DAF lorry help with emissions pressure sensor.

[Spottyappy]

I have a Daf LF, 2008.
The emissions warning light Came on, which my friendly local mechanic said is a plate failure,and only a DAF maindealer can fix.
£800 later, it had a gas sensor NOX and pressure sensor Ai/D replaced. I have no idea what they do or are!
Got it home. Started it about 3 days later, a big clunk from gear box area.
Then, this same thing happened twice more days apart when lorry cold but not when warm.
Rang DAF who said take it back. Did that last night. No clunk BUT the emissions warning light is back on.
They started it this morning, clucking and emissions light is off.
They tell me they don’t know what the issue is, but it’s unlikely to be related to the replacement they did. Since it was not clucking BEFORE they had it, I am not at all convinced it is unrelated but being mechanically stupid, I don’t know how I can prove it so any advise would be really appreciated. PM me if you prefer.
Hope this vaguely makes sense!
TIA.

 

[DabDab]

Um, well not quite sure of your question, but the Daf agents only changed a couple of sensors, so very unlikely to have caused the gearbox clunk.

But it is possible that there was nothing wrong with the sensors and there is a fault with the engine or emissions reduction system that they didn't sort out. How sure are you that it's a clunk from the gearbox?

 

[rifruffian]

In your mind, separate the emissions issue and the clunking issue.
Go to an experienced source, for example your Daf agent and issue to them your instruction to diagnose the location and cause of the clunking noise; be ready to pay for the time that will be involved