P20EE Error code - NOx catalyst below threshold

P R

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Got the dreaded engine warning light on this morning. Read the code, P20EE which google tells me is the NOx catalyst is below thrshold value. So thats that then lol

Could be many things including NOx or T sensors. Has anyone had this fault code that could point me to a likely fault?

Grazie
 

P R

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I cleared the code (so the light has gone) however, its showing as a permanent code, which I read means that will clear when the issue is fixed?
 

P R

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Part of me now thinks its effectively deleted as there are no other warning lights (for now anyway) so whether the system is working as it should or not theres nothing spoiling? (ie its like its already covered by the permanent code)
 

matt_s

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Its the DV6 Ghibli.. its in for service in the next few weeks..
Ok. We’ve had this code on a few diesels lately (not Maserati), most common issues tend to be with the ad blue injector themselves. Had one recently that was completely blocked and triggered this code.
 

P R

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Ok. We’ve had this code on a few diesels lately (not Maserati), most common issues tend to be with the ad blue injector themselves. Had one recently that was completely blocked and triggered this code.
Great, thanks for that. Will mention it to my mechanic when its in
 

Steve4200

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I'm never sure what 'permanent' means :(

C
Pending = May clear on its own or trigger Stored after set number of driving cycles.

Stored = Will trigger code and warning light. Both can be reset and will return if fault persists.

Permanent = Will trigger code and warning light. Only the warning light may reset with the permanent code remaining. Warning light will return if fault persists. Code will only reset if repaired and/or set number of driving cycles are satisfactory.

Permanent was introduced 2009 ish to prevent codes and warning lights being reset just before test centre checks. The test centre will always check for permanent codes in countries that require full mandatory emission compliance.

Regards
 
Last edited:

CatmanV2

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Pending = May clear on its own or trigger Stored after set number of driving cycles.

Stored = Will trigger code and warning light. Both can be reset and will return if fault persists.

Permanent = Will trigger code and warning light. Only the warning light may reset with the permanent code remaining. Warning light will return if fault persists. Code will only reset if repaired and/or set number of driving cycles are satisfactory.

Permanent was introduced 2009 ish to prevent codes and warning lights being reset just before test centre checks. The test centre will always check for permanent codes in countries that require full mandatory emission compliance.

Regards

Thanks! How would the system 'know' if something's been repaired, other than the driving cycles?

C
 

CatmanV2

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51,409
Continuity check on the air bag circuit for example.

Hmm, not so sure about that. We know that if we unplug an airbag and it throws a light, it won't reset, even if you plug it back in. Might just be airbags of course

C
 

P R

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I'll check with the code reader again this weekend, see if the permanent code is still there. Im off on a long trip next weekend so should go through more than enough cycles to know if it was a one off or not..
 

Steve4200

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212
Thanks! How would the system 'know' if something's been repaired, other than the driving cycles?

C
If a sensor or cable is open/short circuit (ECU monitors circuits) then repair/replacement will be needed to reset warning light and code.

If sensor/system values are out of range then only successful driving cycles will allow code reset. Still could be a sensor fault but typically it will be failing emission control kit such as Cats, EGR, Nox, Air/fuel and Exhaust leaks etc.

For safety systems such as Airbag the warning and code will remain until repair/replacement as no driving cycles are involved, The ECU response is instant.

Regards
 

P R

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Still no return of engine warning light. I plugged my reader in last night and lo and behold no longer a permanent code either.

Fingers crossed it stays this way!!
 

P R

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Spoke too soon lol. Came back on last night. Same code, same behaviour (I cancelled the code, which cleared the light but has remained as "permanent")

What I did notice was that it came on during or immediately after a DPF regen. I know the 2 arent exactly related but the elevated temps might have had something to do with it.

Im off on a 600 mile round trip tomorrow so will see what happens next..
 

P R

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As way of an update, the code has not returned, and has disappeared from "permanent".
Its in for service at the moment and the mech has read it with his full diag tool and he also says theres nothing pending, permanent or any other indication of an error code.

I did start putting posh diesel in when all this started, which I I will now continue !
 

P R

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Took it in.. he plugged in his Maserati OBD whatever. He didnt think there was a sensor issue but thought it could be the DPF being high in soot (around 53%) effecting the NOx removal (Im assuming injection is upstream of DPF?)

Anyway, he did a forced regen, and at the end of it the soot level was down to 8%

He said run it and see, but he thought it wouldnt have let him do a forced regen with a dodgy sensor

The regen was brutal, first time Ive seen one. Basically the car went to 3k revs and stayed there for 40 odd minutes. The wet ground under the car was steaming and the heat coming out of the back was mega. Engine coolant temp was impressive throughout though, nothing wrong with that!!