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Home >> Jaguar >> 2000 >> XJ8 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Trouble Code Identification >> DTC P0031: Ho2S Heater Control Circuit Low Current (Bank 1, Upstream 1) >> Diagnostic Test Procedure

Diagnostic Test Procedure

  1. Turn ignition off. Disconnect HO2S harness connector. Turn ignition on. Make sure the O2S heater relay is energized and measure the voltage between HO2S harness connector terminal No. 2 and ground. Is voltage greater than 10 volts? If yes, go to next step. If no, repair the power supply circuit to the HO2S heater. This circuit includes the O2S heater relay, the EMS control relay and the EMS fuse box (fuse No. 14).
  2. Disconnect negative battery cable. Disconnect the ECM connector EM85. Measure resistance between ECM harness connector EM85 terminal No. 1 and HO2S harness connector terminal No. 1. Is resistance greater than 5 ohms? If yes, repair wiring as necessary. If no, go to next step.
  3. Reconnect negative battery cable. Turn ignition on. Measure voltage between HO2S harness connector terminal No. 1 and ground. Is voltage greater than 10 volts? If yes, repair short to voltage. If no, go to next step.
  4. Turn ignition off. Measure resistance between HO2S harness connector terminal No. 1 and ground. Is resistance less than 10,000 ohms? If yes, repair short to ground. If no, replace HO2S. See HEATED OXYGEN SENSOR (HO2S) under ENGINE SENORS in REMOVAL, OVERHAUL & INSTALLATION article. If DTC resets, possible ECM failure.
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