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Home >> Infiniti >> 2003 >> QX4 4WD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Bank 1 Catalyst System Efficiency - Below Threshold Or P0430: Bank 2 Catalyst System Efficiency - Below Threshold >> DTC Confirmation Test (Using Generic Scan Tool)
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DTC Confirmation Test (Using Generic Scan Tool)

NOTE: Use the following test to check overall function of warm-up 3-way catalyst. During this test, 1st trip DTC may not be confirmed.
CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  1. Start engine and warm to normal operating temperature. Turn ignition off for at least 10 seconds. Start engine and run at 3500-4000 RPM for at least one minute under no load. Let engine idle for one minute. Backprobbing at ECM, measure voltage between ground and ECM terminal No. 63 (bank 1) or No. 62 (bank 2). See Figure and Figure . Also, measure voltage between ground and ECM terminal No. 72 (bank 1) or No. 71 (bank 2).
  2. Increase engine speed to 2000 RPM under no load. If switching frequency of HO2S 2 is less than 75 percent of HO2S 1 switching frequency, catalyst is operating properly. If switching frequency of HO2S 2 is not less than 75 percent of HO2S 1 switching frequency, go to DIAGNOSTIC PROCEDURE . If HO2S 1 does not switch more than 5 times within 10 seconds, diagnose and repair HO2S 1 before continuing with this procedure. See DTC P0133 OR DTC P0153 .
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