Technical Lambda sensor closed loop only when manually grounded

[sandaru]

Hi my Punto speedgear 2000 is fitted with new cat and new lambda but it does not go closed loop normally and stuck around 0.475 volts with open loop. But when I manually grounded the ground wire from wiring loom it goes closed loop and can see mostly the fluctuations above 0.450 volts. Please advise.

 

[kido resuri]

Check the ground cables, to the ECU, between battery negative and gearbox, chasis.

 

[sandaru]

Those connections are there and they are very clean with no dirt

 

[kido resuri]

Try to measure the wires from the ECU to the lambda-sensor. Whites are the heater, you should measure 12V voltage between the two, the grey should be ground and the black is the ECU input.

 

[sandaru]

Is it ok to manually ground the ground wire to keep the sensor closed loop when engine running?