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Code 37 - Oxygen (O2) Sensor No. 2

NOTE: Refer to illustration for ECU connector and terminal identification. See Figure .
  1. Warm engine to operating temperature and allow to idle. Using a DVOM, check voltage between ECU connector B61, terminal No. 5 (backprobe) and ground. Voltage should vary between 0.1 volt and 1.0 volt. If voltage is not as specified, go to next step. If voltage is as specified, check ECU connector terminals for good contact. Repair as necessary. If connector terminals are okay, replace ECU.
  2. With engine at idle, disconnect oxygen sensor connector, located on left side of engine. Using a DVOM, check voltage between sensor connector terminal No. 4 (Yellow/Blue wire) and ground. Voltage should vary between 0.1 volt and 1.0 volt. If voltage is as specified, go to next step. If voltage is not as specified, replace left oxygen sensor.
  3. Turn ignition switch to OFF position. Disconnect ECU connectors. Using an ohmmeter, check resistance between ECU connector B59, terminal No. 5 and sensor connector terminal No. 4 (Yellow wire). Resistance should be zero ohms. Check resistance between sensor connector terminal No. 4 (Yellow wire) and ground. Resistance should be one megohm or greater. If resistances are as specified, go to next step. If resistances are not as specified, repair circuit as necessary.
  4. Disconnect main relay connector. Using an ohmmeter, check resistance between main relay connector terminal No. 2 (Brown/Black wire) and sensor connector terminal No. 1 (Black/White wire), and between main relay connector terminal No. 4 (Yellow wire) and sensor connector terminal No. 2 (White/Red wire). Resistance should be zero ohms for both circuits. If resistance is as specified, go to next step. If resistance is not as specified, repair appropriate circuit as necessary.
  5. Turn ignition switch to ON position. Using a DVOM, check voltage between ground and main relay connector terminals No. 2 (Brown/Black wire) and No. 4 (Yellow wire). Voltage should be 10 volts or greater. If voltage is as specified, replace main relay. If voltage is not as specified, repair appropriate circuit as necessary.
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