Egr Valve/manilfold Clean Follow Up

[tubaman]

As you maybe aware from my previous posts, cleaning my EGR valve & inlet manifold prior to going on hols - made a big difference to the power/torque at low revs. I THOUGHT EVERYTING WAS FINE.

Whilst on hols after doing around 1500 miles of trouble free motoring, my car suddenly went in `limp home mode` in Germany near Koblenz. Luckily, I had my laptop/software and OBDII reader with me and the fault came up as P0400 (from memory) which was the EGR Valve.

Toyota main dealer put it on their meter (same diagnosis), cleaned the EGR manifold and charged me for 1.5hrs work (115 EURO) which both cured the fault and made me feel happy as I had expected a much larger bill.

They showed me a poor printout of a photo threy had taken that clearly showed some of the holes were blocked with Carbon.

What do you think has happened as I gave the valve a really good clean and the top part of the manifold (that the EGR valve sits on) a really good clean prior to my hols ?

Anyone also know which sensor/valve controls the regeneration process ?