Please help me diagnose SES problem

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Mar 19, 2004 | 11:53 PM

Bigvic

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From: Waco, TX

Please help me diagnose SES problem

Alright first off, the engine is not an LS1, but it is LS1 based. It is the 4.8 in my wife's 02 Tahoe. She has approx. 50K on the engine, and now we have a SES code. Two to be exact. Sometimes the light will stay on for a few days then might go off for a week or two. I had autozone pull the codes and although I don't remember the exact code numbers, I do remember the descriptions. In a nutshell it said that both the right and left banks of the engine were not running efficiently (one code for each side).

Now my thoughts on the situation are maybe bad cats or O2's, but what are the chances that either one of those would go out on both sides of the engine at the same time? So then I think maybe it could be the maf? I did put a K&N filter in it a while back, maybe I over oiled it and got oil on the maf element, but the filter doesn't look over oiled.

When we bought it we did get the extended warranty, but each visit now costs us $100 since the expiration of the original warranty, so I would like to be able to fix the problem myself for under a $100 if it is possible. Now I know that just by reading my post it will be difficult to diagnose this problem, but if you guys could give me some ideas on what to check out that may be the problem, I would really appreciate it.

Also, when the SES is on, the engine runs the same, however I don't know if gas consumption has changed or not.

Mar 20, 2004 | 01:02 AM

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From: San Diego

Do you have any idea if it is the Cats? Perhaps it is spark plugs. If you could post the codes, that would be really helpfull.

If you can, I would start with spark plugs, check their condition/gap, if that checks out, see if your MAF is dirty/coated in junk. That should be giving you an incorrect voltage code however.

When the MIL (SES Light) is lighted, and you listen to the engine, do you hear any tapping, or clicking that might indicate a misfire condition?
Hope that helps.
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LS1 Powered Porsche 911 (in the making)

Mar 20, 2004 | 02:04 PM

Bigvic

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From: Waco, TX

Well I changed the plugs last weekend, but that didn't change things. At least that didn't remove the code. If the plugs were the culprit, would I have to remove the code or would it do it on its own?

I will check out the maf when she gets home later tonight.

As far as the cats are concerned, how would I know if they were bad?

Mar 20, 2004 | 09:05 PM

blk~2000~Z28

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From: Marysville, OH

Was it any of these? There are other codes like "insufficient" could it have been one of those?

P0430 - Catalyst System Low Efficiency Bank 2
P0431 - Warm Up Catalyst Efficiency Below Threshold (Bank 2)
P0432 - Main TWC Efficiency Bank 2 Below Threshold
P0433 - Heated TWC Efficiency Bank 2 Below Threshold
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P0421 - Warm Up Catalyst Efficiency Below Threshold (Bank 1)
P0422 - Main TWC Efficiency Bank 1 Below Threshold
P0423 - Heated TWC Efficiency Bank 1 Below Threshold
P0424 - Heated TWC Temperature Bank 1 Below Threshold

Mar 28, 2004 | 04:55 PM

Bigvic

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From: Waco, TX

Okay, I went and had the codes scannned today. The guy said that it was a PO430. He said that that code showed up twice. Right off the bat he said it was my O2s, but I wanted to check with you guys first.

Thanks,
Victor