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PO420 Code - Catalyst Efficiency Below Threshold, (Bank 1)

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That code is a bad oxygen sensor. Bank one is located at the manifold. Remove and replace this sensor and the code will go away.

Posted on Sep 11, 2010

  • thecranks Sep 16, 2010

    i want argue but po420 is not a o2 code it is exactly what it says cat effiency set by the pcm using data gathered by the o2 sensor to determine that the ppm seen by the downstream o2 is to high and the converter is not performing up to standard and is usually caused by an underlying problem ie sparkplugs,clogged fuel filter intermittent misfire from bad injector that almost never sets a trouble code and so on i,m just saying cover the basic,s first

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If a good tune up has not been performed then start there then do a cat burn off procedure where you short one cylinder and run engine @ 2500 rpm for 10 minutes this allows the cat converter to be super heated and burn off any contaminates once done the car will have to be hooked to scanner to turn out light

Posted on Sep 11, 2010

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  • ibjiggrd Oct 09, 2010

    How do you "short" one cylinder?

  • thecranks Oct 09, 2010

    remove one of the coil packs mounted on each sparkplug do not remove the sparkplug just take the coil pack off the plug insert a sparkplug into the coil pack and lay on the engine start and run at 2000 to 2500 rpm once done remove plug from coilpack re-install back in place

  • thecranks Oct 09, 2010

    see added comment

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Where should i find this sensor P0342?


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).

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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

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What do these codes mean ? po430 po420 po306 for mercury cougar 1999


P0430 code is(catalyst efficiency below threshold on bank 2)
P0420 code is((catalyst efficiency below threshold on bank 1)
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Code of PO174 1 system too lean (bank 1) Code PO420 Catalyst efficiency below threshold (bank 1) Code PO430 Catalyst efficiency below threshold (bank 2)


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

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What does code po420


P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)\
This means that your bank 1 catalytic converter is not doing its job, or the O2 sensor system monitoring it has an issue.

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Servise engine soon code po325 or po420


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The PO420 means that the Catalyst System has an Issue'

The actual error is

"Catalyst system below Threshold (bank 1)"

As mentioned above, the code's description is Catalyst System Efficiency Below Threshold (Bank 1). OK, now tell me that again in plain English please.... let's break it down: the catalyst system being referred to is your three-way catalytic converter; so the catalytic converter is not working properly (i.e. it's not efficient). Bank 1 refers to the side of the engine which contains cylinder #1. On inline engines such as 4 & 5 cylinder engines, there is only one bank. So, to really simply things let's just say that the efficiency of the catalytic converter and/or exhaust pipe and/or O2 sensor is not so great.

There are a number of things that could be causing this p0420 catalyst efficiency code. The most common thing is the catalytic converter itself is no longer functioning properly. The other likely thing is the rear O2 (oxygen) sensor is no longer working properly. Other things could include exhaust leaks, damaged exhaust pipes, damaged O2 sensor wiring/connectors, plugged catalytic converter, etc.

You can search for the Information on the web. Just type in the actual error above into you fav search engine!

Hope that helps...

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