I keep getting the engine warning light coming on with the code P0420. I have replaced the gaskets on the exhaust manifold and turbo because they were blowing. It still came on so i replaced the 1st lambda sensor and the light still comes on. On one machine it states Catalyst system efficiency below threshold (Bank 1). On another less advanced diagnostic reader it stated recirculation temperature low. I was wondering wether it was worth cleaning replacing or if its advisable to do away with the recirculation valve. Or if you have any other advice on how to procede it would be greatly appreciated.
Thanks Rich

 

What year car? are you running cats?

 

P0420 is the OBD II code for a non-working or missing cat. Personally I'd think about re-mapping and getting rid of the light that way

The issue is with the 2nd lambda sensor which is being read by the ECU which then throws the CEL.

The 1st Lamda sensor (the important one) deals with closed loop fuelling.

Shaun

 

The car is a 51 plate GDA It has a 100 cell sports cat fitted and has already been remapped after the sports cat was fitted.

 

The code wasn't switched off by the mapper then, ask them to do it FOC.

 

Its been reset several times but keeps coming on. Does the code deffinately relate to the second lamda sensor because i was told it was the 1st lambda sensor.

 

Doesn't matter if its reset, it needs to be mapped out(so to speak).

 

nope its the second and explains, coz of the sports cat> I assume a de-cat up-pipe as well> can be turned of by your mapper

 

I will talk to the guy who remapped it. Thanks alot for your help.

 

P0420 is a well known code......and should have been sorted by the mapper... How much did you pay to have the front 02 sensor changed? they are not a cheap new OEM item !

By 51 plate GDA I guess you mean bugeye with Denso ECU and radio mast in the a-pillar

Shaun

 

I got the sensor fitted for £200 was told it wasn't working properly it did feel like the fueling was improved after it was changed. Yea its a bug eye with a denso lambda sensor.