P0420

nickb2

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#31
Well some improvement but not solved. With new thermostat ECT stays at 195 F constantly. So took it for a drive per the TSB. Finally got the Cat readiness test to pass but on driving home the CEL came back on with the P0420 cude again
God damn it, I hate those P0420 codes
 

nickb2

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#32
Something is not working here.

@dabunk, you have pretty much the best minds working for your solution, and you have stated that everything is new, have a live data capable scanner etc.

I don't want to be the a hole here. But something is eluding you right now.
 

nickb2

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#33
@ this point, I am suspecting a bad ECU or an exhaust leak or you missed a bad wiring harness. Something like that would be very probable.
 
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nickb2

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#36
Pay specific attention to this copy paste.

Diagnostic Aids
The catalyst test may abort due to a change in the engine load. Do not change the engine load (i.e. A/C, coolant fan, heater motor) while a catalyst test is in progress. An intermittent problem may be caused by a poor connection, rubbed-through wire insulation, or a wire that is broken inside the insulation. Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following conditions: - Backed-out terminals - Improper mating - Broken locks - Improperly formed - Damaged terminals - Poor terminal-to-wire connection
 

nickb2

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#37
I once chased an elusive code like that on one of those suzuki's, it ended up being a bad connection to the ECM/ECU.

Be sure to have a good multi meter with good piggy back leads. That is where the most techs f up. They probe with test lights, fat leads, or fat hands.

Once I found the problem, the pins were so rounded, I could reasonably say some one probed that before me.

So @ dabunk, utmost respect, your a wrench, but I guess you have to go back to basics on this car.

I am very hopeful my advice did not piss you off, on the contrary, us wrenches need to stick together.
 
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#39
Thanks nothing p--sses me off most times have found a separate pair of eyes/ears finds the difference. I am trying to learn how to post a live feed of sensors. I bought an Autel scanner which can record and save now need to find out how to get it onto the disk and upload to this site. Please bear with me but keep the comments going!!
 
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#40
Hey Dave - I cant believe we are still battling this cat issue - maybe time to regroup.

A 2006 forenza - this is the beer can looking Catalytic Converter in the exhaust down pipe at engine?
The emissions are NOT California type?
- - The size of that cat looks inadequate to start - well that's academic it is what it is.
I assume the cat and sensors were NOT OEM but were aftermarket?
There are NO other codes, no exhaust leaks, rest of exhaust is there - resonator and muffler not oversized piping...?
Engine data -
The fuel trims are ok? ECT is good, nothing red flag obvious?
and we are getting the o2 readings together for us to look at - correct?
 
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#41
Correct on all counts cat is attached yo ex manifold outlet O2 is in manifold and pipe after cat no leaks rest of system tight and stock. Cat an O2 are all aftermarket but all same results as with stock parts. No California ex single cat system. ECT is good now that I replaced the thermostat. No other codes ever present. Fuel trims look in spec to me but want to record while running and post here for you guys to look at.
 

kev2

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#43
For the head gasket YES it would be a factor as the coolant would contaminate the sensors.... and then we get bad readings....
 

billr

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#45
Are you going to do a "block test" first, using the dye that is sensitive to combustion products in the coolant?