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Old 01-29-2015, 04:44 PM   #1
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Trying to wrap my head around fault code P0430 and P0420

My CEL came on bought Durametric Enthusiast Kit to read the codes. Here is what I got.

P0430
Porsche Fault Code 45 cat conv. efficiency bank 2

P0420
Porsche Fault Code 45 cat conv. efficiency bank 1

So I've been Googling these codes and the clear answer is eluding me to fix this.

I've read 02 sensors bad, cats bad and Valve lift fault (not sure what that means)? Read where these parts were replaced and the same code came back.

Now in combination with those I have this fault code also.

P0327
Porsche fault code 210 knock sensor 1

That's not hard to figure out, but could it be causing the other codes too?
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Old 01-29-2015, 06:11 PM   #2
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Cheap gas (less than 91 octane) or fuel with ethenol have cause the exact same error codes in mine. Best of luck to you!
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Old 01-29-2015, 06:46 PM   #3
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I've got the knock sensor ordered since I know 1 of them is bad. I went ahead and bought 2 so they would be matching units.

The highest octane gas in my area is 91. I've been told the higher octane gas is based to sea level position in your area.

But I'll clear the codes, put some injector cleaner with octane boost added to it and see what happens.

Last edited by KRAM36; 01-30-2015 at 04:42 AM.
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Old 01-29-2015, 08:24 PM   #4
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Sounds like something is fouling your cats. Expensive fix if they get fully loaded up. Yr, model, mileage, any recent work done, sooting tailpipe, burning oil?
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Old 01-29-2015, 08:28 PM   #5
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Do a graph of the pre cat and post cat voltages. If the cats are good, you should gbet an appriximation of a sine wave on the pre cats and close to a straight line on the post cats. If you have a major variation, then the cats are probably bad.
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Old 01-30-2015, 02:39 AM   #6
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I'd put money on the MAF sensor. This summer I got the P0430 code, took it to the Porsche dealer since it was real close when I lved in Germany. They cleared it and said no big deal unless it comes back. 2 days later, P0420. Cleared it. 2 days later, P0430. It did this 5-6 times. I went back to the dealer requesting my O2 sensors changed. They said I would be wasting money and told me to get a new MAF sensor. Ordered it from Rock Auto since it was cheaper. Never got the code since.
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Old 01-30-2015, 03:56 AM   #7
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Sounds like something is fouling your cats. Expensive fix if they get fully loaded up. Yr, model, mileage, any recent work done, sooting tailpipe, burning oil?
2003 S 115k miles. No recent work done. Normal sooting on the tailpipe, no oil burning. I'm actually about 2k miles past when I should have changed the oil and the dip stick is still within normal range. I'm changing the oil today.

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Do a graph of the pre cat and post cat voltages. If the cats are good, you should gbet an appriximation of a sine wave on the pre cats and close to a straight line on the post cats. If you have a major variation, then the cats are probably bad.
I need to get more familiar with the Durametric, just got it a few days ago. I was reading about this.

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I'd put money on the MAF sensor. This summer I got the P0430 code, took it to the Porsche dealer since it was real close when I lved in Germany. They cleared it and said no big deal unless it comes back. 2 days later, P0420. Cleared it. 2 days later, P0430. It did this 5-6 times. I went back to the dealer requesting my O2 sensors changed. They said I would be wasting money and told me to get a new MAF sensor. Ordered it from Rock Auto since it was cheaper. Never got the code since.
Oh, yes this was another fix I read about. I'll clean it today. I forgot about that one.
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Old 01-30-2015, 05:39 AM   #8
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Oh, yes this was another fix I read about. I'll clean it today. I forgot about that one.
I believe I have read on here that it can only be cleaned so many times. When I first got my porsche 4 years ago, it had a rough, jumpy idle along with a code related to the MAF. I cleaned it along with the TB, which fixed it up until this summer when I was getting the codes. I tried cleaning it again, was a no-go this time.
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Old 01-30-2015, 06:24 AM   #9
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I get those codes every once in a while, and when I monitor the durametric I do not have a flat line on the post cat O2 sensors, it is wavy and trails behind the wavy line on the precat O2 sensors. Mine are definitely near the end of their life (2000S 115k miles). But, I don't get the CEL and those codes unless something else is also going on. I figure mine are wearing out, and right near the end of their life, but they are still within spec as long as everything is right. On my passenger side I was getting that code, in conjunction with 2 or 3 other codes (I can't remember what they were, maybe 1128/1130) but one of them was an aging post cat O2 sensor, and also the heater for that sensor had failed. Replacing that sensor cleared up that problem, but I also did some other work at that same time, tightened all clamps in the engine compartment and did spark plugs/orings). That code hasn't come back on that side. (The front O2 passenger sensor is relatively new)

Last year I got the driver side cat code on the way to an autocross. Cleared it and it stayed gone for a while, then came back one or two more times, and then it came back along with a code on the front driver side O2 sensor (aging or heater code, can't remember). Replaced that, and that code hasn't come back.

Interestingly I never get these codes when I am at the track, it is always puttering around town...

I know my cats are at end of life, and I have a set of takeoffs I got that have only 20k on them (or maybe 40k), but I am going to squeeze every bit of life out of the ones I have

Very short version: Fix/resolve all other codes/issues first and see if the 420/430 resolve themselves. Sometimes it does and you can squeak a little bit more life out of them.

