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Code 37 - Oxygen (O2) Sensor No. 2 - L/H

NOTE: Refer to illustration for ECM connector terminal identification. See Figure .
  1. Warm engine to operating temperature and allow to idle. Using a DVOM, check voltage between ECM connector terminal A5 (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 ECM connector terminals for good contact. Repair as necessary. If connector terminals are okay, replace ECM.
  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 off. Disconnect ECM connectors. Using an ohmmeter, check resistance between ECM connector terminal A5 and sensor connector terminal No. 4 (Yellow/Blue wire). Resistance should be zero ohms. Check resistance between sensor connector terminal No. 4 (Yellow/Blue 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. 1 (Black/White wire) and sensor connector terminal No. 1 (Black/White wire), and between main relay connector terminal No. 3 (White/Red 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 on. Using a DVOM, check voltage between ground and main relay connector terminals No. 2 (Brown/Black wire) and No. 1 (Black/White 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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