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U0178 Lost Communication With Restraints System Sensor I

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0178 covers restraint sensor I, the ninth remote crash sensor; unlike many letter series, J2012 does use the letter I here. No manufacturer documents U0178 publicly. High sensor counts come mainly from combining sensor types: Bosch connects two or four door pressure sensors to the airbag unit in addition to the acceleration sensors on the body structure, so a four-door car can easily exceed eight satellites. A pressure sensor in the door cavity registers the pressure rise when the door is pushed in. Its wiring passes through the door hinge area, where repeated opening can break conductors, and water inside the door can reach the connector. Such sensors are often linked via PSI5, a two-wire interface. U0479 reports invalid data from the same sensor. No MIL.

Likely causes

Broken wire in the door hinge passage
Water inside the door at the sensor connector (failed vapour barrier)
Sensor I failed
Sensor interface of the airbag unit faulty

Symptoms

  • Airbag warning lamp on
  • Fault may come and go with door movement
  • Impact detection in the zone of sensor I unavailable

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€60–600
Time0.5–3 h

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

Parts involved

restraints sensor icrash signal wiring

Related codes

U0151U0177U0179U0479

References: bosch-mobility.com, psi5.org, en.wikipedia.org.