Hi I'm looking to buy a lamda sensor/o2 sensor (exhaust mounted) to work with an air-fuel meter. i've found two types of sensor - one 3-wire and one 4-wire. the 3-wire seems to be "heater, heater, signal" and the 4-wire is "heater, heater, signal, earth" with the 'heater' wired presumably running the pre-heat function to bring the lamda sensor up to operation temperature more quickly Obviously, the signal wire runs to the gauge, and the earth (on the 4-wire) runs to the ground. But on both the 3-wire and 4-wire, where do I run the two heater wires to? Is one ignition-switched 12v? WHat's the other??? I know this is a stupid question, but hope someone can help. Cheers Dan Edited by: ThePatyPlus
