03 sierra 5.3l missing on 2468

ruled out cam and crank sensor since it would have to skip even numbered lobes and only read odd numbered lobes, wiring from ecm was checked with noid light and reference signal test to coils was also normal.

figured it out- jacked up and checked exhaust temp with infrared. right catalytic converter plugged pulled pipe and missing went away

thats what surprised me no loss of power until the display said reduced engine power. I never checked the other side they are a set with the y pipe. the other confusing thing is bank 2 sensor 2 showed it was working starting to think I had back flow to sensor 2 to give it that reading that was close to bank 1sensor 2

fuel pressure stayed above 50psi for an hour after shutting off .I am going to rechck compression after cat to make sure and double check muffler as well

repairs complete-after driving rechecked compression fuel pressure and fuel pressure dropped to 52 psi after 1.5 hrs. rechecked o2 sensor readings bank 2 sensor 1 showed a lean condition so switched l to r and lean condition went to l replaced o2 sensor as well. im thinking the o2 sensor saw a non existent lean condition on r bank and overfueled r bank and with the excesive fuel in r bank with o2 sensor reading lean normally, showed a normal reading when overfueled . I cut the y pipe apart because I found chunks of honeycomb in exhaust partially blocking pipe to muffler. once I had y pipe cut apart I found the catalytic on r side melted and twisted sideways in the tube totally blocking it off. the other thing that is confusing is that at no time diid the mil light come on and no code were recorded

above was me don't know why its under a guru nme

when I saw the piece of honeycomb in the pipe I removed the muffler and pipe and dumped and banged it to get debris out then blew air back through with shop vac on inlet end. o2 sensors were fairly clean and visually looked good. I have owned it since new and never put any octane boost or fuel additive in. other than a broken wire to the bank 1 sensor 2 I have had no ignition or emissions problems. only other repairs other than normal maintenance have been both front wheel bearings ,upper left ball joint, tail gate and left rear outer door handles. definitely weird with no codes and the ecm new something was up since it went to reduced power mode but never threw a code.

Well its been 9 months and 27,000 km and no problems so far, other then a rotted brake line. Still no clue as to why catalyst plugged so quick and why o2 sensor didn't throw a code. If t ever does fail again I will repost