DTC Confirmation Test (Using Generic Scan Tool)

WARNING: This page is about a different car, the 2003 Infiniti Q45. 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 3-way catalyst. During this test, 1st trip DTC may not be confirmed.

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

Start engine and warm to the normal operating temperature. Turn ignition off and wait at least 10 seconds. Start engine and keep the engine speed between 3500-4000 RPM for one minute under no load. Let engine idle for one minute. Measure voltage between engine ground and left front HO2S signal circuit at ECM terminal No. 114 (Red/Blue wire), or right front HO2S signal circuit at ECM terminal No. 115 (Blue/White wire), by backprobing. Also, measure voltage between ground and left rear HO2S signal circuit at ECM terminal No. 123 (Purple wire), or right rear HO2S signal circuit at ECM terminal No. 124 (Black wire), by backprobing. See Figure and Figure .
Increase engine speed to 2000 RPM and keep constant under no load. If switching frequency of rear HO2S is less than 75 percent of front HO2S switching frequency, catalyst is operating correctly. If switching frequency of rear HO2S is not less than 75 percent of front HO2S switching frequency, go to DIAGNOSTIC PROCEDURE . If front HO2S does not switch more than 5 times within 10 seconds, diagnose and repair front HO2S. See DTC P0133 OR P0153: BANK 1 OR BANK 2 HO2S1 (RESPONSE MONITORING) .