SEAT Leon 1.4s - 2002 - Emission Warning Light

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Wed 12 May 2010 18:45
SEAT Leon 1.4s - 2002 - Emission Warning Light - 28 Haywards Heath

High emission warning light came on . Replaced cat & reset eng man system. Light went out and then came back on months later. Car still running ok.. Replaced #1 LAMBDA sensor, eng thermostat & temp gauge and reset the eng man system. The light went out & came back on next day. Any ideas oin what else it may be please?

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Sat 15 May 2010 23:08
SEAT Leon 1.4s - 2002 - Emission Warning Light - Big John

Is this the "engine management light" and what code is being logged. This engine can have EGR isssues that can be difficult to track down.

1) Where the oil breather connects to the air filter box there is an internal tube within the air filter housing with a "mushroom" valve at the other end - If you do shortish runs this clogs with oil mayo - clean out with carb cleaner or solvent. (Now part of my service) - Easy job - do this first!!

2) collapsed oil breather rubber pipe

3) Blocked oil breather at the rear of the engine

4) Blockage where the metal pipe running front to rear of engine from EGR valve joins the inlet manifold

5)EGR valve sticking shut - small vacuum pipe operated (if it sticks open car will not run OK - also a common issue)

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Mon 24 May 2010 14:13
SEAT Leon 1.4s - 2002 - Emission Warning Light - 28 Haywards Heath

Thanks for your advise on this.

The dashboard light that is constantly on is the "excessive pollution" light.

The fault code generated was 16804. P0420 catalyst system, bank 1: effeciency below threshold.

Thanks

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Tue 17 May 2011 14:56
SEAT Leon 1.4s - 2002 - Emission Warning Light - Vance

Is this the "engine management light" and what code is being logged. This engine can have EGR isssues that can be difficult to track down.

1) Where the oil breather connects to the air filter box there is an internal tube within the air filter housing with a "mushroom" valve at the other end - If you do shortish runs this clogs with oil mayo - clean out with carb cleaner or solvent. (Now part of my service) - Easy job - do this first!!

2) collapsed oil breather rubber pipe

3) Blocked oil breather at the rear of the engine

4) Blockage where the metal pipe running front to rear of engine from EGR valve joins the inlet manifold

5)EGR valve sticking shut - small vacuum pipe operated (if it sticks open car will not run OK - also a common issue)

Is this the "engine management light" and what code is being logged. This engine can have EGR isssues that can be difficult to track down.

1) Where the oil breather connects to the air filter box there is an internal tube within the air filter housing with a "mushroom" valve at the other end - If you do shortish runs this clogs with oil mayo - clean out with carb cleaner or solvent. (Now part of my service) - Easy job - do this first!!

2) collapsed oil breather rubber pipe

3) Blocked oil breather at the rear of the engine

4) Blockage where the metal pipe running front to rear of engine from EGR valve joins the inlet manifold

5)EGR valve sticking shut - small vacuum pipe operated (if it sticks open car will not run OK - also a common issue)

HI Big John,

Had the same problem for months. Tried all of the above - nothing worked. This morning I removed all four fuses pertaining and re-inserted one by one. The last one put in (No.10) lit up the offending light. I then started up and removed that fuse and the engine stopped.

I then re-inserted same and there was a click from the engine compartment as you would expect to hear in a re-set. Started up - problem solved. Light now goes out.

Hopefully you can spread the word.

Regards,

Vance

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Thu 29 Sep 2011 19:17
SEAT Leon 1.4s - 2002 - Emission Warning Light - PaulRath

Hi Vance,

Just wanted to say thanks. Just bought a 2001 Leon and had the warning light come on. Was going to get the car serviced anyway so booked it in and pointed out the warning light. They said they couldn't find anything wrong. And they had cleaned out all the pipes and other stuff that was mentioned above. So they said just to ignore it. Anyhow it was really starting to annoy me so decided to look on here and found your thread. Just tried it and it worked, no more light!!

Hopefully it stays out now until there is a problem that needs fixing. But thanks for the help and saving me a lot of annoyance!

Regards

Paul

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Thu 29 Sep 2011 23:01
SEAT Leon 1.4s - 2002 - Emission Warning Light - Big John

Hi,

The light can also be usually reset by disconnecting the battery for 15 minutes.

If you have already fixed the fault by clearing out breather& pipes/air filter breather pipe- EGR pipes, throttle body and actual valve followed by resetting the light – job done…

On my Octavia the stuck shut EGR “insufficient flow” error takes a few weeks to put the light back on after resetting the light. The EGR nuts/studs look really rusty now so daren’t touch them in case they shear off – car performs really well though.

I now clear out the breather pipe within the air filter as it now seems to block quickly now the car does low mileage(3k) - never had an issue when it did a high mileage (18k). If you don't the oil consumtion goes through the roof (blows oil past the valve seals).

Will have to reset just before next MOT in 2012 as it will fail then with an illuminated warning light.

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Mon 21 Nov 2011 09:53
SEAT Leon 1.4s - 2002 - Emission Warning Light - Vance

Hi Paul,

Just wondering if your light ever came on again. Mine did - most frustrating. Took it for testing on an INNOVA 2000 machine and result came up EGR valve.

Back to the drawing board and will follow previous recommendations re cleaning out and if this doesn't work then I'll replace the valve.

Trust your's is still OK.

Regards,

Vance

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Wed 4 Mar 2015 15:56
SEAT Leon 1.4s - 2002 - Emission Warning Light - JBED

Blocked oil breather pipe full of gunge cleaned it out all well now no more emissions light on .thanks for the tip

Jbed

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Thu 5 Mar 2015 22:29
SEAT Leon 1.4s - 2002 - Emission Warning Light - Big John

Hi,

Thanks for the reminder. I do this every year - usually about march.

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Fri 6 Mar 2015 21:54
SEAT Leon 1.4s - 2002 - Emission Warning Light - Railroad.
P0420 - Catalyst Efficiency Below Threshold is set when the pre and post catalyst O2 sensor readings are too similar, indicating that the catalyst isn't working. Try a bottle of Cataclean in the fuel tank and follow the instructions. If that doesn't cure it you'll almost certainly need to replace the catalyst. You should also replace the pre catalyst O2 sensor.
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