Interesting P1135 issue, Could definitely use some Toyota experience

So I picked up a 2002 SR5 2wd for my son a few months ago. Has been running fine until about a week ago. Started running rough and getting bad fuel millage. No CEL but I ran codes anyway. (Think my CEL may be burned out) it's got a p1135 p0306 as well as a random misfire code. It's a Cali spec apparently so no biggie replace the AF sensor right, easy day. Well apparently the previous owner cut the exhaust foward of the sensor and cat an welded a new straight pipe to the muffler. No bungs for the AF sensor or rear O2 sensor and the sensors are not there. What I really don't get is how this thing ran fine before and why is it running like crap now. And of course what the best remedy for my situation? Idk if it's possible to throw a computer tune at it or what. Could really use some advice. Thanks

 

I'll bet money the scumbag prior owner pulled the CEL light for a quick sale.

Remember people, if you are shopping for used cars without a code reader, you are going to have a bad day.

There are ways to rig up and fool the computer and return a constant AF value. I have never done it.

 

Yeah I 100% believe this was the case. If anyone knows the ways of the Jedi to do what your talking about I would love to know.

 

Follow up if anyone might be interested. Since the other sensors have been missing for what looks like a long time, I started running down the usual suspects of misfires. Reset the codes and ran it again, got a MF on #6. Found a spark plug boot with holes and electrolysis tell tales. Replaced spark plugs wires and she runs great. Easy day.

 

Cool and yes, everyone is interested in followups.