Code
C951
CITROEN
C — Chassis
Fault on the left-hand rear audio output: Open circuit
Views:
UK: 3
EN: 3
RU: 2
AI status
Completed
Completed
100%
Causes
- Broken or chafed speaker wiring (open circuit)
- Disconnected or pushed-out speaker connector
- Failed left rear speaker (open voice coil)
- Corroded/poor connector or pin contact
- Faulty amplifier/head unit output stage (open)
- Blown audio fuse or interrupted power/ground to amplifier
Symptoms
- No sound from left rear speaker
- Audio imbalance (missing rear-left channel)
- Left rear channel warnings or audio system error message
- Intermittent sound when moving wiring/trim
- Low or distorted output from affected speaker area
What to check
- Scan audio/head unit and amplifier for stored codes; record freeze data before clearing
- Visually inspect left rear speaker, connector and wiring for damage, corrosion or loose pins
- Check related fuses and amplifier power/ground connections
- Measure speaker DC resistance at speaker connector with wiring disconnected
- Backprobe amplifier/head unit output connector while playing a test tone (low volume) — observe AC output
- Perform wiggle test on wiring between amplifier and speaker while audio is active to reproduce fault
Signal parameters
- Expected speaker DC resistance (typical): ~2–8 ohms (manufacturer dependent)
- Continuity at speaker connector: present (infinite = open)
- Amplifier supply voltage: 11–14 V (battery voltage) at power pins
- Amplifier output DC offset (idle):
- Audio output AC when playing test tone: measurable AC voltage (tens to hundreds of mV to volts depending on volume)
- No short to battery or ground on output (no low-resistance short)
Diagnostic algorithm
- Confirm symptom with vehicle on and audio at low volume; duplicate complaint
- Use scan tool to read/record C951 and any related codes; note freeze frame and noise/test tone options
- Inspect fuse(s) for audio/amplifier; verify amplifier power and ground connections are solid
- Remove left rear speaker and measure DC resistance across its terminals; an open (OL) indicates speaker failure
- With speaker disconnected, measure continuity between speaker connector and amplifier/head unit output pin; open = wiring or connector fault
- If continuity to amplifier is OK, connect a known-good speaker or swap with another channel; if sound returns, replace original speaker
- If the fault follows the amplifier output (no sound on that output even with known-good speaker), test amplifier output voltage and waveforms with a low-level audio tone; if output is absent, suspect amplifier/head unit
- Perform wiggle tests and inspect harness in areas prone to damage (hinge, trunk entry) to find intermittent opens
- Repair or replace damaged wiring or connectors; replace speaker if open voice coil; replace amplifier/head unit only after confirming upstream wiring and speaker are good
- Clear codes and road-test; re-scan to confirm C951 no longer present
Likely causes
- Open/disconnected speaker harness or terminal
- Speaker voice coil open (speaker failure)
- Damaged connector or corrosion at speaker or amplifier
- Wire break at body hinge or in trunk area
- Amplifier output transistor or internal circuitry failed
Fault status
Status
Left rear audio output: open circuit detected (no continuity/signal to speaker).
Repair difficulty: Medium
Diagnostic time: 0.5 - 1.5 hours
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