Sorry to reopen this thread but didn't want to start a new one dealing with same issue.

I have 99,100 on my 2001 1500.......it runs fine, doesn't miss. It has a check engine light on and get terrible mileage. What other symptoms should you have if the 02 is bad?

I'm only going to be able to change one now and one later, which one is the most important one?

 

See what codes it has. You should be able to do the key dance to pull codes. Cycle ignition on/off three times. On the third time, leave it on. DO NOT start the engine. Codes will display on the odometer. Write 'em down.

Pre-cat O2 is the most important.

 

WAltom,

I am a product specialist with Walker Products, a manufacturer and worldwide distributor of oxygen sensors. The symptoms of a failing oxygen sensor do include poor gas mileage, as well as increased emissions, hesitation or stalling, and others. At 99,000 miles, it would be a good idea to change your sensors. However, a CEL stemming from an O2 does not absolutely mean that your O2 sensors need to be replaced. As HeyYou said, try to get the code(s) from your vehicle. Find out what your engine is trying to tell you.

 

I got the codes......P 1281..........what does that mean?

 

P 1281 is engine too cold. Your thermostat maybe stuck open. If you are new here checkout the free Service manual. It has a section that details all of the codes and gives you trouble shooting tips. Welcome to DF as well!

 

Engine too cold? How do you clear the code to see if it's still having that problem.

 

If it has the code, replace the ECT to start diagnosing the problem. Get a Haynes too. And a cheap DVM. With both of those , you can test almost all the sensors.

 

What is your temp gauge telling you?

 

On a 90+ day it runs about 190 -195 as it always has...........on the way home the other night when it was pretty cool out, it might have gotten to 160.

 

Replace the thermostat.