DTC P0420: Catalyst 1/1 Efficiency Failure
NOTE:
Catalyst efficiency is monitored after engine is at 170°F (77°C), throttle has been open for 180 seconds, vehicle speed is greater than 20 MPH with engine at 1200-1600 RPM and MAP sensor vacuum is 15-18 in. Hg. DTC may be stored in Powertrain Control Module (PCM) if catalyst efficiency deteriorates and switching rate of downstream oxygen sensor become nearly the same as upstream oxygen sensor. If at any point during the test, if switch rate reaches a predetermined value, a counter is incremented by one. Possible causes are: engine mechanical problem, exhaust leak, defective catalytic converter or upstream oxygen sensor is older than the downstream oxygen sensor.
- Turn ignition on with engine off. Using scan tool, check for DTCs. If global good trip counter is not displayed and equal to zero, go to next step. If global good trip counter is displayed and equal to zero, go to step 3.
- At this time, conditions for catalyst efficiency failure does not exist or is an intermittent problem. Using scan tool, read FREEZE FRAME data while attempting to duplicate the condition that caused DTC to be set by paying special attention to the conditions that catalyst efficiency failure is monitored. Catalyst efficiency is monitored after engine is at 147°F (64°C), throttle has been open for 180 seconds, vehicle speed is greater than 20 MPH with engine at 1200-1600 RPM and MAP sensor vacuum is 15-18 in. Hg. If DTC reoccurs, go to next step. If DTC does not reoccur, condition no longer exists. Perform TEST VER-5A .
- Start engine and allow engine to idle. Check for exhaust leaks between engine and downstream oxygen sensor. Downstream oxygen sensor is located on exhaust pipe, behind catalytic converter. Downstream oxygen sensor may also be referred to as 1/2 O2 sensor. If no exhaust leaks exist, go to next step. If exhaust leaks exist, repair as necessary. Perform TEST VER-5A .
- Check exhaust for excessive smoke caused by coolant entering combustion chambers or high oil consumption. If excessive smoke caused by coolant entering combustion chambers or high oil consumption is not present, go to next step. If excessive smoke caused by coolant entering combustion chambers or high oil consumption is present, repair engine as necessary and replace catalytic converter. Perform TEST VER-2A .
- Determine if downstream oxygen sensor has been replaced without replacing the upstream oxygen sensor, as a newly installed downstream oxygen sensor with an existing aging upstream oxygen sensor may cause DTC to be set. If downstream oxygen sensor has been replaced without replacing upstream oxygen sensor, replace upstream oxygen sensor. Perform TEST VER-5A . If downstream oxygen sensor has not been replaced without replacing upstream oxygen sensor, replace catalytic converter. Perform TEST VER-5A .