Body, generic

B0450 Microphone Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The code B0450 is absent from the publicly accessible J2012 lists, and no carmaker publishes it, so it remains unverified. Its title covers the hands-free microphone line. The module puts a bias voltage on the signal wire and reads speech back on the same wire. On the 2011 Saab 9-5 and its 9-4X sibling the OnStar module logs B2455 once the signal wire has been broken, grounded or tied to supply, or the low-reference return has lost contact, for 10 s; the status LED turns red and the other party cannot hear the caller. Audio converters like TI's PCM6240-Q1 supply a 5–9 V bias and flag open or shorted inputs and shorts to ground, bias or battery. Calls and voice control still start, but the far end hears nothing. Pairing problems belong to B0440.

Likely causes

Microphone in the headliner or mirror failed
Microphone wire pinched or broken in the headliner or A-pillar
Plug at microphone or module loose or corroded

Symptoms

  • Caller cannot hear the driver during hands-free calls
  • Voice control does not react to spoken commands
  • Emergency call or telematics status lamp shows a fault

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–300
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

microphoneinfotainment moduletelematics module

Related codes

B0440U0198

References: saabwisonline.com, saabwisonline.com, ti.com, ti.com.