Ok, here is the def I get with Mitchell1.
DTC P0420 OR P0430: THREE-WAY CATALYST FUNCTION
Use the following test to check overall function of three-way catalyst. During this test, first trip DTC may not be confirmed.
Malfunction is detected when switching frequency of rear HO2S increases to a specified value, indicating that three-way catalyst does not operate properly. Possible causes are:
Defective three-way catalyst.
Intake air leaks.
Defective spark plugs.
Incorrect ignition timing.
CAUTION:DO NOT use ECM ground terminals when measuring voltage.
To check overall function of three-way catalyst, 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 terminals No. 63 (right front HO2S), No. 62 (left front HO2S), No. 72 (right rear HO2S) and No. 71 (left rear HO2S) by backprobing. See Fig. 3 and Fig. 4. Increase engine speed to 2000 RPM. Switching frequency of rear HO2S should be less than 75 percent of front HO2S switching frequency. If operation is not as specified, go to PROCEDURE. If front HO2S does not switch more than 5 times within 10 seconds, diagnose and repair front HO2S. See DTC P0133: RIGHT BANK, OR DTC P0153: FRONT HEATED OXYGEN SENSOR.
1. Visually inspect exhaust system for damage or leaks. Start engine and run at idle. Check for exhaust leak in front of three-way catalyst. Check for intake air leak after MAF sensor. Repair or replace faulty components as necessary and retest system. If no problems exist, go to next step.
2. Check ignition timing, closed throttle position switch idle position adjustment and target idle speed. See ON-VEHICLE ADJUSTMENTS article. Adjust, if necessary and retest system. If no adjustments are necessary, go to next step. 3. Turn engine off and turn ignition on. Measure voltage between ground and ECM terminals No. 101, 102, 103, 104, 105 and 107 by backprobing. See Fig. 3 and Fig. 4. If battery voltage exists at each terminal, go to next step. If battery voltage does not exist at all terminals, repair appropriate injector or circuit and retest system. See SYSTEM & COMPONENT TESTING article. 4. Turn ignition off. Remove ignition coils from rocker covers. Connect a known-good spark plug to coil and ground spark plug end. Crank engine and check for spark. If spark exists at all coils, go to next step. If spark does not exist at all coils, diagnose fault in coil or coil circuit and retest system. See DTC P1320: IGNITION SIGNAL. 5. Turn ignition off. Remove injector assembly, keeping fuel hose and all injectors connected. Turn ignition on. Verify fuel is not dripping from any injectors. Replace any injectors from which fuel is dripping and retest system. If all injectors are okay, go to next step. 6. Problem may be intermittent. Attempt to recreate conditions present when DTC was set. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If no problems are found, replace three-way catalyst and retest system.
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Saturday, December 18th, 2010 AT 9:59 PM