PO420 code issues.

[Bob Brown]

I have a 98 Explorer sport with the 4.0 SOHC engine and 100K mileage. Have replaced the plugs and wires. I have a PO420 code that keeps coming up. Disconnect the battery and reset code and all is well for a time. Passed the NH emissions test with no problems. Engine ran fine and reved to full red line. Code comes on and engine runs sluggish. Has hard time revving over 3500. Gas mileage drops. Reset code and runs great again. Doubt this is a bad converter as I can reset code and it runs fine again. Any idea's? Anyone know how much Ford dealer would charge to remap PCM?

 

[BrooklynBay]

Welcome to this forum! I've moved this thread to the EEC-V section for you.

 

[Turdle]

Bank 1 ( passenger side) cat below efficiency.

Could be the catalytic converter, or, the 02 sensor used to monitor it

I would do this.
First, check for an obvious exhaust leak.

Second, switch the 2 rear 02 sensors with each other. be sure to swap the plug connections also. Then, reset the pcm.

If the code changes to another, as in reporting a bank 2 cat fault,--you have a faulty 02 sensor.

If the code remains the same, the catalytic converter is bad.

There may be a slim chance that changing the sensors will resolve the issue, especially in the off chance there was just a bad connection in the connector.

Oh--while you are looking at the connectors, make sure one of the pins hasn't been shoved out of the holder by a connection attempt. ( plugging it in at a wrong angle)

To access the rear o2 sensor plugs and actually be able to see them, I remove the center console. It really is easiest--

http://www.explorerforum.com/forums/showthread.php?t=209771

this is what you see after removing tha console-
the green and blue plugs are the 02 sensor connectors

The socket is on the 02 sensor location. My rear 02's have been switched off thru tuning, and there is just a plug there, but the picture shows location for you.

 

[aldive]

P0420 OBD-II Trouble Code
Technical DescriptionCatalyst 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.



SymptomsYou will likely not notice any drivability problems, although there may be symptoms.

CausesA 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 SolutionsSome 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
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

 

[L2fish]

PO420 code

I am also getting this code in my 1996 4.0 Explorer now that I have replaced my thermostat and the engine is reaching normal operating temperature. My exhaust gasket right after the cat is gone. Could this be causing the code?