Originally posted by Bakeoff
If it's a D series, the secondary O2 goes on the cat itself, not on the manifold. So you'd have one where they all go on obd1 cars (on the upper half of the manifold), and another on the cat.
Hrm, right now it's running with an obd2 sensor setup on an obd1 ecu. With one 02 sensor immediately beofre cat, and one immediately after.
If the obd1 02 sensor location is higher up on the manifold, I believe that makes it a 1-wire 02 sensor, i.e. an 02 sensor without a heating element. Hence the placment near the manifold to heat it up.
So I guess I need to: tap an 02 bung in the a-pipe/collector, and then make sure I am using an ecu that can control the heated sensor. I am using a p28 currently.
-PHiZ