Catalyst error code

Sosban · 21st August 2009, 16:18

Whilst out driving today, the engine management light came on. When I checked the error code it came up P0420, which according to my list means "Catalyst Efficiency Below Threshold (Bank 1)".

I reset the code and drove another 20 miles or so without the warning light coming back on. Does anyone know the significance of this error, and what I need to do to correct it?

Thanks in advance.

T-Cut · 21st August 2009, 18:29

It means the catalyst is not performing to the specifiction set down. The 1.8 turbos are particularly prone to this due to the ceramic matrix coming loose and rattling. It eventually wears away as shown here:

Some of the later OEM catalysts supplied by Xpart also under perform, giving rise to the same fault indication. Changing the lambda sensor is unlikely to make any difference. Soon be time for a replacement I suspect.

TC

Sosban · 21st August 2009, 20:05

Thanks T-Cut, looks like I'll have to start looking for a replacement then!

sworks · 22nd August 2009, 05:44

Do you have a code reader or scan tool? If it reads data you need to check the voltages of both oxygen sensors.
Upstream should move between about 0.2v and 0.8v
downstream should flat line around 0.4-0.5 volts
If the downstream is fluctuating it's the catalyst

Sosban · 22nd August 2009, 08:40

I use a Scangauge II. It doesn't read values from the oxygen sensors by default, and I don't have the knowledge to program the unit to scan these sensors. Thanks for the info.

eskezz · 22nd August 2009, 17:27

My car had a new cat fitted 1 year and 6K miles ago and still gets code 0420 when the EML comes on. I just reset the light and as the car has passed 2 MOT's since fitting I am reasonably happy that all is OK. However I could be wrong. Have an emission test and see what shows up-should indicate the condition of the cat.

Sosban · 23rd August 2009, 10:23

Had my MOT only last month, with no probs. ECU warning light hasn't come on again, so I think I'll wait a while to see what happens.

Greccehus1 · 8th April 2019, 13:05

I recently had some problems with an exhaust valve fixed. Engine runs as smooth as you like, but now the P0420-code spoils the fun. Is it unwise to keep on driving with this problem (just because the valve problem wasn't solved cheaply

)?

slovcan · 8th April 2019, 13:33

Quote:

Originally Posted by Greccehus1

I recently had some problems with an exhaust valve fixed. Engine runs as smooth as you like, but now the P0420-code spoils the fun. Is it unwise to keep on driving with this problem (just because the valve problem wasn't solved cheaply

)?

Hi,

Well, the answers are above - catalytic converter or oxygen sensor. Get the code reset and see if it comes back. Run a tank of good fuel with a bottle of catalytic converter cleaner something like this https://www.amazon.co.uk/Granville-1.../dp/B005OW0WJI . That might prolong the life of the cat and might even help clean the O2 sensors. Bad O2 sensors will cause bad gas mileage and damage the cat, but OK to drive until you get it fixed (don't take a year to do it!).

What engine is it and what's the story on the exhaust valve - burned, for how long?

Cheers,
Glenn

Greccehus1 · 8th April 2019, 16:24

Hi Glenn,

thanks for your quick reply. The burned valve problem started mid January I think (misfire). The check engine light came on and first thing my garage did was replace the coil. This helped for two days or so and then the light came on again. I tried loads of things among which changing the plugs, changing coils again (some people on the Dutch Rover forum told me that Rover 75's can be particular when it comes to brands (Beru only), cleaning the stepper motor and using Wynn's cleaner products for injectors, valves, petrol system and cat. All to no avail. Another garage told me after checking compression that cylinder two had none. They didn't want to open the engine since they had no experience with the 1.8 turbo engine. I found a Rover garage who found out about the valve. 1.5 week later I was loads of Euro's poorer and as mentioned above a smoothly running engine richer. However, this morning I was unpleasantly surprised to see the light coming on again. Checking with TOAF showed the P0420-code AND even more irritating: I now seem toexperience trouble starting it; it takes a moment or two to pick up revs (are these two symptoms related?)
The engine is like I said above a 1.8 turbo.

Cheers,

Jasper

21st August 2009, 16:18	#1
Sosban Regular poster MG ZT 1.8+ Join Date: Feb 2009 Location: Barry, South Wales Posts: 81 Thanks: 0 Thanked 0 Times in 0 Posts	Catalyst error code Whilst out driving today, the engine management light came on. When I checked the error code it came up P0420, which according to my list means "Catalyst Efficiency Below Threshold (Bank 1)". I reset the code and drove another 20 miles or so without the warning light coming back on. Does anyone know the significance of this error, and what I need to do to correct it? Thanks in advance.

