Is my O2 sensor shot?

Here's a long story short. I have a 2000 tacoma 4x4 2.7L regular cab. My muffler was shot so I bought a new one. The wrong one. I bought for an extended cab instead of regular cab. Right engine, wrong cab.

Anyways,... for whatever reason I thought that the new muffler was only about 6 or so inches longer then the right one. Because when I take off the one cat to get the muffler on the truck the muffler hangers are about 6" farther than theones on the truck. ANYWAYS!

After hangin the exhaust with clothes hangers temporarily until I figure something out I went driving. The CEL came on. Great. I then find out that I wasn;t suppoe to take off that cat. So i cut and weld the muffler piping shorter and reinstall the cat. Everything isd perfect now. But after pulling the battery neg,... the CEL came back on.

So I took it to a AutoZone and had my codes pulled. The only code returned was a P0125. Is the O2 sensor at fault? My gut feeling says yes. seeing I had no problems prior to the muffler/ cat mishap. But I just dont want to go ahead and start replacing stuff.

The AutoZone slip witht eh code info said, "Engine coolant temperature", or something like that, "is always low." It listed,...

Probable Cause:
1. Faulty thermostat
2. Low coolant level
3. Faulty ECT

So what do you think? I read somewhere that the O2 sensor could cause this code. But im not sure how accurate that info is. Whats up? Thanks.

 

Do some research online about the code itself.

If the code says its NOT the 02 sensor, then...chances are...it's whatever the code says it is.

Taken from internet
This means that the engine coolant temperature (ECT) sensor indicates that the engine has not reached the required temperature level to enter closed-loop operation within a specified amount of time after starting the engine.

www.google.com is your friend!

 

I'm just going to change the O2 sensor.