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[Albatross]

I recently had an EML light on situation. I took it down to my local friendly mechanic who attached a cheap Tech2 device and we established I had an error 0421 (I think that was the number, but I've lost the peice of paper now)

I repeat and acknowledge; I may have got that number above wrong, but we looked it up in the code fault guide for the 3.2 V6 at the time and it said that the problem was exhaust fuel mixture related. Apparently the difference between the O2 reading before the CAT and the O2 reading after the CAT were not sufficiently cleaned enough.

It suggested a number of possible causes:

Fuel too rich
Lambda (O2) sensor problem
CAT problem

We cleared the orange warning light and then everything has been EML light free for the last 4 or 5 days until about 10 minutes ago coming home when it has come on again.

What's the 1st step and how do I isolate this problem and fix it without throwing money unnecessarily at spares I may not need?

If it is the lambda switch/sensor, how can I tell which of them and what sort of price am I looking at?

[Marks DTM Calib]

I suspect it was 0420....in which case ignore it as it will be the pre-cat getting tired but, wont affect any part of the emissions.

You could run some cataclean through it.

[Albatross]

I suspect it was 0420....in which case ignore it as it will be the pre-cat getting tired but, wont affect any part of the emissions.

You could run some cataclean through it.

It was 0420 now I think about it.

I don't want an orange light on my dash, it bugs me and what more important is that I won't know if it tries to tell me something else is worthy of a warning.

Surely the warning light is there to prevent you damaging your engine??

I remember TB saying something about this CAT too when he Tech2 scanned my miggy and fitted the CID.

How can i fix it? Do I need to replace?

The car's done 90K miles

[TheBoy]

Try cataclean as suggested, also better quality fuels may help.  It seems the precats are a bit rubbish on the 3.2s

[Albatross]

Try cataclean as suggested, also better quality fuels may help.  It seems the precats are a bit rubbish on the 3.2s

OK thanks, but now I have some quick questions:

How does cataclean work? (i.e. how do you use it?)

Will cataclean's effects last for any length of time?



Can I "de-cat" the preCAT from the car?

Is there a way of switching off the EML light for that error, but still have it work in case of other errors?

How do people who have de-cat straight through exhausts deal with the EML light issue?

What if I wanted to replace the faulty cat, any idea on the best route? new? refurb?

What sort of price?



Is my logic of wanting the EML light to be off, but still work to tell about problems unreasonable? I don't feel safe just "ignoring it", because I may be ignoring other issues.

[TheBoy]

I think it goes in tank, similar to injector treatment - it have helped some (but not all) people with this issue.

Not sure if anyone has decatted a 3.2 on here yet - the pairs of lamdas work in pairs to check the precat is working (presumably a sign the main cat is?)

No way to 'turn off for just this one code'

[VXL V6]

Don't think you can decat the pre-cats, the first lambda either side is responsible for mixture control.

TBH just reset the lamp whenever it gets on your nerves! Mine sailed through the emissions test on it's MOT today (As good as new apparently!) and the lamp comes on every 8 or so weeks. Cataclean will help (NB. 1 bottle to 15L of petrol) but it'll never be enough to stop the lamp completely.

[Kevin Wood]

Mine has started coming on more regularly of late. (at 60K miles). It seems to be the curse of all 3.2s.

On many but not all occasions it has done so a few miles after filling up from empty, with a cold engine, at an unusual petrol station. It does make me wonder if fuel trim has an effect and that suddenly changing some aspect of the fuel's quality makes a difference. It also always stores a fault for both banks (0340 and 0440 IIRC), suggesting it's something common to both banks. I have been trying to fill up only at my regular petrol stations, and only when the tank's 1/4 full rather than on vapours. So far it's worked (I just know the damned thing's going to come on tonight having said that!).

It's certainly nothing to worry about. TADTS.

Kevin

[VXL V6]

(0340 and 0440 IIRC)

Find it's P0420 and P0430 on mine.  

Running the scanner on mine seems to say that it's generating codes randomly before the light comes on (A threshold level has to be reached before the lamp is lit).

As said before, it's really nothing to worry about, the only time to worry is if the lamp flashes rather than stay illuminated.

[Kevin Wood]

Don't think you can decat the pre-cats, the first lambda either side is responsible for mixture control.

TBH just reset the lamp whenever it gets on your nerves! Mine sailed through the emissions test on it's MOT today (As good as new apparently!) and the lamp comes on every 8 or so weeks. Cataclean will help (NB. 1 bottle to 15L of petrol) but it'll never be enough to stop the lamp completely.

