so last summer I had 3 or 4 codes pop up and all were 02 sensor related. Turned out my fuel pump was bad. So had that replaced with an ac delco one. After that got done my SES light was off for about 50 miles then came back on. So i cleared it and it stayed off. But ever sense then, whenever i smash the pedal to the floor for a period of time, my light comes on, and it reads as low voltage to the 02 sensor after the cat. This sensor measures cat efficiency correct? If I clear the code off itll stay off for months, unless I put the pedal down. I took the sensor off and have cleaned it several times. Whenever i use the scan tool i check the readings of the 02 sensors and all have the same activity numbers. So what is causing this? Partially clogged cat, or is the sensor just bad? The truck runs good, occasionaly hesitates if you give it heavy throttle out of a turn, but otherwise fine. This sensor doesnt really effect engine efficency right?

 

No that sensor won't effect engine performance however if your cat is bad then that would. Have your tried cleaning the maf sensor and egr?

 

if my cat was bad wouldnt it run really bad and cut in and out? MAF was replaced about 8 months ago with a reman. Havent touched the egr

 

I would say check out the egr, then do a fuel pressure and leakdown test. If those come back good I would look into a new cat. You can get a hi flow pretty cheap on ebay then do the spark plug non fouler trick with the down stream o2 sensor so it won't throw a code on you.

 

It appears I dont have an egr because my truck was made in the mid 02s. Any other suggestions on what this may be?

 

I would still say there is a good chance that the cat is bad. You can get a cheapo and have it welded on then do the spark plug trick so it won't throw a code. Or do a fuel pressure test first, may have a bad regulator. Do you have the code its throwing?

 

Whatever the code is for the downstream 02 sensor that reads low voltage. Today I drove for about 30 minutes straight in the heat and i really felt like i was loosing power. Would a bad cat be more noticeable after a long period of driving time? I also noticed my temp guage was higher then normal, usually it runs a touch under 210 and today in the heat it was exactly at 210. My cooling system was recently serviced with a new thermostat, coolant flush, and the LIM gasket was recently replaced.

pretty sure the code is P0137

 

Does the cat rattle, look discolored or smell like rotten eggs out of the tail pipe? If so, the cat is plugged. How has your mpg's been? Loss of power and poor mpg's are signs of a bad cat among other things. You may also have a bad coolant temp sensor since you have had the rest of the cooling system worked on.

 

Funny you mentioned rotten eggs. Whenever I start it in auto with the bay doors closed it occasionally does smell like that. If its plugged can you try to blow it out? Or do i just need a new cat?

 

I would just buy a cheapo universal hi flow off ebay and weld it on. Then raise up the downstream o2 sensor with a couple of spark plug non foulers.