P0430
CIRCUIT DESCRIPTION
In order to maintain a reasonably low emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), the engine controls system uses a three-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and Carbon Dioxide. The catalyst also reduces NOx, converting it to Nitrogen. The PCM monitors this process using Bank 1 HO2S #2. Bank 1 HO2S #2, located in the exhaust stream past the three-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signal will be far less active than that produced by Bank 1 HO2S #1. If a problem exists which causes the PCM to detect excessive Bank 1 HO2S #2 activity outside of an acceptable range for an extended period of time, the PCM will set DTC P0420. This indicates that the three-way catalytic converters oxygen storage capacity is below a threshold considered acceptable.
CONDITIONS FOR SETTING THE DTC
^ No AIR, CKP, CMP, IAT, IC, MAF, MAP, ECT, TP, EVAP, Left Bank HO2S, Misfire, Left Bank Fuel Trim, Injector, VSS, Engine Protection, or Transmission DTCs are set.
^ Engine is operating.
^ ECT is greater than 65°C (149°F).
^ Vehicle speed is less than 136 km/h (85 mph).
^ Throttle angle is greater than 10%.
^ Engine speed is less than 4000 RPM.
^ MAP is between 25 kPa and 80 kPa.
^ Air flow is between 14 gm/s and 40 gm/s.
^ Closed loop fuel control enabled.
^ The PCM determines oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.
ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
^ The PCM battery voltage is interrupted.
^ Use a scan tool in order to clear the MIL/DTC.
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
4. Before replacing the three way catalytic converter, make sure that any conditions which may have caused the catalyst to be damaged have been corrected.