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[chrisr]

I had the radiator replaced on my 2002 petrol about two weeks ago and all has been well since. On Friday  I drove about 85 miles to my daughter's with no problem. Today I headed home and after about 5 miles the check engine light came on. Then the check coolant warning came up in the car. I checked and it was ok. I got home and the coolant was still ok but the check coolant level warning is still on. I put my OBD2 scanher on and it said the fault was P0420 but it wouldnt clear. I'm thinking I need to change the after cat  O2 sensor again as this solved the check engine light a few years ago but whats with the coolant level warning? Are they separate problems or connected? The car is still running fine.

[Doctor Gollum]

Separate problems. Did you remove the reservoir during the radiator change?

If yes, check the sensor plug.
If no, check that the float is still present and bobbing.

There should be a plastic washer over the top of the float. If this is missing it can potentially obstruct coolant flow.

Only guaranteed solution is to replace the tank.

[TheBoy]

If the float is OK, short out the connector plug with a paperclip and see if the message disappears. If it does, that's also a new coolant bottle.

The P0420 is indeed a common issue where the precats are tired.  Move the sensors rather than replace the cats with an even crappier pattern version

[chrisr]

New coolant tank and after cat lambda sensor on the way. Lets hope its not the pre cat one! Thanks guys.

[chrisr]

What did you mean by "move the sensors"?

[Doctor Gollum]

Might be under V6 engine in the guides but the issue and solution is well documented 

[Doctor Gollum]

The gist is that the system is too stupid to know where the sensor is actually located.

[YZ250]

What did you mean by "move the sensors"?

This shows how it can be done on a V6. 

https://www.omegaowners.com/forum/index.php?topic=90613.0

As for the coolant tank, did you check if the float had come adrift due to the aforementioned plastic washer coming off, or short out the plug connector before ordering a new tank?

[TheBoy]

2.6 and 3.2 have 2 cats per bank - a starting cat and a main cat.  The sensors are located each side of the starting cat, the first sensor is primarily for close loop emissions adjustments ("fuel trims") and 2nd sensor is primarily to monitor cat efficiency.

The cats fitted to 2.6/3.2 Omegas are pretty shit compared to the earlier V6s, and the starting cat is small, so degrades badly with use.  The main cat is generally "adequate" for the life of the car.

Hence, moving the 2nd sensor behind the main cat gives the sensor a fighting chance to read correctly.


Sadly, most of the modifications to the 2.6/3.2 from the original 2.5/3.0 are badly implementing and penny pinched.  The cats being one, but the biggest is removing the EGR, which means lowering the compression ratio to keep NOx emission in check, which is why the DBW ones are less powerful and less economical.

[Doctor Gollum]

Unless fitted with a proper gearbox

[ronnyd]

According to the poster, he has a Desmond.

[Doctor Gollum]

According to the poster, he has a Desmond.

This is true. However it's fitted with a similar engine managed system to the DBW V6 so the faulty codes are much the same

[TheBoy]

Unless fitted with a proper gearbox

Gearbox makes no difference to how crap (comparatively speaking) the engine is, as well you know.

[ronnyd]

According to the poster, he has a Desmond.

This is true. However it's fitted with a similar engine managed system to the DBW V6 so the faulty codes are much the same

Gotcha Doc 

[Doctor Gollum]

Unless fitted with a proper gearbox

Gearbox makes no difference to how crap (comparatively speaking) the engine is, as well you know.

I never had the inferior pre facelift technology in V6 flavour