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Engine Light


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I have a recoring problem, the engine light comes on with code P0431 and P0421 which is somit to do with the cat

My car is an 07/56 3.4 Boxster S with 37000 miles

I believe the codes are to do with the cat but have had the car at a local mot station who confirm the cats are doing their job.

Any suggestions?

Edited by petrolhead
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  • Admin

P0421 Catalytic conversion

P0431 Catalytic conversion

NOTE: The catalytic converter monitor compares the amplitude of the oxygen sensor behind the catalytic converter with the amplitude of a computed limit catalytic converter during defined air gulping and enrichment phases. The amplitudes allow conclusions to be drawn about the ability of the catalytic converter to store oxygen.

Possible fault causes

- Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)

- Valve lift error

- Aged oxygen sensor behind catalytic converter

- Catalytic converter faulty (pre-catalytic conversion rate too low)

If an aged oxygen sensor (oxygen sensor signal behind catalytic converter, dynamism) is detected together with this fault:

- remedy the fault "Oxygen sensor signal behind catalytic converter, dynamism" first,

- Then check if this fault - catalytic conversion - has been entered again.

IMPORTANT: If the primary catalytic converter is faulty, check the main catalytic converter for damage and also replace it if necessary.

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  • 2 weeks later...

P0421 Catalytic conversion

P0431 Catalytic conversion

NOTE: The catalytic converter monitor compares the amplitude of the oxygen sensor behind the catalytic converter with the amplitude of a computed limit catalytic converter during defined air gulping and enrichment phases. The amplitudes allow conclusions to be drawn about the ability of the catalytic converter to store oxygen.

Possible fault causes

- Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)

- Valve lift error

- Aged oxygen sensor behind catalytic converter

- Catalytic converter faulty (pre-catalytic conversion rate too low)

If an aged oxygen sensor (oxygen sensor signal behind catalytic converter, dynamism) is detected together with this fault:

- remedy the fault "Oxygen sensor signal behind catalytic converter, dynamism" first,

- Then check if this fault - catalytic conversion - has been entered again.

IMPORTANT: If the primary catalytic converter is faulty, check the main catalytic converter for damage and also replace it if necessary.

Hi Loren,

I've got an '06 Cayman S that's thrown the P0421 code for the second time. My mechanic friend just cleared it the first time, and now I'm wondering what to do. I've owned the car for six months, first issue with it. I've searched the forums here and seen a couple of your responses on this issue. Can you confirm that the P0421 code (i.e., NOT the P0431 code) means possible fault causes:

- Catalytic converter faulty (pre-catalytic conversion rate too low)

- Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)

Also, can you offer me some guidance about whether I should have my mechanic start with investigating/replacing the oxygen sensors (I tend to doubt their position is swapped or this issue would have been occurring before, right?) or just go ahead & replace the catalytic converter (since it seems that this is a known issue with the MY06 Cayman S)? Ideally the work would be under warranty as I'm good through Oct '10 thru Porsche plus I bought an extended warranty :).

Cheers,

Liz

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P0421 Catalytic conversion

P0431 Catalytic conversion

NOTE: The catalytic converter monitor compares the amplitude of the oxygen sensor behind the catalytic converter with the amplitude of a computed limit catalytic converter during defined air gulping and enrichment phases. The amplitudes allow conclusions to be drawn about the ability of the catalytic converter to store oxygen.

Possible fault causes

- Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)

- Valve lift error

- Aged oxygen sensor behind catalytic converter

- Catalytic converter faulty (pre-catalytic conversion rate too low)

If an aged oxygen sensor (oxygen sensor signal behind catalytic converter, dynamism) is detected together with this fault:

- remedy the fault "Oxygen sensor signal behind catalytic converter, dynamism" first,

- Then check if this fault - catalytic conversion - has been entered again.

IMPORTANT: If the primary catalytic converter is faulty, check the main catalytic converter for damage and also replace it if necessary.

Hi Loren,

I've got an '06 Cayman S that's thrown the P0421 code for the second time. My mechanic friend just cleared it the first time, and now I'm wondering what to do. I've owned the car for six months, first issue with it. I've searched the forums here and seen a couple of your responses on this issue. Can you confirm that the P0421 code (i.e., NOT the P0431 code) means possible fault causes:

- Catalytic converter faulty (pre-catalytic conversion rate too low)

- Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)

Also, can you offer me some guidance about whether I should have my mechanic start with investigating/replacing the oxygen sensors (I tend to doubt their position is swapped or this issue would have been occurring before, right?) or just go ahead & replace the catalytic converter (since it seems that this is a known issue with the MY06 Cayman S)? Ideally the work would be under warranty as I'm good through Oct '10 thru Porsche plus I bought an extended warranty :).

Cheers,

Liz

Erasing the fault does not fix anything.

There are tests that can be preformed to see if the cat is functioning as it should be. He should run those tests. If the cat passes then replace the sensor.

  • Upvote 1
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  • 2 months later...

Hi, I'm new here but have already experienced a similar problem.

Guildford OPC cancelled the code, did tests but the fault would not repeat itself.

I bought a fault reader and by the time I got home the fault has popped up again, the following day the engine light lit up.

The car was then returned to the OPC I bought the car from two weeks previously.

They found one cat failed, the other showing signs of failure and both were replaced under warranty after some discussions with Porsche.

Porsche didn't like the fault not showing up in the 111 point check and pre-sale check but did mention there is possibly a fault with a batch of 2007 cats as they have had a few failures. My car has covered 22k miles.

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