I am getting these codes from my code reader. Where should I look for a problem in the truck?
It's a 96 tacoma 2.7L
180,000 miles
both O2's were replaced 2,000 miles ago

I know the p0141 is an O2 heater problem, so i swapped O2's and still get the same codes. Could all this just be from an old cat?

 

Welcome to YotaTech ... what brand of o2 sensors did you use

 

Thanks for the welcome

They were toyota O2's from the dealer.
I was getting the p0141 before replacing them, and now the p0401 has been showing up.

Around 40k miles ago I blew the head gasket, so I'm thinking maybe all the antifreeze that went through the exhaust had some bad effects on the cat, but I would hate to spend that much money on a repair and still have these codes show up. It's just been sitting for 3 weeks now because it won't pass inspection, very sad to see the truck just sit there getting dusty.:pat:

 

have you cleaned the maf sensor yet ?

 

I had cleaned the MAF a little bit before I had replaced the O2's, but it didn't make any differance. I also cleaned the EGR.
The truck doesn't seem to have any drivability problems either. Starts and runs great. I get about 18mpg around town and 20 mpg highway with 31" tires. The only type of engine mod thats been done to it is a set of Downey headers, other then that it just has a lift and the tires, the rest is all stock.