Hi billy1212,
Usually that means a bad catalytic coverter.
DTC P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD
NOTE: If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot those DTCs first, then recheck for DTC P0420.
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) Heater
1. Reset the ECM/PCM (see HOW TO RESET THE ECM/PCM ).
2. Start the engine. Hold the engine at 3,000 RPM with no load (in Park or neutral) until the radiator fan comes on.
3. Except F23A4 SULEV engine: Test-drive at 40-55 mph (64-88 km/h) for approx. 2 minutes. Then decelerate for at least 3 seconds with the throttle completely closed. Then reduce the vehicle speed to 35 mph (56 km/h), and try to hold it until the scan tool indicates FAIL or PASS as the TWC test result.
F23A4 SULEV engine: Test-drive at 50-55 mph (80-88 km/h) for approx. 2 minutes. Then decelerate for at least 4 seconds with the throttle completely closed. Then accelerate to 55 mph (88 km/h), and try to hold it until the scan tool indicates FAIL or PASS as the TWC test result.
Is the test result FAIL?
YES -Check the three way catalytic converter (TWC). If necessary, replace the TWC.
NO -Intermittent failure, system is OK at this time.
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Friday, February 20th, 2009 AT 3:12 PM
