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 front HO2S circuit. During this test, first trip DTC may not be confirmed.

Malfunction is detected when front HO2S "rich" output is not high enough or "lean" output is not low enough. DTC will set if both "rich" and "lean" outputs are shifted to the rich side. Possible causes are:

Defective HO2S.
Defective HO2S heater.
Fuel pressure incorrect.
Defective injectors.

CAUTION: DO NOT use ECM ground terminals when measuring voltage.

To check front HO2S circuit, start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 50 (Light Green wire) by backprobing. See Figure and Figure . Monitor voltage while holding engine speed at 2000 RPM. The following conditions should exist:

Maximum voltage should be less than .8 volt at least once.
Minimum voltage should be less than .35 volt at least once.

If voltage is not as specified, perform DIAGNOSTIC PROCEDURE .