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I'm now getting 16556(fuel trim too rich) and 16806(catalyst). I hooked up computer with VCDS and did some test relating to oxygen sensor, MAF and catalyst. Here's the problems:(engine is at normal operation temperature and cooling system works good)

Block 002: MAF data shows around 5g/s(between 4.6 and 5.8) at idle. So assume that the MAF sensor is good.

Block 030: the first window shows 111 and the second shows 110 all the time. I read some thread says that in order to perform a o2 sensor/cat test, this should be both 111 or at least pertinently both 111. But some others says that the second windows should be 110. I'm confused about this.

Block 032: the first window(Additive fuel trim) shows -18%and the second window shows like -17.2% something.

I tried to perform cat/pre-cat o2 test by entering basic-settings, block 034/036/046. Tried to rev up to 2500rpm the test still doesn't begin. Suspecting that the rear O2 sensor might be wrong(because of that 110). Is this suspecting right?

Note: The MAF, front O2 sensor are both new so they should be fine. I didn't replace the rear O2 sensor because I don't think it cause problems but now seems I have to replace it...Car has 116600 miles but it experienced misfire some time ago so suspect that cat is already bad...Just wanna fix the rich fuel trim because it's been eating gas....
 

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Discussion Starter #2
Update

Today I tried to do an oxygen sensor and catalyst converter aging test. I followed the manual, entered Engine, selected 04-basic setting, block 034, it shows TEST OFF on last window, the second window shows cat temp 400C, I pushed gas to 2500rpm and holded for more than 10 seconds but the test still doesn't start. Also I tried block 046 which is the cat aging test the same thing. I took a look at readiness it showed that the EVAP system not ready and cat not ready. Readiness code shows 0000 0101. Does it mean there is an EVAP problem? There is no EVAP related codes. If there is an EVAP problem how can I diagnose?
 

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You can check the related fuses to the purge valve. You can inspcet the hoses connected to the EVAP canister. If the pump on top of the canister does not pressurize the EVAP system, it should trigger a dianostic code. There should be some hoses that come frome the purge valve that go to the intake manafold or the throtle body I would think. You can look at them too . Ther is nothing to plug up, all that goes through this system is gas vapors. I have never heard of an EVAP system failling, Does'nt mean it can't. Maybe the valve is bad. When the engine is warm maybe youcan hear it clicking or feel it cycling. I don't know if they can be checked.
 
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