I Don't suppose the turbo would work properly if EGR valve stuck open.
Faults indicate that it has been stuck open and stuck closed or sticking
..that's if it has the rebuild-able EGR with stepper motor on it due to electrical fault or build up of carbon
note: EARLY EGRS ..not much written about them on the net at all ..they are a bit of a mystery. people replaced them as a whole unit. as they are un-serviceable ..well that is to the average person ...if you have a bit of mechanical aptitude; then nothing is un-serviceable.
The early ones look like this below - 2002 - 2007 or there abouts. note yours is 2008, not sure, dont think, they had TDDI's after 2007
https://bparts-eu.s3-eu-west-1.amazonaw ... 71287.jpegso more likely TDCI ..should have electric wires going to injectors, if so.
P0489 is a diagnostic trouble code (DTC) for "Exhaust Gas Recirculation “A” Control Circuit Low". This is a generic powertrain code, which means it covers all makes/models. These engine trouble codes refer to a failure in the EGR (exhaust gas recirculation) system.
The trouble code P0490 can be defined as Exhaust Gas Recirculation "A" Control Circuit High. If the powertrain control module would detect an extremely high rate of voltage flow within the EGR, then it would start triggering up the P0490 trouble code.
forget this one for now
Code P0645 is set by the PCM when it detects a general malfunction in the air conditioning relay control circuit.
P0489 is a diagnostic trouble code (DTC) for "Exhaust Gas Recirculation “A” Control Circuit Low". best explanation / symptoms and diagnosis can be found here.
more info here
https://www.obd-codes.com/p0489if the later stepper powered EGR TDCI and some TDDI'S ..you are dismantling ..cleaning, then, working out that it's still working .. if not, complete replacement
Early TDDI as pic above ..you are looking for used second hand ...or buying a updated one that looks nothing like the one fitted or the later ones, that nothing is written about it? no info at all ! or working out how to fix, it salvage it ..from zero information.
all the best.mark