nickm Page 38 there seems to be an overload relay in the circuit cardiagnostics.be/-now/VOLVO%20VIDA%20VADIS_bestanden/VOLVO-%20850%20SystemWiringDiagrams.pdf
captain_anchovy According to the circuit the two white wires from the O2 sensor for the pre heat become a black and a green. I think the green should be 12 v engine running. I measure mine at about 5 v. This would explain why the heating element isnt working. But i cant understand where 5 v is coming from.
nickm Green/Orange for both sensors should see 12volts to ground. This is the preheat voltage wire. Green and Green/Black (front signal) Green white and Black (rear signal)