22nd August 2009, 05:44	#4
sworks Been absent for a while… Rover 75 Tourer, Classic mini Cooper S, Abarth 595 competizione, MG TF and a Hyundai Tucson PHEV Join Date: Feb 2007 Location: Cumbria Posts: 13,065 Thanks: 1,033 Thanked 1,686 Times in 1,040 Posts	Do you have a code reader or scan tool? If it reads data you need to check the voltages of both oxygen sensors. Upstream should move between about 0.2v and 0.8v downstream should flat line around 0.4-0.5 volts If the downstream is fluctuating it's the catalyst __________________ ................................................. 'Marmite' Possibly one of the most famous 75 tourers produced! left the production line as the last of only Three Rover 75 tourers produced in Trophy Yellow. 48 hours later Longbridge closed. The last sold ordered 75 Tourer. Paid for by the Phoenix Four and handed over by John Towers to the Warwickshire Northampton Air ambulance service as a Rapid Response vehicle

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21st August 2009, 18:29	#2
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,751 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	It means the catalyst is not performing to the specifiction set down. The 1.8 turbos are particularly prone to this due to the ceramic matrix coming loose and rattling. It eventually wears away as shown here: Some of the later OEM catalysts supplied by Xpart also under perform, giving rise to the same fault indication. Changing the lambda sensor is unlikely to make any difference. Soon be time for a replacement I suspect. TC

21st August 2009, 20:05	#3
Sosban Regular poster MG ZT 1.8+ Join Date: Feb 2009 Location: Barry, South Wales Posts: 81 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks T-Cut, looks like I'll have to start looking for a replacement then!

22nd August 2009, 08:40	#5
Sosban Regular poster MG ZT 1.8+ Join Date: Feb 2009 Location: Barry, South Wales Posts: 81 Thanks: 0 Thanked 0 Times in 0 Posts	I use a Scangauge II. It doesn't read values from the oxygen sensors by default, and I don't have the knowledge to program the unit to scan these sensors. Thanks for the info.

22nd August 2009, 17:27	#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	My car had a new cat fitted 1 year and 6K miles ago and still gets code 0420 when the EML comes on. I just reset the light and as the car has passed 2 MOT's since fitting I am reasonably happy that all is OK. However I could be wrong. Have an emission test and see what shows up-should indicate the condition of the cat.

23rd August 2009, 10:23	#7
Sosban Regular poster MG ZT 1.8+ Join Date: Feb 2009 Location: Barry, South Wales Posts: 81 Thanks: 0 Thanked 0 Times in 0 Posts	Had my MOT only last month, with no probs. ECU warning light hasn't come on again, so I think I'll wait a while to see what happens.

8th April 2019, 13:05	#8
Greccehus1 Regular poster Rover 75 Saloon Join Date: Oct 2018 Location: Ophemert Posts: 33 Thanks: 0 Thanked 5 Times in 4 Posts	I recently had some problems with an exhaust valve fixed. Engine runs as smooth as you like, but now the P0420-code spoils the fun. Is it unwise to keep on driving with this problem (just because the valve problem wasn't solved cheaply )?

8th April 2019, 16:24	#10
Greccehus1 Regular poster Rover 75 Saloon Join Date: Oct 2018 Location: Ophemert Posts: 33 Thanks: 0 Thanked 5 Times in 4 Posts	Hi Glenn, thanks for your quick reply. The burned valve problem started mid January I think (misfire). The check engine light came on and first thing my garage did was replace the coil. This helped for two days or so and then the light came on again. I tried loads of things among which changing the plugs, changing coils again (some people on the Dutch Rover forum told me that Rover 75's can be particular when it comes to brands (Beru only), cleaning the stepper motor and using Wynn's cleaner products for injectors, valves, petrol system and cat. All to no avail. Another garage told me after checking compression that cylinder two had none. They didn't want to open the engine since they had no experience with the 1.8 turbo engine. I found a Rover garage who found out about the valve. 1.5 week later I was loads of Euro's poorer and as mentioned above a smoothly running engine richer. However, this morning I was unpleasantly surprised to see the light coming on again. Checking with TOAF showed the P0420-code AND even more irritating: I now seem toexperience trouble starting it; it takes a moment or two to pick up revs (are these two symptoms related?) The engine is like I said above a 1.8 turbo. Cheers, Jasper