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P0420 OBD-II Trouble Code
Technical Description
Catalyst System Efficiency Below Threshold (Bank 1)
What does that mean?
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms
You will likely not notice any drivability problems, although there may be symptoms.
Causes
A code P0420 may mean that one or more of the following has happened:
* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing
* The oxygen sensors in front and behind the converter are reporting too similar of readings
Possible Solutions
Some suggested steps for troubleshooting a P0420 code include:
* Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
* Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
* Inspect the downstream heated oxygen sensor (HO2), replace if necessary
* Replace the catalytic converter
# P0400 Exhaust Gas Recirculation Flow Malfunction
# P0401 Exhaust Gas Recirculation Flow Insufficient Detected
# P0402 Exhaust Gas Recirculation Flow Excessive Detected
# P0403 Exhaust Gas Recirculation Circuit Malfunction
# P0404 Exhaust Gas Recirculation Circuit Range/Performance
# P0405 Exhaust Gas Recirculation Sensor A Circuit Low
# P0406 Exhaust Gas Recirculation Sensor A Circuit High
# P0407 Exhaust Gas Recirculation Sensor B Circuit Low
# P0408 Exhaust Gas Recirculation Sensor B Circuit High
# P0410 Secondary Air Injection System Malfunction
# P0411 Secondary Air Injection System Incorrect Flow Detected
# P0412 Secondary Air Injection System Switching Valve A Circuit Malfunction
# P0413 Secondary Air Injection System Switching Valve A Circuit Open
# P0414 Secondary Air Injection System Switching Valve A Circuit Shorted
# P0415 Secondary Air Injection System Switching Valve B Circuit Malfunction
# P0416 Secondary Air Injection System Switching Valve B Circuit Open
# P0417 Secondary Air Injection System Switching Valve B Circuit Shorted
# P0418 Secondary Air Injection System Relay .A" Circuit Malfunction
# P0419 Secondary Air Injection System Relay "B. Circuit Malfunction
# P0420 Catalyst System Efficiency Below Threshold (Bank 1)
# P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)
# P0422 Main Catalyst Efficiency Below Threshold (Bank 1)
# P0423 Heated Catalyst Efficiency Below Threshold (Bank 1)
# P0424 Heated Catalyst Temperature Below Threshold (Bank 1)
# P0430 Catalyst System Efficiency Below Threshold (Bank 2)
# P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)
# P0432 Main Catalyst Efficiency Below Threshold (Bank 2)
# P0433 Heated Catalyst Efficiency Below Threshold (Bank 2)
# P0434 Heated Catalyst Temperature Below Threshold (Bank 2)
# P0440 Evaporative Emission Control System Malfunction
# P0441 Evaporative Emission Control System Incorrect Purge Flow
# P0442 Evaporative Emission Control System Leak Detected (small leak)
# P0443 Evaporative Emission Control System Purge Control Valve Circuit
# P0444 Evaporative Emission Control System Purge Control Valve Circuit
# P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted
# P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
# P0447 Evaporative Emission Control System Vent Control Circuit Open
# P0448 Evaporative Emission Control System Vent Control Circuit Shorted
# P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
# P0450 Evaporative Emission Control System Pressure Sensor Malfunction
# P0451 Evaporative Emission Control System Pressure Sensor Range/Performance
# P0452 Evaporative Emission Control System Pressure Sensor Low Input
# P0453 Evaporative Emission Control System Pressure Sensor High Input
# P0454 Evaporative Emission Control System Pressure Sensor Intermittent
# P0455 Evaporative Emission Control System Leak Detected (gross leak)
# P0460 Fuel Level Sensor Circuit Malfunction
# P0461 Fuel Level Sensor Circuit Range/Performance
# P0462 Fuel Level Sensor Circuit Low Input
# P0463 Fuel Level Sensor Circuit High Input
# P0464 Fuel Level Sensor Circuit Intermittent
# P0465 Purge Flow Sensor Circuit Malfunction
# P0466 Purge Flow Sensor Circuit Range/Performance
# P0467 Purge Flow Sensor Circuit Low Input
# P0468 Purge Flow Sensor Circuit High Input
# P0469 Purge Flow Sensor Circuit Intermittent
# P0470 Exhaust Pressure Sensor Malfunction
# P0471 Exhaust Pressure Sensor Range/Performance
# P0472 Exhaust Pressure Sensor Low
# P0473 Exhaust Pressure Sensor High
# P0474 Exhaust Pressure Sensor Intermittent
# P0475 Exhaust Pressure Control Valve Malfunction
# P0476 Exhaust Pressure Control Valve Range/Performance
# P0477 Exhaust Pressure Control Valve Low
# P0478 Exhaust Pressure Control Valve High
# P0479 Exhaust Pressure Control Valve Intermittent
# P0480 Cooling Fan I Control Circuit Malfunction
# P0481 Cooling Fan 2 Control Circuit Malfunction
# P0482 Cooling Fan 3 Control Circuit Malfunction
# P0483 Cooling Fan Rationality Check Malfunction
# P0484 Cooling Fan Circuit Over Current
# P0485 Cooling Fan Power/Ground Circuit Malfunction
I take my girl to a local tuner so I don't have any decent advice with the codes...
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