 

The mixture control lambdas are before the cats, so they don't actually care if there's a cat downstream of them or not. The engine will run quite happily if the mixture control Lambdas are present but the cats removed. You will get an EML unless the cat efficiency Lambdas see activity while the cats are cold, and see that activity cease as the cats come up to temperature. Only way around that I can see is to make a circuit to generate a signal to fool the ECU (I may well do that just to stop the damned light coming on).

Kevin

[Kevin Wood]

(0340 and 0440 IIRC)

Find it's P0420 and P0430 on mine.  

Yep. them's the ones.  

Kevin

[Marks DTM Calib]

Or re-position the sensors after the main cats.....mgiht not get hot enough though.

[Kevin Wood]

Or re-position the sensors after the main cats.....mgiht not get hot enough though.

That's a point.   The sensors are heated so it might work.

My WBO2 works from a cold start if you let the sensor heat up before starting. (not recommended as any condensation in the exhaust will kill it)

I assume the ECU has a timeout after which it expects the pre-cats to be up to temperature. Not sure the main cats would be working that soon, but it can't make matters any worse. In any case, it might not be the warmup issue that throws the fault code. Could be that the pre-cats lose effectiveness under heavy load when gas flow is high.

Kevin

[Marks DTM Calib]

Yes, should be reasonably straight forward to weld an extra set of boses in after the cats as a trial.....you can fit bungs (sump plugs) in the old holes and swap them as required.

[TheBoy]

Wonder if slapping the latest engine firmware on would help?  Has anyone got the latest on yet, and still suffering?

[Kevin Wood]

Wonder if slapping the latest engine firmware on would help?  Has anyone got the latest on yet, and still suffering?

I'm more than willing to be a guinea pig next time our paths cross.

I would imagine if this sort of thing started to happen to higher mileage cars under warranty the temptation for VX to tweak the firmware rather then replace umpteen cats under warranty would have been great....

Kevin

[Marks DTM Calib]

Unless there is a newer one in the 2008 TIS then Bob Dent has it on his....

[VXL V6]

Got the latest on mine (Unless there is a newer one than last August). You checked it when you did the climate and Autobox Mark.

[TheBoy]

Unless there is a newer one in the 2008 TIS then Bob Dent has it on his....

If only I knew how to find out  

[TheBoy]

Wonder if slapping the latest engine firmware on would help?  Has anyone got the latest on yet, and still suffering?

I'm more than willing to be a guinea pig next time our paths cross.

I would imagine if this sort of thing started to happen to higher mileage cars under warranty the temptation for VX to tweak the firmware rather then replace umpteen cats under warranty would have been great....

Kevin

Remind me for a freebie upgrade at lakes, or before if we meet before

[Kevin Wood]

Thanks Would be nice to try although it's looking less likely unless something came along in 2008.  :-/

Meanwhile I'll keep my eye out for some Lambda bosses.

Kevin

[Albatross]

Or re-position the sensors after the main cats.....mgiht not get hot enough though.

My orange EML light comes on after about 2 days and I don't have the ability to clear it myself.

Am I looking at a weld job on my exhaust?

What if I wanted to replace the faulty CAT, any idea on the best route? new? refurb? What would this cost?

How about I just go to longlife, get them to build me an exhaust which already has the extra bosses?

Wouldn't it be an idea to replace the faulty CAT? Perhaps I could get this as a different sort of CAT that might last longer?

I just want the problem solved properly really.  :-/

[Kevin Wood]

It seems like the problem is a design issue rather than a faulty cat. A new cat might temporarily solve the problem at considerable expense but as soon as its' efficiency has dropped a little it'll be back. A 2nd hand cat is unlikely to be any better IMHO.

The problem doesn't affect MOT emissions as the main cat is more than adequate so I'd say the best policy is probably to live with it. :-/

It would be interesting to try the relocation of the Lambda sensors but probably only on one car until it's proven to work.

Kevin

[Albatross]

It seems like the problem is a design issue rather than a faulty cat. A new cat might temporarily solve the problem at considerable expense but as soon as its' efficiency has dropped a little it'll be back. A 2nd hand cat is unlikely to be any better IMHO.

The problem doesn't affect MOT emissions as the main cat is more than adequate so I'd say the best policy is probably to live with it. :-/

It would be interesting to try the relocation of the Lambda sensors but probably only on one car until it's proven to work.

Kevin

Is there a volunteer for this yet? (I can't weld) , but I'm happy to donate my car as a ginuea pig if it can be put back afterwards and bunged up properly.

