Troubleshooting Oxygen Sensor CircuitsIf system and component testing does not directly indicate any defects, it may be necessary to check the system wiring and the power supply relay using the information below along with the appropriate circuit diagrams found in CURRENT FLOW DIAGRAMS. If there is no voltage reaching the frequency valve connector as described in Checking Frequency Valve, remove the fuel injection power supply (or lambda) relay from its position on the fuse/relay panel. Check for voltage from the battery to the relay when the fuel pump operates. Check for continuity between the relay and the frequency valve. If both conditions are met, the relay should be replaced. The control unit also receives voltage via the fuel injection power (or lambda) relay. With the harness connector to the control unit disconnected, there should be voltage reaching the connector from the relay whenever the fuel pump is running. In addition, there must be continuity in the wires from the frequency valve, the thermoswitch, the control unit ground, and the green oxygen sensor wire to the control unit connector. If not, repair any faulty wiring and then redo the test. |
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