Noisier exhaust and P0420 After tranny removal...

[Mexplorer]

Well, i had my tranny repaired due a leak in the bellhousing (it was the front pump seal) and was in the shop 2 days. Before that, i was getting ONLY the P0401 , which i think is for a bad dpfe sensor. After the transmission repair, i noticed a strange noise in the exhaust system; it was louder. I left the shop thinking it was a normal thing. Yesterday i plugged my code reader and got two codes: the habitual P0401 and now a P0420, which i know what it means.

I did a search in the forum for this code, and all the people recommends changing the 02 sensors. But i know these are very strong units and they arent prone tho fail easily, so i have read multiple stories about changing perfectly working O2 sensors, fixing the problem for a week or 2, and getting the CEL again for the same thing.

Maybe the mechanic installed improperly the exhaust system when he removed the tranny ? I went to ask to the shop about this, and they said they removed some carbon buildup in the exhaust system when they were working in the trans, so that is why my truck is louder ??

The only thing i suspect for the noisier exhaust is this connection after the rear cat and the muffler. When i put my hand over this, i can feel the air coming, so, do i need to tighten more the 2 bolts ? i attached a drawing from the repair cd manual.

If you have pics of a stock exhaust system, would be very appreciated.

How do i get rid of the p0420 code ? i erased it, seeing if it comes back.

My truck only has 99,000 miles. Is a V6 1996 OHV.

 

[91exploreron37]

U need to replace that gasket(13) that goes in between the connections and then retighten. Make sure they plugged everything back up correctly as well.

 

[Mexplorer]

Thanks for the reply. I removed the muffler from the cats and saw inside....it looks clean, or at least i think so. No carbon buildup or something similar. I checked the 02 sensor near the end of the cat, and cleaned a little bit, but it was looking good. Well, i reinstalled everything, tighten the bolts, but no luck, the sound didn`t change too much, and the code P0420 appears now like a "pending code" , but my code reader says the catalyst monitor is not complete, so i think i`m getting this code again when the monitor completes.

Tomorrow i`m going to try to remove the entire exhaust sistem to check for leaks. Im very mad at the shop who did the tranny repair because of this. Im pretty sure they screwed something. But well, i cant do anything. Is there a way i can test the O2 sensors . I only have a poor quality code reader (or at least i dont like it a bit....) and here in mexico we dont have autozone or some place that read codes for free with a scanner. Feel free to recommend to me something.

 

[BIGHVM]

After fault that you fixed that generated the codes, you should unhook the battery to reset the ecu, or it will remember the fault codes and they will show up again even if you have fixed the fault- take the batt connections of for half and hour and then re attach. drive the car for a few hours total time and then code read- that is the only way to know for sure if you have fixed the fault or is still exists.