Bank 1 Sensor 1 O2 Sensor

X-Type Lambda Sensor

Jaguar X-Type petrol (all years) Part Number C2S51801

Jaguar XK From A30645 - A48700


Standing facing the Flywheel end of the engine, Bank 1 is located on the right hand side of the engine, there are two sensors one up-stream, on the engine side of the catalytic converter, and one down-stream on the exhaust side of the catalytic converter. Bank 1 Sensor 1 is the Upstream sensor.

Bank 1 sensor 1, measures 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.


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.


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