sd2734

The MIL came on and the codes are P0426 "Catalyst Temperature Sensor Range/Performance Bank 1" and P1126 "Thermostat Operation". I cleared the codes and the check engine light went off. After a test drive, once all the tests were run, the MIL came back on with only the P1126 code!?!
The Sentra is 2001 GXE with approximately 63k miles. Any suggestions or similar problems/solutions experienced before?
Further, I consider replacing the Thermostat to see if the P1126 will go away. The temperature gauge acts normally (stays close to the center once the engine warms up)
Is the thermostat located at the end of the upper radiator hose or the lower hose?
Also, what might be the reason for a P0426 code appearance? Before replacing O2 sensors or Cat converter I want to know if they are faulty. The dealer tells me that there are 4 sensors at $137 a pop!
Thanks for your help,
Simon

sd2734

Did anyone had these 2 codes together at a time? I start to think that the O2 code P0420 might've been on because the Thermostat was malfunctioning and therefore make the engine run cold and increasing the emissions...
Does that make sense or it is sci-fi?
Thanks to all!

FRAG1

I also had a engine check light come on. I had it checked and the code said P1126 code. im confused since they told me where I had it checked that it was the "Throttle Control Motor Relay Circuit open or shorted. I have also read online that its the thermostat. so which one is right? I would hate to start spending money chasing a problem all over the car.

if it is the motor relay circuit is there any danger of the car speeding up on its own? thanx: