EGR Problems | Exhaust fumes in cabin | VW T6 Transporter

We had a problem with the EGR system on the VW T6 Transporter. There were exhaust fumes in the cabin. The exhaust smell was due to a leaking EGR cooler pipe. We also replaced the faulty EGR temperature sensor. The is was causing an engine managment to be displayed with error code P040C and P040D.
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Van specification
VW T6 Transporter T28 SWB
102PS CXGB Engine
QWM Gearbox
PRORAM Induction Kit by RAMAIR
SOLOW NSL Coilovers by Transporter HQ
H&R Anti Roll bars / Sway bars
Powerflex bushes
Sportline bodykit
Gloss black upper and lower bumper grilles
Vanstyle LED DRL headlights
Transporter HQ tail lights
Van-X Gloss black gear surrond
Van-X Gloss black door grab handles
Useful links, Materials and Tools
Windows: www.stormvans.uk/
Sound Deadening: www.deadening.co.uk/
Insulation: www.deadening.co.uk/
Trim Tools: amzn.to/2HwVJEa
Ply Lining: www.customshopdesigns.com/
Carpet: www.harrisonstrimsupplies.co.uk/
Curtains: www.vanstyle.co.uk/
Cargo Nets: amzn.to/2UTJS66
Bed Foam: www.efoam.co.uk/
Inverter: amzn.to/2X7WbwS