DTC Confirmation Test (Overall Function Check)

WARNING: This page is about a different car, the 2002 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the following test to check overall function of rear HO2S circuit. During this test, DTC may not be confirmed.

DTC P0137 will set if rear HO2S minimum voltage is too high. DTC P0138 will set if rear HO2S maximum voltage is too low. DTC P0139 will set if rear HO2S response time is too long. DTC P0140 will set if rear HO2S voltage is too high. Possible causes are:

HO2S circuit open or shorted.
Defective HO2S.
Fuel pressure incorrect.
Defective injectors.

To check rear HO2S circuit, drive vehicle at a speed of more than 43 MPH for 2 consecutive minutes. Stop vehicle and leave engine running. Measure voltage between ground and ECM terminal No. 56 (Brown wire). See Figure and Figure . Monitor voltage while quickly increase engine speed to 4000 RPM and release accelerator pedal. Repeat 10 times.

Voltage should be less than .48 volt at least once (DTC P0137).
Voltage should be more than .57 volt at least once (DTC P0138).
Voltage should change at least .06 volt in one second (DTC P0139).
Voltage should be less than 1.4 volts during test (DTC P0140).

If voltage is not as specified, allow engine to idle for 10 minutes and recheck voltage. If voltage is still not as specified, allow vehicle to coast at 50 MPH with overdrive off, then recheck voltage. If voltage is not as specified, perform DIAGNOSTIC PROCEDURE .