P0420

dabunk

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MAKE:suzukt
MODEL:forenza
YEAR:2006
MILES:130K
ENGINE:2.0
DESCRIBE ISSUE.... Car throws this code cat efficency low Replaced cat and O2 Drove 2 days and code came back Any ideas or suggestions? No scanner to monitor O2 activiy
 

kev2

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Hey dave -
Without knowing what the pre and post cat o2 readings the PCM is seeing I can only 'guess' a likely scenario.

I would guess that the cat is getting some mixture it cannot clean up.
There is a wiring problem. Maybe a defective o2 sensor. Exhaust leak. coolant or oil entering cat. Engine ECT. Really cheap replacement cat.
Any active codes or known issues ?
My tag line is it stock, no modifications.
Maybe a fuel inj leaking.

Sorry just possibilities guessing what the PCM is dealing with is a guess.
 
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billr

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You should be able to monitor those O2 sensor readings with a couple of simple voltmeters and long leads. Not nearly as easy as live-data, of course, but entirely "doable".

Did you do a "smoke test" for exhaust leaks after the cat was replaced?
 

nickb2

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I think the key here is knowing if the o2 readiness monitolrs and appropriate drive cycles were done after repair of the cat and o2 sensor.
 

kev2

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Checking monitors will require a SCANNER -
unfortunately a scanner is a must have these days.
My point file and dwell tools not so much.
 

dabunk

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OK now have scanner to monitor O2 Replaced downstream O2 as well to know all is new. Have put over 200 miles on car and code still sets. As I monitor both up and down while running they bounce up and below 500 In the old days we looked at O2 crosscounts and they seem to be functioning perfectly. But if I clear the code do a cold start and drive both stop and go and highway within 25 to 30 miles the code sets again. OK where to go from here?
 

billr

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How about the leak test on the exhaust, was that ever done, using smoke or soap-solution all over?

What frequencies are the O2 sensors "bouncing at"? A graph would be nice, but just an estimate is better than nothing.

Have we asked where fuel trims are sitting?

How long does it take to go into closed-loop?

Does anybody have an FSM for this vehicle? We need to know the specific sets of conditions that can set the code.
 

dabunk

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OK got time this week to get back to this. Remember I am diesel tech car tech poor. Drove car 20 miles pulled in and chr=ecked at idle short term fuel trims reading betwen 0/1/2 long term fuel trims reading a steady 2 and code p0420 had reset during the drive. Next step?? Thanks
 

kev2

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Hey Dave ;
I am confused -those fuel trim readings 0/1/2 ? could you translate to what I am used to - something like STFT +2 , LTFT +2....
Don't forget to give us ECT, IAT, B1S1 o2 voltage, then post B1S2 voltage....
The manual I will try to get, right now pretty generic.
"and the PCM detected the HO2S-12 and HO2S-11 signals were too similar." I know useless give me some time to get manual

GTG
 
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kev2

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There are some conditions in the TSB I posted above post #5 -
still looking
 
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