Diagnostic code P0420 (help)

eskezz · 8th December 2008, 14:25

Had my 75 1.8t saloon (03/53) for 2 months now. The engine management light appeared after the 1st week of ownership with diagnostic code P0420 (relating to cat conv). A new cat was fitted back in 08/08 by the prev owner to overcome MOT fail and I have done 1200 miles since fitting with total miles now at 13400.
Been to and fro to my own mechanic who has done a full emissions test (as per MOT) and all readings (CO/HC/Lambda) are well within limits. Have had the light appear 4 times in all-take it back-new diagnostic check reveals same error code-reset and then light reappears a week or so later. Car runs fine-no misfires or cutting out. Spoke to the garage that fitted the replacement cat and they are happy to have another look. However before doing the 200 mile round trip has anyone got any ideas as to the root cause or the way forward. (the diagnostics used would I presume not be a T4). Thanks

Eric

CDTi · 8th December 2008, 14:30

Here is a generic description:

http://www.obd-codes.com/p0420

Evansabove · 8th December 2008, 14:47

A colleague of mine has a Toyota Camry and if he puts "Supermarket Petrol" in then he gets an engine warning light. If he puts Shell in the light goes out and stays out. I guess it is worth a try to see if this is your problem. The Toyota forums say it is to do with the Catalytic converter etc. Of course "other" major fuel brands are available.
When I asked my garage whether I needed a new fuel filter fitted at my last service (diesel) he asked where I get my fuel from and when I said "Shell" he said I would not need the filter but if I had "Supermarket" then he would definately change it. Obviously ther IS a difference between fuel suppliers.

T-Cut · 8th December 2008, 14:53

Maybe it needs a new lambda sensor? I had a new catalyst fitted and started getting the same fault code every now and then. I'll be fitting a new sensor when I can under the car. I wonder if they tend to get damaged during cat refits?

TC

Chilljohn · 8th December 2008, 15:30

had this with my 190 , if its a cheap cat youll no end of problems , remeber the car has to complete a drive cycle to test the emmisions (about 40 miles depending how you drive and on hte 1st error will only ping up a pending error and no mil light )

after changing all 3 sensors on mine and still getting the error the cat was changed another 2 times but still got the error, however putting a steel monolith cat on the problem went away

eskezz · 9th December 2008, 18:09

Thanks for the info all. Looks like a trip back to the original garage to see what type of cat (ceramic or steel) was fitted and take it from there. Either that or a piece of black masking tape to hide the light when it next appears.
Anyone fitted a steel cat and where from and at what price?
They seem to be around 3 times more expensive.

SKS Disco · 10th December 2008, 08:17

Quote:

Originally Posted by eskezz

Had my 75 1.8t saloon (03/53) for 2 months now. The engine management light appeared after the 1st week of ownership with diagnostic code P0420 (relating to cat conv). A new cat was fitted back in 08/08 by the prev owner to overcome MOT fail and I have done 1200 miles since fitting with total miles now at 13400.
Been to and fro to my own mechanic who has done a full emissions test (as per MOT) and all readings (CO/HC/Lambda) are well within limits. Have had the light appear 4 times in all-take it back-new diagnostic check reveals same error code-reset and then light reappears a week or so later. Car runs fine-no misfires or cutting out. Spoke to the garage that fitted the replacement cat and they are happy to have another look. However before doing the 200 mile round trip has anyone got any ideas as to the root cause or the way forward. (the diagnostics used would I presume not be a T4). Thanks

Eric

It is the catyltic converter. Guaranteed.
If garage fitted WAG000660SLP or WAG000661SLP or another aftermarket type, these are known to play up. They are very slightly undersize so overheat by just a couple of degrees. This is enough to turn the MIL light on.

The good news is XPart have now managed to get a supply of the original spec WAG000660 cats.
These have been on exhaustive road tests and cure the problem.

Hope this info helps.

Phil · 10th December 2008, 08:23

Quote:

Originally Posted by Transam

It is the catyltic converter. Guaranteed.
If garage fitted WAG000660SLP or WAG000661SLP or another aftermarket type, these are known to play up. They are very slightly undersize so overheat by just a couple of degrees. This is enough to turn the MIL light on.

The good news is XPart have now managed to get a supply of the original spec WAG000660 cats.
These have been on exhaustive road tests and cure the problem.

Hope this info helps.

