FixVault
Home › Land Rover › 1994 › Discovery Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls - System & Component Testing › Sensors & Switches › Heated Oxygen Sensor Circuit

Heated Oxygen Sensor Circuit

  1. Start and run engine until it reaches normal operating temperature. Access Engine Control Module (ECM), located behind right fascia. See Figure . Backprobing, measure voltage between ECM connector terminals No. 23 (Blue wire) and 4 (Black wire) for left Heated Oxygen Sensor (HO2S), or terminals No. 24 (Blue wire) and 4 (Black wire) for right HO2S. See Figure . Voltage should be fluctuating between 0.5-1.0 volts. If voltage is as specified, HO2S is okay. If voltage is not as specified, go to next step.
  2. If voltage is steady around 0.5 volts, check for vacuum leaks, faulty of contaminated injectors or low fuel pressure. If voltage is steady around 1.0 volts, check for high fuel pressure, leaking injectors or saturated carbon canister. Repair as necessary. If no problem is found, check for short or open in Blue wire between ECM and HO2S or Black wire between HO2S and ground. If wires are okay, replace HO2S.
About FixVault