420 code catalyst system efficiency below threshold (bank 1). EGR replaced along with both upstream and downstream 02 sensors on bank 1. Check engine light keeps coming on.

Got it scanned and it's P0420: Catalyst efficiency below thresholdbank 1. They said it could be a bad catalytic converter or oxygen sensor. I borrowed a scanner and tried to measure the oxygen sensor readings over time.Sep 8, 2011


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P0420 Error Code: Catalyst System Efficiency Below ...

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P0420 OBD-II Trouble Code. Technical Description. Catalyst System Efficiency Below Threshold (Bank 1). What does that mean? This diagnostic trouble code ...

P0420 Code Fix How Its Done Catalyst Efficiency Below ...

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EXHAUST RELATED ERROR CODES

There are 711 possible PO generic DTC error codes. Only 7 of the 711 codes are exhaust related.

PO401: Insufficient EGR Flow

PO402: Exhaust Gas Recirculation (EGR) Excessive Flow Detected

PO410: Secondary Air Injection System Malfunction

PO420: Catalyst System Efficiency Below Threshold (Bank 1)

PO421: Warm-Up Catalyst Efficiency Below Threshold (Bank 1)

PO430: Catalyst System Efficiency Below Threshold (Bank 2)

PO431: Warm-Up Catalyst Efficiency Below Threshold (Bank 2)

THINGS TO ASK YOURSELF OR YOUR CUSTOMER

Have there been any driveability or performance issues with the vehicle, have there been any recent repairs or tune-up work performed, if so was the check engine light reset and were the codes recorded on previous repair orders.

Do not rely on scan tool data alone. In most applications, the customer will have the check engine light reset prior to repair. If the original cause of converter failure is intermittent, only the catalyst failure code may show up (masking the original reason for converter failure).

hi,my friend, you can try,

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

P0420 = Bank 1 catalyst system efficiency below threshold. This DTC (Diagnostic Trouble Code) is set when the O2 downstream sensor indicates/measures the amount of hydrocarbons/oxygen present in the exhaust after it passes through the converter. When this sensor detects exhaust gasses identical/near identical to the upstream O2 Sensor (the actual gasses at the exhaust port - before the converter), it will set this 'efficiency below threshold' code. The catalyst has failed to 'convert' the exhaust gasses to CO2 + Water.

Wow!, I answered this about 30 minutes ago, but somehow my answer didn't post.

Fault code 420 is Catalyst system efficiency below threshold, ( bank 1 )
Fault code 430 is the same as above but, ( bank 2 )

Fault codes do not determine what part is bad, they just reduce the field for troubleshooting.
This is what I would have checked;
1. Oxygen sensor, upstream ( meaning before the catalytic converter )
2. Oxygen sensor, downstream ( meaning after the catalytic converter )
3. MAF, ( mass air flow ), sensor
4. Idle air control sensor.

Your problem will be with the emission system.

I hope this helps you.

If the engine is a V6 (2.7 or 3.5 lit), bank 1 is next to the firewall (right hand) when facing the back of the engine.
If the engine is a 4 cly (I4), there is only one bank and is designated Bank 1 (exhaust manifold).

The catalyst to which the code refers is the UPSTREAM, and there is only ONE upstream cat for any bank.

Clue: Two upstream O2 sensor and two downstream O2 sensors - one before the CAT and one after the CAT. the downstream O2 sensors are identical to their upstream sisters. The only reason for the DOWNstream sensor is to monitor the CAT efficiency (threshold).

The catalyst on either bank is essentially the exhaust manifold which houses the CAT... it is the only CAT to which the code P0421 applies.

Hope that helped

P0430 Catalyst System Efficiency below Limit - Bank No 2" How would I fix that without taking it in? P0430 - Catalyst System Efficiency Below Threshold (Bank 2)
you need a scan tool to monitor the upstream and downstream 02 sensors on bank 2 more than likely its the converter. also check for exhaust leaks before converter . Most times the problem is the Downstream O2 sensor is defective.

One of three (3) possibitlies:
1. Catalytic Converter is malfunctioning.
2. O2 Sensor is malfunctioning. This will be the O2 Sensor located on the Catalytic Converter. However you should check and/or replace both sensors if needed.
3. You have an Exhaust Leak.
In Order of checking:
A. Check and Repair any Exhaust Leak.
B. Replace the O2 Sensor on the Catalytic Converter 1st. Also Known as the Downstream O2 Sensor or HO2 Sensor.
C. Replace the O2 on the Exhaust Manifold prior to the Catalytic Converter. Also Known as the Upstream O2 Sensor.
D. Replace the Catalytic Converter.
Let me know if this helped, or if you have any additional information, problems or questions. Feel free to contact me at FixYa.com!

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

There is one 02 sensor in front of the catalytic converter (called upstream), and one behind it (downstream). When the engine is warmed up and running normally the upstream oxygen sensor reading fluctuates and the downstream one is fairly steady. In the case where both readings are fairly steady, a P0420 check engine light code is set.

Possible Causes:
Oxygen (O2) sensor not working correctly
Damaged or leaking exhuast (pipe, manifold, catalytic converter)
Damaged catalytic converter

MAP sensor, Maybe, but doubt it.

When the misfire monitor detects a misfire, it will trigger the check engine light with the specific cylinder number as the last digit in the P030X code. For instance cylinder 1 misfire is P0301, cylinder 2 is P0302 etc. In this case we are left with a P0304 in the computer memory. Which is cylinder 4.
Possible Causes:

Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns: leaking EGR valve or restricted ports
Base engine concerns: low compression, valve train problems and timing issues
Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issues
This maybe causing PO420 code to go off.
Which is:
P0420 Catalyst System Efficiency Below Threshold (Bank 1)

There is one O2 (oxygen) sensor in front of the catalytic converter (called upstream), and one behind it (downstream). When the engine is warmed up and running normally the upstream oxygen sensor reading fluctuates and the downstream one is fairly steady. In the case where both readings are fairly steady, a P0420 check engine light code is set.

Possible Causes:

Oxygen (O2) sensor not working correctly
Damaged or leaking exhuast (pipe, manifold, catalytic converter)
Damaged catalytic converter