Contour Enthusiasts Group Archives Forums General Troubleshooting CEL P0420 - What are my options?

Actually, now that I think of it, I've been getting a Bank 2 code (I hope, otherwise I just screwed myself). I'll be sure to set the code after this weekend, so I'll know for sure. I'll nominate myself for Bonehead of the Year if I did this wrong.

Isn't Bank 1 the firewall side? If so, more reason to make the dealer do it.

I'm leaving the precat in the manfold I bought. I got it off a 32,000 mile wrecked 98, so that precat should have plenty of life left. Who wants to bet I get a code for the other side right after I replace this one?

I didn't see much point in gutting one precat. It would throw the A/F ratio off on the banks (gutted vs. not), and since I can only monitor one side at a time (with S-AFC or wideband O2), there would be no way to get the settings right. Either one side would end up rich or the other would end up lean.

Originally posted by PA 3L SVT:

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Isn't Bank 1 the firewall side?

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Yes.

I'm pretty sure bank 1 is closest to firewall/driver. Gutting 1 precat is probably not a good option.

Well guys, thanks for all the info. Sounds like I'll be putting the stock intake and Y pipe back on. Then it's off to see the dealer. I'll double check with them that it is covered prior to putting anything back. The only thing I can't put back is the stock resonator which I got rid of a while back (not inculding wheels, springs, and sway bar which I can't imagine them balking at in regards to this). Currently, I have a Magnaflow in. Hope they don't give me grief about that.

Thanks,
Jay

FWIW, my P0420 (no other codes present) was due to a failing downstream O2 sensor, so I second (third?) the notion of replacing that sensor first. This one is waaaaaaay easier than the bank 1 upstream sensor!

Ok, it's just now registering in my thick head that you guys are saying downstream O2 sensor. I kept assuming it was an upstream one. Or maybe I'm just not understanding the terminology.

So how many sensors are there? Where are they? And which one it is that possibly needs to be replaced in this situation?

I've only actually seen one myself and it's the one on the Y pipe just before the main cat. So I was assuming the one we were talking about must be on the manifold (upstream) since the code is specifying a particular Bank.

Sensor overloaded,
Jay

Originally posted by SVT-N:

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So how many sensors are there?

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I believe that you should have four O2 sensors. Two on each bank (and there are two banks).

Originally posted by SVT-N:

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Where are they?

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Bank 1 is next to the firewall (since the engine is put in sideways), and Bank 2 is next to the radiator. Each bank has two sensors, one upstream and one downstream. The upstream sensors are hardest to get to (with Bank 1 being the hardest of all).

The Bank 1 upstream sensor is underneath the ignition coil(about 9-12") . You can't really see it unless you get under the car or remove the ignition coil.

The Bank 2 upstream sensor is next to the oil filter. You should be able to see it from above.

I believe that you should be able to see both of the downstream sensors by looking underneath the car.

Originally posted by SVT-N:

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Ok, it's just now registering in my thick head that you guys are saying downstream O2 sensor. I kept assuming it was an upstream one. Or maybe I'm just not understanding the terminology.

So how many sensors are there? Where are they? And which one it is that possibly needs to be replaced in this situation?

I've only actually seen one myself and it's the one on the Y pipe just before the main cat. So I was assuming the one we were talking about must be on the manifold (upstream) since the code is specifying a particular Bank.

Sensor overloaded,
Jay

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P0420 would be triggered most likely by a downstream sensor after the precat. So, I would look at the bank 1 downstream sensor. These are very easy to change. These sensors monitor the exhaust after going through the precats.

Ok, what you guys are saying makes sense. The only question I have is... then what sensor is it that is on the Y pipe just before the main cat?

Originally posted by SVT-N:

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Ok, what you guys are saying makes sense. The only question I have is... then what sensor is it that is on the Y pipe just before the main cat?

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Downstream, Bank 1.