Joining Space Invaders, the personal computer, and perhaps Sputnik in the pantheon of modern technological achievements is the oxygen sensor. Most every modern fuel injected automobile has one or more of these sentinels threaded into its exhaust pipe. Elements inside the oxygen sensor tip measure the amount of oxygen gas in the exhaust, and convert the ratio into a signal that makes sense to the engine computer. The computer uses this signal, along with input from other sensors, to feed the right amount of fuel into the air entering the engine. If all parts are working correctly the fuel, air, and spark balancing act succeeds in ideal combustion! If the oxygen sensor goes haywire, the engine computer can add too much or not enough fuel. Poor fuel economy, lousy emissions, or both can be the result of a spent or malfunctioning oxygen sensor. The good news is an oxygen, or O2 sensor is about as easy to remove and replace as a spark plug.
Loop the Loop
The engine computer already has built in data to deal with engine start and warm up along with running around. This mode is known as open loop. The stored information is similar to the read only memory that tells the Space Invaders always begin their video attack with plenty of aliens – and always find more where they came from. Once the engine and oxygen sensor reach operating temperature the system moves into a closed loop. The oxygen sensor makes like Sputnik in the exhaust pipe, and broadcasts a signal as voltage to the engine computer. In the ideal world of complete combustion, the fuel to air ratio hovers at the point where the most complete burn of the fuel added to the air is reached. This 14.7 parts air to one part fuel ratio is known as stoichiometric. If an oxygen sensor goes wonky it can send the wrong signal. Too much fuel and the engine runs rich. Too little fuel and the engine runs lean.
Oxygen Sensor Check Remove and Replace
- Engine Code Reader or Multimeter
- Hand Tools
- Oxygen Sensor Socket
Remove and Replace
Fuel economy can suffer if an engine is running too rich. An engine that is running lean can run down on performance and experience internal damage. A foul running engine can also ruin the catalytic converter, a far more expensive part than an oxygen sensor. The same engine computer that makes things run right also knows when things have gone wrong. A malfunctioning O2 sensor is one of numerous faults that can trip the Check Engine Light or throw a malfunction code. While every vehicle made after 1996 adheres to a standard known as On Board Diagnostics II (OBD-II), cars and trucks made before 1996 are not so standardized. Adding to the confusion is that some automobiles can have four or more (!) O2 sensors. Removing and replacing a bad oxygen sensor is a matter of lefty loosey and righty tighty. Removing and replacing a good oxygen sensor is not going to solve any problems. A code reader or voltage multimeter can help sniff out the bad ones.