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Diagnostics should show a faulty sensor..yes
Here is the info. for the Rovacom GEMS engine diagnostics programme relating to sensor inputs..in particular the Lambdas
Realtime live display of the information the electronic control unit of the selected vehicle system is currently deriving from its input sensors.
FUELLING
Loop status: This confirms the current status of the GEMS loop tuning system and tells if it is currently active and working correctly. Options are:
OPEN NOT YET SATISFIED CONDITIONS: The engine is not running or is still too cold to use the feedback from the sensors so when there is nothing wrong, the system is open loop.
CLOSED USING O2 SENSORS NORMALLY: Proper operation with no faults.
OPEN DUE TO DRIVING CONDITIONS: The system has been using the sensors and there are no problems, but it has decided not to use them at the moment as the feedback is not required for correction.
OPEN DUE TO A DETECTED FAULT: There is a fault with the sensor and the system has reverted to using the pure map without the aid of closed loop correction.
CLOSED BUT AN O2 SENSOR IS FAULTY: This can only happen in vehicles fitted with 2 sensors per bank (NAS). Although the system knows one of the sensors is faulty it can switch to using the other one to give closed loop fuel correction.
Pre cat Oxygen Sensor: This is the returning voltage value from the odd/even banks front (pre-catalyst) Oxygen sensor, which under normal operation (closed loop) should switch between very low values (near zero volts) when the mixture is too rich and very high values (near 5.0 volts) when the mixture is too weak. This switching may pause for brief periods, which is normal. Some markets (mainly Australia) had no sensors fitted and work entirely open loop.
Post cat Oxygen Sensor: This is the returning voltage value from the even banks rear (post-catalyst) Oxygen sensor, which under normal operation (closed loop) should switch between very low values (near zero volts) when the mixture is too rich and very high values (near 5.0 volts) when the mixture is too weak. This switching may pause for brief periods, which is normal. Sensors are only fitted after the catalyst in some countries like North America (NAS) and are used mainly for confirming the correct operation of the catalytic converter although this sensor can be used in the event of failure of the main pre-catalyst sensor.
Fuel trim long term: The percentage of alteration from the map value that the system is applying, to compensate for engine temperature, air temperature, fuel temperature, current engine load and other related conditions.
Fuel trim short term: The percentage of alteration from the map value that the system is applying, to momentarily compensate for feedback information, acceleration and other load conditions.
yep i agree with irish,
