Hi been told i can do a resistance test on a lamba senser to test if its failed, does anyone know what readings i should be looking for ,ta.

 

you could check the heater element within the sensor, you should see something like 10 ohm. but the sensor itself cannot be checked that way.
the sensor is a voltage source between 0 and 1 volts and it's internal resistance is dependant on temperature of the sensor.