Code
C91A
CITROEN
C — Chassis
Fault on the right-hand rear audio output: Open circuit
Views:
UK: 7
EN: 8
RU: 5
AI status
Completed
Completed
100%
Causes
- Broken or disconnected speaker lead (open circuit)
- Faulty right‑rear speaker (voice coil open)
- Corroded/damaged connector at speaker or amplifier
- Broken wiring or damaged harness in trunk/door area
- Faulty head unit / external amplifier output stage or internal connector
- Poor ground or supply to amplifier causing false open detection
Symptoms
- No sound from right‑rear speaker
- Audio balance shifted toward left or front, or missing channel
- Intermittent audio from that speaker (when moving harness)
- Audio system reports speaker fault or displays an error
- Possible buzzing/distorted sound if partial connection
What to check
- Confirm customer symptom and audio balance/fader settings (ensure not muted or balanced off)
- Read and record fault memory from infotainment/amplifier module and note freeze‑frame data
- Visually inspect speaker and amplifier connectors for corrosion, water, or pin damage
- Inspect wiring along routing path (door hinge, trunk seal) for chafing or breaks
- Check for loose ground or power at amplifier/head unit
- Listen for speaker response while commanding audio (low volume test)
Signal parameters
- Expected speaker impedance: commonly 4–8 Ω (verify vehicle spec)
- Continuity: speaker coil should show a few ohms (typically 2–16 Ω depending on speaker)
- Open‑circuit: multimeter shows very high/OL resistance between speaker + and –
- Quiescent DC offset at amplifier outputs: typically mid‑rail voltage (varies by design); open detection sees no load current
- No audio signal measured at amplifier output indicates open between amp and speaker
Diagnostic algorithm
- Read/record DTCs from infotainment/amplifier; clear codes and reproduce symptom to confirm persistence.
- Verify audio settings (balance/fader/mute) and try another audio source to rule out software/source issues.
- With ignition on and audio playing low test tone, inspect/operate speaker connector at the speaker; gently back‑probe the speaker connector at the speaker while listening for signal. If no signal present, proceed.
- Remove speaker and measure DC resistance across speaker terminals with multimeter. If resistance is very high/OL, speaker is open — replace speaker and recheck.
- If speaker measures OK, back‑probe amplifier/output connector at the module with speaker connected. Check for continuity between amplifier pin and speaker connector pin; if open, trace and repair wiring/harness or replace damaged connector.
- If wiring continuity is good but amplifier output shows no signal or abnormal voltage, suspect amplifier/head unit output stage fault — verify power and ground to module, then consider module repair or replacement.
- After repairs, erase DTCs, test audio at different levels and sources, and perform a road check to confirm permanent fix.
Likely causes
- Disconnected or pushed‑out speaker connector at rear door/trunk
- Wire chafed or broken where it flexes (door hinge, trunk lid)
- Speaker failed (open voice coil)
- Connector pins corroded from water ingress
- Output stage of amplifier has failed
Fault status
Status
C91A — Right rear audio output: open circuit (no speaker load detected)
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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