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Home >> Porsche >> 1985 >> 928 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - BOSCH LH >> Testing >> Test 21 >> Oxygen Sensor & LH Control Unit
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Oxygen Sensor & LH Control Unit

  1. To check oxygen sensor, warm up engine to operating temperature. Check idle speed. Disconnect oxygen sensor plug. Connect voltmeter to ground and to the sensor wire (female plug). Reading should be .1-1.0 volts. If not, replace oxygen sensor.
  2. To check LH control unit, connect CO tester to one of the 2 test pipes in engine compartment. Warm up engine to operating temperature and check idle speed. Disconnect oxygen sensor plug. Recheck CO level. Connect oxygen sensor Green wire on plug to ground. If CO does not increase, check wire from LH control unit terminal 20 to oxygen sensor. If wire is okay, replace LH control unit.
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