​Oxygen Sensors that have been around for more than 20 years, yet most motorists do not even know they have one or more of these devices on their vehicle – let alone what it does.  Sometimes the only reason a vehicle owner becomes aware that they have an oxygen sensor is when the vehicle fails an emissions test or is consuming too much fuel.  But in most cases mechanics will not have a clue as to how to diagnose or test this mysterious little device that is often blamed for all kinds of drivability and emissions ills. An O² sensor monitors the fuel mixture so the engines computer can adjust the air/fuel ratio to maintain the lowest possible emissions and best fuel economy.  The O² sensor does this by reacting to unburned oxygen in the exhaust.  It acts like a rich/lean switch that signals the computer every time the fuel mixture changes, which is constantly.  This enables the vehicles computer to keep a balanced fuel mixture.  When the O² sensor is working correctly your vehicle is running efficiently on fuel and will have low emissions. The aging of an O² sensor means that it reacts slower to the changes that happen in the fuel mixture.  This lag time makes the sensor less accurate causing an imbalance in the fuel mixture.  Oxygen sensors can be diagnosed a variety of ways, most of which require special equipment.  If an O² sensor problem is suspected, the sensor’s response and voltage output can be monitored with a scan tool.  If the tests confirm the O² sensor is dead or sluggish, replacement is the only repair option.  There is no way to “clean” or “rejuvenate” a bad O² sensor. At Hokitika Automotive we have the appropriate equipment to diagnose oxygen sensor faults.  If you suspect your vehicle is consuming too much fuel or has too much black smoke coming out the rear, bring it in and we’ll hook up our scan tool to diagnose the fault.