Code
B2455
HUMMER
B — Body
Open or short in Cellular Phone Microphone Circuit
Views:
UK: 16
EN: 23
RU: 17
AI status
Completed
Completed
100%
Causes
- Disconnected or loose microphone connector
- Broken or chafed wiring in microphone harness
- Short to ground or battery on the microphone signal or bias line
- Failed microphone element or microphone module
- Corrosion or water intrusion at connector or microphone assembly
- Faulty phone/Bluetooth module or infotainment control unit
Symptoms
- Hands‑free callers cannot hear vehicle occupant
- Very low or distorted outgoing voice quality during calls
- Bluetooth phone microphone shows as disabled or not present on infotainment
- Microphone warning or communication fault message on dash/information display
- DTC B2455 (open/short) stored in body or infotainment module
What to check
- Read and record stored DTCs and freeze frame data with a capable scan tool
- Visually inspect microphone assembly and connector for damage, corrosion or water intrusion
- Verify connectors at overhead console, headliner, and infotainment module are fully seated
- Inspect wiring route for chafes, pinches or previous repair splice points
- Perform wiggle test while monitoring microphone input on scan tool or during a call to reproduce fault
- Check for related radio/phone module faults or power/ground DTCs
Signal parameters
- Microphone bias (when system powered): approximately 2–3 V DC on the microphone power/bias line relative to chassis ground (varies by system)
- Microphone signal: varying audio voltage present when speaking (AC component over bias)
- Open circuit: infinite resistance between microphone pin and module pin; Short to ground: near 0 Ω between signal/bias and ground
- Expected continuity from microphone housing/connector pin to the module microphone input with reasonable resistance (low ohms through wiring)
Diagnostic algorithm
- Verify and record the DTC(s) with a scan tool; clear codes and attempt to reproduce fault.
- Visually inspect the in-cabin microphone(s) and connector(s) for damage, moisture or corrosion; reseat connectors.
- With ignition/accessory on, measure bias voltage at the microphone connector pin(s) relative to chassis ground. If no bias present, trace back to infotainment/phone module for power/bias supply issue.
- Check continuity between the microphone connector and the phone/infotainment module microphone input pin. Repair any open circuits.
- If a short to ground or battery is indicated, isolate sections of the harness and use backprobing to locate the short; repair damaged wiring/insulation.
- Substitute with a known good microphone (or known good wiring harness) if available to confirm microphone element failure.
- If wiring and microphone check OK, inspect module grounds and power feeds. Test or reflash the phone/infotainment module per service information, and consider module replacement only after wiring and microphone verified good.
- After repairs, clear DTCs and verify proper operation during a phone call and with the scan tool monitoring microphone input; road/test as required.
Likely causes
- Loose or unplugged in‑cab microphone connector
- Wiring damage in headliner, A‑pillar or dash harness (pinched during service)
- Microphone element failure due to moisture or impact
- Short to ground on the microphone bias/signal wire caused by frayed insulation
- Intermittent connector contact from corrosion
Fault status
Status
Detected open or short in cellular phone microphone circuit. Microphone signal or bias fault preventing proper hands‑free microphone operation.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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