Replacing a seized sensor – DIY thread repair (P0158)

CARspec had a 2007 Lexus RX350 with a check engine light on today, Code P0158.  Diagnosed as a failing Bank 2 Air/Fuel ration sensor, the technician went to replace the failed unit only to discover the sensor seized into the exhaust manifold.

This is a common problem for MN owners – corrosion builds in the threads and locks the sensor into the exhaust manifold.  In this case, the technician alternately loosens, applies penetrating oil, and tightens the sensor, progressively working the sensor out.  Once removed, it looked something like this:

On bottom is the old sensor.  Note the threads are damaged beyond repair.  On top is the new sensor for comparison, and resting on both is the tap used to repair the damaged threads in the manifold.  The tap acts like a special cutting bit, threading into what remains of the damaged threads in the exhaust manifold, repairing the threads as it cuts into the Lexus’s exhaust manifold, prepping them for the replacement sensor.

Here the tap has been threaded partially into the manifold.  The technician turns the tap in the manifold 360 degrees and then removes and cleans the tap of metal debris and applies more penetrating oil.  By being patient and keeping the new threads clean as they cut the technician ensures a proper seal for the new sensor.  Here is what new threads looks like after being cut and cleaned:

Although a bit more rough than the original, the new sensor threads in easily and is torqued to Lexus’s specification:

The new sensor is verified via the scan tool as working and the vehicle is returned to service.  By being patient during the removal and tapping of new threads, the technician has saved the owner the hassle and cost of replacing the entire damaged manifold (in this case at no additional charge to the owner).  As Eden Prairie and Chanhassen’s Toyota and Lexus repair specialist we are happy to offer this service that many an auto mechanic would replace the entire manifold for, repairing the damaged threads to respect the guest’s budget.