Code
CF00
PEUGEOT
C — Chassis
Microphone input fault: Open circuit
AI status
Completed
Completed
100%
Causes
- Disconnected or loose microphone connector
- Broken or shorted wiring between microphone and audio/hands‑free module
- Failed microphone element (open internal wiring)
- Corroded or damaged connector pins
- Blown fuse or lost supply/bias voltage to microphone circuit
- Faulty hands‑free/audio module input or internal amplifier
Symptoms
- No voice picked up by hands‑free/voice recognition systems
- Callers report no sound from driver’s side microphone
- Hands‑free or voice control functions do not respond or show errors
- Related warning/message on infotainment display
- Stored DTC CF00 (microphone input open circuit) in audio/hands‑free module
What to check
- Read and record all stored DTCs and freeze frame data from the hands‑free/infotainment module
- Visually inspect microphone, grille, surrounding trim and connectors for damage or water ingress
- Check connector locked condition and presence of corrosion or bent pins
- Verify related fuses and power/battery supply for the audio/hands‑free module
- Inspect wiring harness route for chafing, pinches or recent interior repairs
- Use a diagnostic tool to monitor microphone input status and run built‑in microphone tests if available
Signal parameters
- Microphone bias voltage (typical): ~2–6 V DC on microphone supply pin with ignition/infotainment on
- DC continuity: open circuit expected if fault present; normal continuity: low kΩ range between microphone pins
- AC signal level when speaking: tens to hundreds of mV RMS (depends on microphone type and distance)
- Connector pin resistance to ground where applicable: should match wiring diagram specifications
- No signal present (0 V AC) at microphone input when speaking indicates open or disconnected circuit
Diagnostic algorithm
- Record CF00 and any other codes. Note occurrence conditions and last events.
- Confirm vehicle specifics and obtain the wiring diagram for the microphone circuit and connector pinout.
- Visually inspect the microphone area (roof lining/visor/dash), connector and wiring for damage, corrosion or water ingress. Reseal or replace damaged trim if found.
- With ignition on (follow manufacturer safety steps), check for microphone bias voltage at the microphone connector supply pin using a multimeter. If bias missing, trace back to fuse/module power.
- Check continuity between the microphone plug and the module input pin. An open indicates a broken wire or disconnected connector; repair wiring as needed.
- While a helper speaks, measure AC signal at the microphone input at the module end. No AC signal with proper bias suggests internal microphone open or connector issue.
- Wiggle test harness and connectors while monitoring signal/voltage and DTCs to find intermittent faults.
- If possible, swap in a known good microphone or substitute with a test microphone per workshop procedures to confirm microphone vs module fault.
- If microphone and wiring test good, consider module input failure—verify communications and power rails, then follow manufacturer procedure for module replacement or repair.
- Repair or replace the faulty component(s), clear codes, and retest system operation and voice/hands‑free functions. Confirm no reappearance of CF00.
Likely causes
- Connector unplugged or poor contact at microphone
- Broken wire (wear, chafing, or pinched harness) between microphone and module
- Microphone element open (component failure)
- Corroded connector or water ingress at microphone assembly
- Module input failure (rare)
Fault status
Status
Microphone input open circuit detected by the hands‑free/audio module — microphone signal absent or wiring open.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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