Jaguar X Type

The Jaguar X Type is fitted with 4 O2 sensors one up-stream and one down-stream on each of Bank 1 and Bank 2 in line with OBDII requirements. The up-stream sensors are located on the engine side of the catalytic converter, these are the main sensors for control of the fuel air mixture. The downstream sensors located on the exit (non engine) side of the catalytic converter performs the diagnostics for the OBD system.

Bank 1 sensor 1 and Bank 2 sensor 1, measure the oxygen content of the exhaust gasses as they enter the catalytic converter, the level of oxygen in the gas mixture is directly related to the 'burn' efficiency of the engine, it is converted to an electrical signal and fed back to the Engine Control Unit (ECU) to alter the fuel air mixture supplied to the engine.
Bank 1 sensor 2 and Bank 2 sensor 2, measure the residue oxygen content of the exhaust gasses as they exit the catalytic converter, this is used by the ECU to diagnose the overall effency of the combustion process and as part of the OBDII system it's measurement signal will be used to help identify combustion problems within the system.
The ratio of fuel to air in the combustion chamber is identified with the Greek letter 'lambda' hence the term 'lambda sensor' as the name given to the O2 sensors used in vehicles. Ideal combustion of gasoline occurs when the fuel : air ratio is 14.7:1 (fuel is 6.8% of the mass of the mixture) at this point the lambda value of 1.0 is assumed. As the lambda value drops the fuel:air mixture is becoming richer (less air more fuel) and conversely as the value rises the mixture is becoming weaker (more air to fuel).

With the engine up-to normal working temperature, check the output of the sensor wire, normally black with Zirconia sensors, you should expect an output of 0.2 – 0.8 volts fluctuating between these reading approximately 2 – 3 times per second. If the output voltage is lower than this, i.e. 0 – 0.2 volts there will be a lean running or excess oxygen problem. If the voltage is higher than this, i.e. 0.8 – 1.2 volts then there will be a rich running or excess fuel fault.