If I got a new exhaust built by longlife soon, they'd be able to design this in won't they? (Assuming the test is successful obviously)

[Kevin Wood]

It seems like the problem is a design issue rather than a faulty cat. A new cat might temporarily solve the problem at considerable expense but as soon as its' efficiency has dropped a little it'll be back. A 2nd hand cat is unlikely to be any better IMHO.

The problem doesn't affect MOT emissions as the main cat is more than adequate so I'd say the best policy is probably to live with it. :-/

It would be interesting to try the relocation of the Lambda sensors but probably only on one car until it's proven to work.

Kevin

Is there a volunteer for this yet? (I can't weld) , but I'm happy to donate my car as a ginuea pig if it can be put back afterwards and bunged up properly.

If I got a new exhaust built by longlife soon, they'd be able to design this in won't they? (Assuming the test is successful obviously)

I guess if you're planning on having an exhaust made that could be incorporated but I'd probably be inclined to keep the front cat sections and have them make a cat back system.

It only really needs one side modified as a test - just see if it removes one of the codes. Presence of the code on the unmodified bank will confirm that it's solved in the presence of the conditions that caused the original error.

Not sure if a boss could be welded on in-situ or if the exhaust would have to be dropped. Ideally Lambda sensors should be mounted above the horizontal, especially if they're in a cold section of exhaust, to prevent condensation from blowing onto the (heated) element and causing it to crack. Will have to have a peek under the car.

Kevin

[Albatross]

It seems like the problem is a design issue rather than a faulty cat. A new cat might temporarily solve the problem at considerable expense but as soon as its' efficiency has dropped a little it'll be back. A 2nd hand cat is unlikely to be any better IMHO.

The problem doesn't affect MOT emissions as the main cat is more than adequate so I'd say the best policy is probably to live with it. :-/

It would be interesting to try the relocation of the Lambda sensors but probably only on one car until it's proven to work.

Kevin

Is there a volunteer for this yet? (I can't weld) , but I'm happy to donate my car as a ginuea pig if it can be put back afterwards and bunged up properly.

If I got a new exhaust built by longlife soon, they'd be able to design this in won't they? (Assuming the test is successful obviously)

I guess if you're planning on having an exhaust made that could be incorporated but I'd probably be inclined to keep the front cat sections and have them make a cat back system.

It only really needs one side modified as a test - just see if it removes one of the codes. Presence of the code on the unmodified bank will confirm that it's solved in the presence of the conditions that caused the original error.

Not sure if a boss could be welded on in-situ or if the exhaust would have to be dropped. Ideally Lambda sensors should be mounted above the horizontal, especially if they're in a cold section of exhaust, to prevent condensation from blowing onto the (heated) element and causing it to crack. Will have to have a peek under the car.

Kevin

Wouldn't welding an appropriately threaded nut onto the top of the exhaust pipe just behind the rear CAT suffice as a lambda sensor boss?

Then if this proves not to work an equally appropriately sized short bolt would work as a bung?

If someone who can weld wants to help test this out and isn't a million miles away from me is around, I'd be happy for a bolt to be welded to the top of my exhaust (one side) to try it.

By the way which side does code 0420 refer to?

[Kevin Wood]

Yep. The boss is effectively just a chunk of metal with the right thread on it.

Kevin

[Albatross]

No takers?

[VXL V6]

By the way which side does code 0420 refer to?

Bank 1 IIRC

Will let you know for sure when I next read mine.

[Albatross]

By the way which side does code 0420 refer to?

Bank 1 IIRC

Will let you know for sure when I next read mine.

Cool thanks, "bank 1"?

Is that right, left, port or starboard when it's at home? :-/

[VXL V6]

Nearside / Passenger side at a guess.

Depends how GM view their engine bays - from the drivers seat or from the front of the vehicle.

[Marks DTM Calib]

Nearside / Passenger side at a guess.

Depends how GM view their engine bays - from the drivers seat or from the front of the vehicle.

Nah, bank one is drivers side because it comes off the 1-3-5 cylinder bank.

[Albatross]

bttt.

Anyone know any good welders in the South East?

[Albatross]

Do you reckon swapping out the (apparently faulty) pre-cat for one of these on special offer from longlife might be a possible option?

http://www.longlife-exhausts.co.uk/performance/offers.default.aspx

[Kevin Wood]

Do you reckon swapping out the (apparently faulty) pre-cat for one of these on special offer from longlife might be a possible option?

http://www.longlife-exhausts.co.uk/performance/offers.default.aspx

I would stick with the original one, TBH. Non-genuine cats are normally pretty pants. They look like just the cats rather than the whole pipe section as well, so would probably have to be welded in, and they'll be just the main cat rather then the pre-cat as well.

