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Home >> Toyota >> 1989 >> Corolla LE, Standard, C50 >> Repair and Diagnosis >> Engine Performance >> System >> Tests W/Codes >> Code 21 - O2 Sensor Signal (4A-F) >> Probable Causes

July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

Probable Causes

Oxygen Sensor or Sensor Circuit
ECU

NOTE: Diagnostic chart not available from manufacturer.

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