Hello everyone!
Here's what I am facing. I had the trans replaced recently at a reputable..uh hum...shop. When I got my Blazer back, it no longer had the glorious Green light go ready status on my Innova scanner. In fact, everything was lit up like a Christmas tree! Well, I traced it to a vacuum leak for the 4X4 actuator under the battery box. (Deleted and now going to install a Posi-Lok-Cable to once and for all eliminate this retarded device!) Ugh,
So after I plugged the vacuum line to the actuator, everything pretty much cleared up except that the "HTR" is still flashing and I have a yellow light status.
Here's what I just found...a cracked air intake tube in between the MAF and the Throttle body. I can't believe this moron didn't take an extra minute to undo the connection of the air tube at the throttle body. My guess is when they dropped the trans, it pulled hard enough on the air cleaner assembly and ripped the air tube, thereby creating a lean condition at WOT.
My Blazer has since been bucking on take off but cleans itself out after it gets going. This really made me mad cuz I just installed a new cap, rotor, plugs etc and thought maybe some serious stuff was going on.
Okay so here is the ultimate question, do you think a lean condition that is being induced from a broken air intake could cause the O2 Heater cycle to not complete thereby causing this heater code issue. It is not throwing a code per say, just flashing "HTR" on the scanner....
Thoughts?
Oh, and you can bet your *** that the shop is going to pay for a new air intake in the morning and weld the cat bracket that now squeeks like hell going down the road cuz the moron stripped the bolt holes in the crossmemeber!
$1700 later for more headache! SMH!

 

Well, The Blazer is no longer bucking or surging on take-off. I replaced the air intake tube with a good one from a pick a part place for 5 bucks.
I took the truck back to the trans shop and they tightened exhaust collector by repairing broken stud properly.
So, no more P0420 code pops off but I am still getting a O2 HTR code flashing.
(Again, wasn't doing this prior to trans job)

Now Bank 2 LTFT much more pronounced than other side and STFT readings are about the same across the banks. This leads me to the Bank 2 side so tomorrow I will pull plugs and see what they look like. Could have a bad Denso plug or a bad wire...
From there, I will double check the exhaust connections on bank 2 side before cat.
After that, I will scratch my head again! LOL

 

If you have over 40,000 miles on those O2's replace them all.

 

So after driver side manifold was fixed properly and tightened accordingly, the P0420 code has not been back! I will try to tighten the psgr. side exhaust to verify collector is tight. Small leaks can cause this and after trans guy lost his attitude, as a result of thinking I was asking him to change O2 sensors for free, he listened to me and learned something. Even though blah blah he worked for a Gmail dealership back in the day yada yada.
The only thing that changed from green light status till now has been exhaust opened up etc. For trans change.

 

I noticed a miss the other night while I was driving in fog. Put new plug wires on and fuel trim got better. Still have i/m readiness looking for htr....probably going to clean mafia next.