B1D79

Code

LAND ROVER B — Body

Microphone input

Brand: LAND ROVER

Type: B — Body

Views: UK: 9 EN: 17 RU: 11

AI status

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Page language: EN

Causes

Faulty microphone element (electret or digital mic)
Open, shorted or corroded wiring between microphone and control unit
Poor or loose connector or pin corrosion at microphone or module
Incorrect microphone bias or supply (open fuse, damaged supply line)
Faulty infotainment/head unit, audio interface module or microphone preamp
Software/firmware error or calibration issue

Symptoms

Voice recognition or hands-free voice calls unavailable or poor quality
Microphone not detected in system diagnostics
Intermittent voice pickup or distorted/weak audio
Related fault indicator or stored DTCs for audio/microphone circuits

What to check

Check for any related stored DTCs in the infotainment or vehicle control modules
Visual inspection of microphone location, mounting and connectors for damage, water ingress or corrosion
Inspect wiring harness routing for pinched, chafed or damaged areas
Check fuses and power supply circuits that feed microphone bias
Use vehicle diagnostic tool to view live microphone input values (if available)
Listen for microphone operation during a hands-free call or voice command test

Signal parameters

Bias/supply: typical electret microphone bias commonly 2–5 V DC (varies by vehicle). Verify manufacturer spec for exact value.
Idle/DC level: analog mic line typically rests near a mid-rail bias voltage (manufacturer dependent).
AC signal: voice-level AC amplitude typically tens to a few hundred millivolts when speaking directly into mic.
Impedance: microphone element typically has kΩ-range impedance; check vehicle spec.
Digital mics: may use I2S/PCM or digital bus — verify presence of clock/data signals with an oscilloscope or scope-capable scan tool.

Diagnostic algorithm

Retrieve all related DTCs and freeze frame data with a scan tool; note module reporting B1D79 and any related codes.
Perform visual inspection: check microphone(s), mounting, grommets, connectors and harness for damage or contamination (water, adhesive, corrosion).
Check fuses and power feeds for the audio/infotainment module and microphone supply circuit.
With connector connected, backprobe or access microphone connector and measure DC bias voltage relative to ground. Compare to manufacturer specification (typical 2–5 V for electret mics).
If bias present, measure AC signal while someone speaks into the microphone (use oscilloscope or high-sensitivity AC meter). Confirm presence of voice waveform.
If no bias or signal present, inspect continuity between module and microphone connector; repair any open/shorted wires or damaged pins.
If bias and wiring are good but no valid signal, temporarily substitute a known-good microphone (if available) to confirm microphone versus module failure.
If substituted mic works, replace defective microphone and clear codes. If still fails, suspect head unit/audio interface module — perform module-level tests or replacement as per factory procedure.
Check for software updates or calibration procedures for infotainment/voice system and perform as required.
After repairs, clear DTCs, perform full system test of voice recognition and hands-free calling, and verify no reoccurrence of the code.

Likely causes

Microphone failure (most common)
Wiring harness damage near dash/roof/steering column
Connector corrosion or poor pin contact
Blown fuse or no bias voltage to microphone
Failed audio input stage in head unit or BCM

Fault status

⚠️ Status

Microphone input fault — signal missing, out of range, or short/open detected. Voice recognition/hands-free audio may be impaired.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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Repair manuals

Manual library for LAND ROVER

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Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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