lamba senser after the cat?

Checking the wiring. The heater voltage should be battery voltage @ ignition II and with engine running. There will be a relay for it, not sure where though.

Are you sure that the o2 sensor that replaced it was 100% a heated sensor? I've seen people using 'universal' non heated ones instead, out of cheapness.

i believe it is a heated one as it has four wires from it. i can not remember the colours from it, i will have to see if i can find out where the relay is, and tomoz "weather permitting" i will check the voltage at the connector.

Two wires should have battery voltage with the engine running. The other two wires should show a switching voltage between 0V and 0.7V (it may be a bit higher or lower). With it being the post cat sensor, the time spent showing 0.7V should be less than the pre-cat sensor.

"Moray Cuthill cuthill_at_v21.me.uk>" Two wires should have battery voltage with the engine running.

Not really. A four wire sensor will be 1x battery voltage, 2x earth, and 1x ECU signal. The battery voltage and one of the earth wires will be for the heater, the signal and earth wires for the ECU's reading.

Fair enough, my explanation wasn't that clear, but that's what I meant. Across the two heater wires should show battery voltage (ie one at 0V, the other battery volts). The other two wires should show either 0V or about 0.7V across the two wires.

But the 0V wire for the lambda reading may not be tied to the common vehicle earth. It'll most likely be a ECU earth, and connecting it to the vehicle earth may cause problems.

thanks m8. i was going to check the voltage between the two inside wires, i think = they are grey but one has a line along it .

Fair play, old chap :-)

thanks m8. i was going to check the voltage between the two inside wires, i think they are grey but one has a line along it .

If I get time, I'll check the vauxhall wiring diagrams at work tonight, and let you know what colour the vauxhall wiring should be. It could be that the universal lamdba sensor is wired up wrong, or could even be the wrong type.

thanks m

If a standard Bosch type sensor, White wires are heater Black wire signal Grey wire signal earth

Heater resistance usually between 2 - 6 ohms.

Regards, Graham L