My 2000 Express 5.7 is giving codes 0137 and 0452. It is getting really poor gas mileage and the tailpipe is really black. I replaced the fuel pump last fall and the tank pressure sensor (0452) along with it. The 0137 is the downstream O2 sensor and should not affect mileage from what I understand. It was very sluggish including when cold so I sprayed B 12 Chemtool into the MAF while running. After that it had so much power it lit up the tires. It is better now but still gets poor mileage and after clearing the codes, the idiot light came back on in short order. The last time that I replaced the fuel pump, I had to siphon out the fuel and in the process, I bent the silver flap in the fuel filler neck. Could that give the code 0452? I never had a code for the MAF and I have never run an aftermarket air filter so I am really scratching my head as well as paying through the nose with gas prices and the bad mileage I am getting.
