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2000 Infiniti I30 Cat Converter? Dead or a Bad O2 Sensor?

The “Service Engine” light is on and the stored code is P0430. 144,000 miles and the front tube and sensors were replaced in a recall three years ago. Before I surrender to the gentle and expensive ministrations of the Infiniti dealer, here is my question: How likely is it that the O2 sensor and not the converter is bad? A new sensor is about $200 and an aftermarket converter is about $300, but neither one is returnable if I replace it myself and guess wrong. Any insights?

An exhaust leak or a bad O2 sensor will trigger this code.

Look for an exhaust leak and measure the output from the O2 sensor. You’ll need a service manual to give you the specs.

Why would you want to go to the Infinity dealer? Any decent mechanic should be able to diagnose and repair this.

Actually, I wouldn’t go to the dealer. There’s an excellent mechanic nearby. No exhaust leak – checked thoroughly. The electical test requires a dual-input voltmeter, where you count the switching rate of each sensor simultaneously at 2,000 RPM and then calculate the ratio to see if it’s within limits.

I may be whistling past the graveyard here – but I just spent $1,400 having my other car fixed and it would be nice if I could do the repair myself.

Well, if you can quote the specs, you should be able to do it yourself. Do you have a dual-input voltmeter? Do you have an O2 sensor socket?

If not, this is a perfect opportunity to add to your tool collection.

At 144k miles, there is an excellent possibility that the other O2 sensors are getting too slow to satisfy your OBD II control system.

I would not trust the verdict of a voltmeter, even a dual input voltmeter, when it comes to identifying an aging O2 sensor. You really need an oscilloscope to see if it is still up to par.

A new OEM oxygen sensor for this car is $110 on line with free shipping from any of several reputable sources. If you take it to a shop, whatever the problem turns out to be, you are almost certainly going to end up with a new sensor, so you really have nothing to loose trying it yourself.

That’s my thinking as well, especially since the trouble code is intermittent. If I clear the code, sometimes the car will go weeks before it resets, and other times it’s just a few hours. So I’m going to start with the sensor and if that fails, an after-market front cat converter is about $250. Thanks for your advice