuity through the entire harness. Check for shorts to ground or power on the signal wire (should show infinite resistance to ground and power).
4
Step 4: If wiring and microphone test good, verify BCM is providing proper bias voltage (typically 2-5 volts DC) on the microphone power supply wire. No voltage present may indicate BCM internal circuit failure.
5
Step 5: Repair or replace identified faulty component (wiring, connector, or microphone). Clear codes and verify proper microphone operation through vehicle's hands-free or voice recognition system test function.
6
Step 6: If all external components test within specifications, consider BCM replacement or reprogramming as last resort after verifying all Technical Service Bulletins for the specific vehicle.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
B1899 indicates the Body Control Module (BCM) has detected an open circuit in the microphone input signal path. This code is typically associated with hands-free telephone systems, voice recognition, or emergency call systems where a microphone is used for communication. The BCM has determined that ...
The most common cause of B1899 (Microphone Input Signal Circuit Open) is: Broken or disconnected wiring between microphone and BCM, including corroded or loose connector pins
Typical repair costs for B1899 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle drivability or safety systems. The vehicle is safe to continue driving, though hands-free calling, voice commands, and emergency call features will be inoperative until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1899 to identify the root cause.
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Quick Info
Category
Body
System
Hands-Free Communication/Infotainment System
Difficulty
Type
Manufacturer
Recommended Tools
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