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Home >> Volvo >> 1995 >> 850 Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Turbo >> Diagnostic Trouble Code Testing >> MOTRONIC 4.3 Control System >> Code 4-2-5: Rear HO2S Lambdasond
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Code 4-2-5: Rear HO2S Lambdasond

  1. Perform a compression check on all cylinders. Repair as necessary. If compression is okay, go to next step.
  2. Check for air leakage in intake system. Repair as necessary. If there is no air leakage in intake system, check for air leakage in exhaust system. Repair as necessary. If there is no air leakage in exhaust system, check fuel and residual pressure. Repair as necessary. If fuel and residual pressure are okay, retest using new HO2S.
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