Code PO430

[abertawe1970]

The old one reads 9.1 ohms, I'm wondering should i clean and put the old one back?
Yes the other bank is also 9.1

[Mandrake]

Ok must be a different resistance to the one on my car then - probably because it is mounted much closer to the exhaust manifold than mine so doesn't need as much heating.

If you still have the new sensor on the car and the only thing you have for testing is a multimeter I would see if you can arrange to measure the voltage across the sensor output (black wire to meter positive, grey wire to meter negative) while the sensor is still connected and the engine is idling.

Depending on the connector the best approach is usually to "backprobe" the connecter with something thin and sharp like a couple of sewing needles. See the following picture for an example of where you would push them in to get contact, basically you push it down between the wire and the rubber padding around the wire, most of the way to the bottom of the connector:



If you turn the key on but don't start the engine you should measure about 0.45 volts - this comes from the ECU and will confirm that you are actually getting a proper connection to your meter. Then start the engine and let it idle for a few minutes and take note of what happens to the voltage.

A voltage between about 0.1-0.4v means the sensor is indicating lean, 0.6v to 0.8v is indicating rich. If it just stays around 0.45v for several minutes it may be that the sensor is faulty or isn't warming up.

At idle after it warms up it should switch high and low as in my previous post. If we know what voltage you're seeing under different conditions that would certainly provide some clues.