The engine control unit (ECU) on a Chrysler 300M uses a pair of oxygen sensors located on the exhaust to help determine how efficiently the engine is running and adjust the air/fuel ratios accordingly. When these sensors go out, it triggers the "check engine" light. Replacing the sensors will fix the light, as well as make sure your engine runs correctly.
Raise the 300M using the jack and set it down on four jack stands, one on each corner. Crawl underneath the car and locate the oxygen sensors. These are three inches long, with wires running out the ends. They are located on the exhaust, one on each side of the transmission.
Unplug the electrical connection to the sensor using your hands. Remove the oxygen sensor from the exhaust using the oxygen sensor wrench, then discard the old sensor.
Apply anti-seize compound to the threads at the end of the oxygen sensor, then install it into the exhaust tubing. Install it first by hand, then use the oxygen sensor wrench.
Repeat Steps 2-3 for the remaining oxygen sensor if necessary. Lower the 300M off of the stands and set it on the ground using the jack.