Also on Boxster register there was a guy that had a lot of trouble with those codes and it turned out his Alternator was failing and the sensors and computer didn't have enough juice to properly run so he was getting those codes. New alternator solved it for him.
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Old 01-30-2015, 06:25 AM   #10
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I believe I have read on here that it can only be cleaned so many times. When I first got my porsche 4 years ago, it had a rough, jumpy idle along with a code related to the MAF. I cleaned it along with the TB, which fixed it up until this summer when I was getting the codes. I tried cleaning it again, was a no-go this time.
I'll give the MAF sensor cleaning one go. I just picked up some CRC MAF sensor specific cleaner. Also got some CRC complete fuel system cleaner.

Going to change my oil, clean the MAF sensor and take a long drive.

Hope the only code it throws will be for the knock sensor. If the P0430 and P0420 come back, I'll wait for the new knock sensors to get here, install those, clear the codes and take her for another long drive.
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Old 01-30-2015, 06:34 AM   #11
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Originally Posted by steved0x View Post
I get those codes every once in a while, and when I monitor the durametric I do not have a flat line on the post cat O2 sensors, it is wavy and trails behind the wavy line on the precat O2 sensors. Mine are definitely near the end of their life (2000S 115k miles). But, I don't get the CEL and those codes unless something else is also going on. I figure mine are wearing out, and right near the end of their life, but they are still within spec as long as everything is right. On my passenger side I was getting that code, in conjunction with 2 or 3 other codes (I can't remember what they were, maybe 1128/1130) but one of them was an aging post cat O2 sensor, and also the heater for that sensor had failed. Replacing that sensor cleared up that problem, but I also did some other work at that same time, tightened all clamps in the engine compartment and did spark plugs/orings). That code hasn't come back on that side. (The front O2 passenger sensor is relatively new)

Last year I got the driver side cat code on the way to an autocross. Cleared it and it stayed gone for a while, then came back one or two more times, and then it came back along with a code on the front driver side O2 sensor (aging or heater code, can't remember). Replaced that, and that code hasn't come back.

Interestingly I never get these codes when I am at the track, it is always puttering around town...

I know my cats are at end of life, and I have a set of takeoffs I got that have only 20k on them (or maybe 40k), but I am going to squeeze every bit of life out of the ones I have

Very short version: Fix/resolve all other codes/issues first and see if the 420/430 resolve themselves. Sometimes it does and you can squeak a little bit more life out of them.

Also on Boxster register there was a guy that had a lot of trouble with those codes and it turned out his Alternator was failing and the sensors and computer didn't have enough juice to properly run so he was getting those codes. New alternator solved it for him.

Crazy isn't it. So many things can trigger those fault codes. Can't tell you how many threads I've read where people replaced all the O2 sensors or the cats and the codes still came back. I believe all of those where when both fault codes appeared at the same time.
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Old 01-30-2015, 09:57 AM   #12
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I tell you the Porsche computer onboard our cars is a BIG FAT LIAR.

I got a MAF malfunction code when one of the oxygen sensors was fouled. Replaced all four sensors and the MAF was reading fine and voila! I get a lot more power and it purs like a kitten at idle.
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Old 01-30-2015, 11:03 AM   #13
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How many miles do you have to log for the CEL to come back on?

I just put 57 steady cruising miles (no wot) from 45 to 74 mph on the car and no CEL yet.
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Old 01-30-2015, 12:07 PM   #14
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Originally Posted by KRAM36 View Post
How many miles do you have to log for the CEL to come back on?

I just put 57 steady cruising miles (no wot) from 45 to 74 mph on the car and no CEL yet.
Maybe a few drive cycles. As I understand it, the best way to clean out partially fouled cats is to take a spirited drive and get them nice and hot. This oxidizes contaminates and improves cat efficiency.
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Old 01-30-2015, 12:29 PM   #15
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Ok, heading back out onto the road.
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Old 01-30-2015, 12:30 PM   #16
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How many miles do you have to log for the CEL to come back on?

I just put 57 steady cruising miles (no wot) from 45 to 74 mph on the car and no CEL yet.
This link will give you the basics of a drive cycle. You need at least one cold start in the middle - so it can't be done in just a single drive.

How to Perform a Basic Drive Cycle
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Old 01-30-2015, 01:40 PM   #17
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Ok, hit the highway for a bit, then some of my favorite twisties to get her really warmed up, then went back out onto the highway.

Right at 100 miles driven the CEL came back on, but this time without the P0420 fault code.

So now I have

P0327
Porsche fault code 210 knock sensor 1

P0430
Porsche Fault Code 45 cat conv. efficiency bank 2

Will wait for the new knock sensors to come in, but the car goes in the body shop Monday, so it will be a bit to see if the knock sensor could be part of the P0430 fault code issue.

Last edited by KRAM36; 01-30-2015 at 01:45 PM.
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Old 01-30-2015, 02:41 PM   #18
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I tell you the Porsche computer onboard our cars is a BIG FAT LIAR.

I got a MAF malfunction code when one of the oxygen sensors was fouled. Replaced all four sensors and the MAF was reading fine and voila! I get a lot more power and it purs like a kitten at idle.
The bad mixture that fouled the sensor was thanks to the MAF.

It all starts at the MAF.
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Old 02-09-2015, 05:08 PM   #19
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Got my car back from the body shop today. I had cleared the codes before I took it in. The CEL was on and my gas tank was on empty, so somebody was joy ridding my car.

Anyways, hooked up the Durametric to check the fault codes and the knock sensor code was not there, but fault codes P0430 and P0420 were back.

I ordered in 2 new knock sensors lol.

I'm still going to replace them along with spark plugs tomorrow.
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