Code p1133 for a 2005 chevy trailblazer ls/ oxygen sensor where is the sensor located?

On most vehicles, the sensors are screwed in to the exhaust pipes or exhaust manifolds, usually under the car/truck , in the vicinity of "under the front seat" area. They are usually the size of your thumb, and have a wire going to them.

The 1133 code is for a bank 1 upstream O2 sensor. This means it is the O2 sensor installed in the exhaust system on the engine side of the catalytic converter. On a six-cylinder engine, there is only one O2 sensor upstream, and it is installed in the manifold itself. There is also one downstream sensor that is installed just after the catalytic converter. See picture below for upstream sensor location.



On the 8-cylinder models, there are two upstream sensors, and two downstream sensors. This is because there is an exhaust manifold on both sides of the engine and two catalytic converters, one attached to each manifold. If you have the eight cylinder model, the P1133 code refers to bank 1 upstream sensor, which is serving the odd-numbered cylinders. See diagram below for cylinder numbering.


You need to soak the sensor threads in penetrating oil and use a specially designed socket to remove the part. The socket is available at most auto parts stores for a few dollars. The replacement sensor should have anti-seize compound on the threads. Do not remove this or it will make later replacement much more difficult.