Seized O2 Sensor

The engine light is on, got to get it fixed before we can get the Truk inspected.  My OBDII Code Reader is giving code 1155.  The manual for the Code Reader says that the "Rear Main O2 Sensor Signal Faulty".  OK, what does that really mean?  There are three Oxygen Sensors on the Truk (V6).  One is right up front between the motor, and the radiator, on the exhaust manifold.  The second, under the car, between the motor, an the firewall, on the exhaust manifold.  The third is downstream behind the Catalytic Converter.  So the Code Reader Manual says rear, so I figure the one on the back of the motor is the one that needs to be changed.  I was able to change it, although it was difficult to get to, on my back, under the Truk.  But it didn't clear the Check Engine Light.  I started searching for better definitions for the ODBII Codes.

My best tool for working on cars now is the interwebs.  So, I found out that code 1155 is the Oxygen Sensor on the Second Bank of the motor, which is the front bank, and code 1135 is the Oxygen Sensor on the rear bank.  So, I changed the wrong sensor.  The plan at this point was to replace the front Oxygen Sensor with the one I removed from the rear.  This is where I had a kink in my plans.  The front Oxygen Sensor was seized in the exhaust manifold.

The rear Oxygen Sensor was tough to break loose, but easy to turn after that, finger tight.  The front Oxygen Sensor broke loose, then was totally stuck.  There are a number of specialized tools for Oxygen Sensors that are all 7/8 inch.  First its the wrong size, the nut on the Oxygen Sensor is 22mm.  Plus open ended wrenches are not going to work in a seized bolt situation because they stretch when you put a lot of torque on them.  So the specialized Oxygen Sensor Wrenches are out, and the open ended combination wrench was out.  They only rounded off the corners of the nut.

In order to remove the Oxygen Sensor I literally had to break it off.  I used my Blacksmith Hammer, and an Iron Bar to break off the stem of the Oxygen Sensor.  Its a metal tube with a ceramic interior, so you'll crack the ceramic by hitting it, and de-swage the metal tube from the nut part of the sensor in the exhaust manifold.  With the stem removed you can then use a regular 22mm, 6 point, 1/2 inch drive socket, and a heavy duty driver to force the remaining part of the Oxygen Sensor out of its hole.  I also had the Blacksmith Hammer to move the socket driver.  This sensor did not want to come out, and it took some threads with it.  The Oxygen Sensor was literally welded to the treads of the Exhaust Manifold.  After getting the old sensor removed then I had to deal with the damaged threads.  There is a tool called a Thread Chaser which is a specialized Tap which will clean up the damaged threads.  Its in the Tool picture above, on the right with the Anti-Seize Compound.  You could also use thread cutting oil for tapping the threads.  So I ran the Tap in, and out a few times, then the new sensor went in easy, and sealed, the threads are saved, Yay!  The Check Engine light went off the second time I drove the Truk.  That was a good project for a rainy weekend...