My EML's back on. Seems to come on every other week these days.

Kevin

[Albatross]

Do you reckon swapping out the (apparently faulty) pre-cat for one of these on special offer from longlife might be a possible option?

http://www.longlife-exhausts.co.uk/performance/offers.default.aspx

I would stick with the original one, TBH. Non-genuine cats are normally pretty pants. They look like just the cats rather than the whole pipe section as well, so would probably have to be welded in, and they'll be just the main cat rather then the pre-cat as well.

My EML's back on. Seems to come on every other week these days.

Kevin

I just want to find someone who's capable of welding the "experiment" into my exhaust. I reckon I'll invest in an additional lambda sensor to put further back and extend the wiring out  to give it a try.

[Kevin Wood]

Do you reckon swapping out the (apparently faulty) pre-cat for one of these on special offer from longlife might be a possible option?

http://www.longlife-exhausts.co.uk/performance/offers.default.aspx

I would stick with the original one, TBH. Non-genuine cats are normally pretty pants. They look like just the cats rather than the whole pipe section as well, so would probably have to be welded in, and they'll be just the main cat rather then the pre-cat as well.

My EML's back on. Seems to come on every other week these days.

Kevin

I just want to find someone who's capable of welding the "experiment" into my exhaust. I reckon I'll invest in an additional lambda sensor to put further back and extend the wiring out  to give it a try.

Just find a sump plug or bolt of the correct size. Most Lambda sensors are M18x1.5 thread IIRC (I'll double check).

If you leave a Lambda sensor in the exhaust disconnected, it'll knacker it because without the heater it will clog up with carbon.

I would offer to help - I've got a welder, but need to learn how to use it properly before I unleash it on cars.

Kevin

[Albatross]

Do you reckon I'll be able to take the lambda sensor that's already in there out without busting it?

Every lambda sensor I've ever known that needed changing has almost become part of the exhaust.

If it comes out safely then obviously a bolt is a cheaper option.

[Kevin Wood]

Do you reckon I'll be able to take the lambda sensor that's already in there out without busting it?

Every lambda sensor I've ever known that needed changing has almost become part of the exhaust.

If it comes out safely then obviously a bolt is a cheaper option.

Give it a good soak in Plus Gas.

Kevin

[Albatross]

I suspect it was 0420....in which case ignore it as it will be the pre-cat getting tired but, wont affect any part of the emissions.

You could run some cataclean through it.

If I go and put some Cataclean through this and given that this is a 3.2 (late ECU) will the EML clear itself if the results are positive or will I need to get it cleared and wait and see if the EML comes back?

[Albatross]

Jaime,

You must know this one. :-/

If I clean my CAT will the EML light go out on its own or will I have to clear it with a reader?

Ta

Nathan

[davlad22]

^^^^^^^^^^^^
Thought you knew that as well Nath!?!

Most 'normal' EML errors disappear after the fault has been rectified or at the most, 20 successful starts?

That correct?

Is it the EML light though or the emissions light???

[Kevin Wood]

The Emissions light will go out of its' own accord when things are Ok for a certain number of engine starts. Takes a week or normal use to go out IME. The codes will remain in memory until cleared, however.

If using cataclean, bear in mind that the Omega's tank is pretty big and if you add it to a full tank you'll likely dilute it too much to make a difference. Have a look on the bottle for recommended dilution and try and get the tank at the right level.

Must try some of that myself.

Kevin

[Albatross]

^^^^^^^^^^^^
Thought you knew that as well Nath!?!

Most 'normal' EML errors disappear after the fault has been rectified or at the most, 20 successful starts?

That correct?

Is it the EML light though or the emissions light???

What's the difference between the EML light and the "emmissions light"?

The light I have (had*) is the orange one with the picture of the engine on it.

(*it went out again last night and has stayed off this morning )

[Albatross]

^^^^^^^^^^^^
Thought you knew that as well Nath!?!

Most 'normal' EML errors disappear after the fault has been rectified or at the most, 20 successful starts?

That correct?

Is it the EML light though or the emissions light???

What's the difference between the EML light and the "emmissions light"?

The light I have (had*) is the orange one with the picture of the engine on it.

(*it went out again last night and has stayed off this morning )

Until yesterday

Any welders?