Suzuki sx4 CEL confusion

A friend of my mine has an '07 SX4 with a seemingly odd problem. It's a well kept low mileage old man's car.

It has a P0420 fault code, and smells like it's running rich.

Using the Torque app, it appears that the upstream O2 sensor is not producing any signal, it stays at 0v even when the sensor is disconnected, and never gives a fault code for the O2 sensor. As far as I can tell this car doesn't have separate fuses for the sensors, and all fuses and relays are good.

I'm confused because I've never seen a dead sensor not give a fault code, nor have I seen a disconnected sensor not give a fault in seconds, this one was started and stopped several times over 5 minutes and didn't fault code.

Am I over thinking a dead sensor, or is there something more going on with this?

That O2 sensor is darned expensive and readily available.

Bump

Anybody???

Have you checked any specific Suzuki websites for that code? Sorry I'm no help otherwise.

http://www.obd-codes.com/p0420

Is it going into closed loop mode?

BrokenYugo wrote: Is it going into closed loop mode?

I'm pretty sure it is. If he hasn't had it fixed already I'll recheck this weekend.

Update: I spoke to my friend this evening, he said that since I cleared the code, it's run perfectly and the CEL hasn't come back. Curious. When I was checking it out last week it was running so rich my eyes were watering.

I wonder if the ECU had a glitch that clearing the code solved?

Running rich will cause that code. Every time I go WOT for very long on my Focus I get that code.

Reason is that because the car is supercharged I have tuned it to have an AFR of ~10:1 on the top end. If I keep it up there very long it overwhelms the catalytic converter by being so rich. Just reset and it is fine until the next time I get silly.

If it does it again you need to find out why it is running so rich.