What are XPART likely to be doing about this? Presumably exchange foc?

SKS Disco · 10th December 2008, 08:28

Quote:

Originally Posted by Phil

What are XPART likely to be doing about this? Presumably exchange foc?

No idea. Not my dept.

I only do the technical bit.

Phil · 10th December 2008, 08:30

Am I allowed to ring xpart and quote that, or will it get you into trouble?

8th December 2008, 14:25	#1
eskezz Loves to post rover 75 saloon Join Date: Oct 2008 Location: st helens Posts: 261 Thanks: 0 Thanked 1 Time in 1 Post	Diagnostic code P0420 (help) Had my 75 1.8t saloon (03/53) for 2 months now. The engine management light appeared after the 1st week of ownership with diagnostic code P0420 (relating to cat conv). A new cat was fitted back in 08/08 by the prev owner to overcome MOT fail and I have done 1200 miles since fitting with total miles now at 13400. Been to and fro to my own mechanic who has done a full emissions test (as per MOT) and all readings (CO/HC/Lambda) are well within limits. Have had the light appear 4 times in all-take it back-new diagnostic check reveals same error code-reset and then light reappears a week or so later. Car runs fine-no misfires or cutting out. Spoke to the garage that fitted the replacement cat and they are happy to have another look. However before doing the 200 mile round trip has anyone got any ideas as to the root cause or the way forward. (the diagnostics used would I presume not be a T4). Thanks Eric

8th December 2008, 14:30	#2
CDTi This is my second home No longer in the MGR club Join Date: Nov 2006 Location: Tipperary Posts: 3,933 Thanks: 35 Thanked 51 Times in 35 Posts	Here is a generic description: http://www.obd-codes.com/p0420 __________________ 'Tis better to be silent and be thought a fool, than to speak and remove all doubt.

8th December 2008, 15:30	#5
Chilljohn Posted a thing or two MG HS PHEV Join Date: Nov 2006 Location: Worksop Posts: 1,576 Thanks: 58 Thanked 80 Times in 75 Posts	had this with my 190 , if its a cheap cat youll no end of problems , remeber the car has to complete a drive cycle to test the emmisions (about 40 miles depending how you drive and on hte 1st error will only ping up a pending error and no mil light ) after changing all 3 sensors on mine and still getting the error the cat was changed another 2 times but still got the error, however putting a steel monolith cat on the problem went away __________________ John Free enable of digital speedo readout on message centre (takes 2 mins) Free Vis motor testing, via obd port courtesy of my delphi so no need to take anything apart, along with free code scan including abs and airbag message me for details

10th December 2008, 08:30	#10
Phil This is my second home Rover 75 CDT Connoisseur SE Join Date: Nov 2006 Location: Wales Posts: 12,227 Thanks: 469 Thanked 523 Times in 241 Posts	Am I allowed to ring xpart and quote that, or will it get you into trouble? __________________

8th December 2008, 14:47	#3
Evansabove Loves to post Rover 75 CDT Conn SE Join Date: Mar 2008 Location: Bournemouth Posts: 272 Thanks: 1 Thanked 6 Times in 6 Posts	A colleague of mine has a Toyota Camry and if he puts "Supermarket Petrol" in then he gets an engine warning light. If he puts Shell in the light goes out and stays out. I guess it is worth a try to see if this is your problem. The Toyota forums say it is to do with the Catalytic converter etc. Of course "other" major fuel brands are available. When I asked my garage whether I needed a new fuel filter fitted at my last service (diesel) he asked where I get my fuel from and when I said "Shell" he said I would not need the filter but if I had "Supermarket" then he would definately change it. Obviously ther IS a difference between fuel suppliers.

8th December 2008, 14:53	#4
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Maybe it needs a new lambda sensor? I had a new catalyst fitted and started getting the same fault code every now and then. I'll be fitting a new sensor when I can under the car. I wonder if they tend to get damaged during cat refits? TC

9th December 2008, 18:09	#6
eskezz Loves to post rover 75 saloon Join Date: Oct 2008 Location: st helens Posts: 261 Thanks: 0 Thanked 1 Time in 1 Post	Thanks for the info all. Looks like a trip back to the original garage to see what type of cat (ceramic or steel) was fitted and take it from there. Either that or a piece of black masking tape to hide the light when it next appears. Anyone fitted a steel cat and where from and at what price? They seem to be around 3 times more expensive.