Does anyone know if downstream 02 can be tested by installing into upstream O2 wiring harness and looking for the correct switch rate? I know downstream is suppose to have a steady signal ,but im getting a p0420 code and wondering if i could test it on upstream O2 wiring harness?
I suppose you could try? :huh: It'd depend on if the upstream and the downstream connectors are the same style. Sometimes they are, often they're not. You'd also need the sensor pins to be in the same locations so the sensor works correctly. Consult a wiring diagram before attempting this.
Also keep in mind that downstream heaters often consume about half of the current of upstream sensors. That means they usually don't become active quite as quickly. Installing the sensor in the upstream port, closer to the engine, may offset that.
