left side engine. you cat converter is just about worn out.
P0420
DTC P0420 TWC System Low Efficiency Bank 1 (1 Of 2)
DTC P0420 TWC System Low Efficiency Bank 1 (2 Of 2)
TWC System
CIRCUIT DESCRIPTION
In order to control emissions of Hydrocarbons (**), Carbon Monoxide (CO) and Oxides of Nitrogen
(NOx), The 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, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The Vehicle Control Module
(VCM) has the capability to monitor this process using the HO2S (Bank 1, Sensor 1). The HO2S (Bank 1, Sensor 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 in turn indicates the catalyst's ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the HO2S (Bank 1, Sensor 2) signal will be far less active than that produced by the HO2S (Bank 1, Sensor 1). If a problem exists which causes the VCM to detect an excessive HO2S (Bank 1, Sensor 2) activity outside of an acceptable range for an extended period of time, the VCM sets the DTC P0420. This DTC indicates that the three-way catalytic converter's oxygen storage capacity is below a threshold considered acceptable. This is a type A DTC.
CONDITIONS FOR SETTING THE DTC
Converter Warm Up Test
- A Closed Loop.
- The commanded Air to Fuel ratio = 14.7:1.
- The Mass Air Flow (MAF) is greater than 15 g/s.
- The predicted Catalyst warm up temperature is greater than 450°C.
Converter Warm UP Test Passed
- No Vehicle Speed (VS) sensor DTCs.
- No Throttle Position (TP) sensor DTCs.
- No HO2S DTCs.
- No misfire DTCs.
- No Manifold Absolute Pressure (MAP) sensor DTCs.
- No fuel trim DTCs.
- No Intake Air Temperature (IAT) sensor DTCs.
- No Engine Coolant Temperature (ECT) sensor DTCs.
- No MAF sensor DTCs.
- Engine coolant temperature is above 75°C (167°F).
- The vehicle is in a Closed Loop fuel control.
- The above conditions met for a period of time in order to ensure a warm catalyst (at least 2 consecutive minutes).
- The calculated engine load is steady.
- Vehicle speed is steady between 20 mph and 70 mph.
- The IAT is at least -9.75°C.
- The MAF sensor is less than 50 g/s.
- The engine speed is no more than 4700 RPM.
- The TP sensor is more than 1.9%.
- Bank 1, Sensor 2 HO2S average is ±39 mV from Bank 1, Sensor 1 average voltage.
ACTION TAKEN WHEN THE DTC SETS
The
VCM will turn ON the
Malfunction Indicator Lamp (MIL).
CONDITIONS FOR CLEARING THE MIL/DTC
The
VCM turns the MIL off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.
DIAGNOSTIC AIDS
Difficulty running the OBD II status DTC P0420 test may be encountered in areas where the test conditions cannot be maintained easily, especially in urban areas.
TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.
- This table includes checks for conditions that can cause the three-way catalytic converter efficiency to appear degraded. Inspect and repair exhaust system as necessary. Inspect the HO2S (Bank 1, Sensor 2) pigtail and engine harness for any damage that can cause an intermittent fault in HO2S (Bank 1, Sensor 2) circuits.
CAUTION : In order to avoid damaging the replacement three-way catalytic converter, correct the engine misfire or mechanical fault before replacing the three-way catalytic converter.
- If the three-way catalytic converter needs to be replaced, make sure that the following conditions are not present to caused the catalyst to be damaged:
- Misfire.
- High engine oil consumption or coolant consumption.
- Retarded spark timing or weak spark.
