Technical MIL light comes on but no fault code

[4x4 MURVi]

OK, so actually a Peugeot, but same engine (?) as a similar vintage Ducato. I am in process of buying van and it had a throttle body replaced by garage to get through MOT (wondering if this was needed as indeed problem seems to persist!) Luckily, before I completed purchase MIL light came on again and was returned to garage. They advise no faults are logged, but MIL (engine management light comes one when driving) Any known likely candidates? Garage notes there are 4 wires on throttle body and loom, but only three corresponding on ECU. Garage also went into detail on CAN bus - with low reading 2.69-2.8, adn high at 4. (Not sure what all that means TBH.) Any throughts or guidance greatly appreciated by all concerned!

Peugeot Boxer 3.0 HDi II Typ 250 159ps, (2006 - 2011)​

 

[sumpplug]

OK, so actually a Peugeot, but same engine (?) as a similar vintage Ducato. I am in process of buying van and it had a throttle body replaced by garage to get through MOT (wondering if this was needed as indeed problem seems to persist!) Luckily, before I completed purchase MIL light came on again and was returned to garage. They advise no faults are logged, but MIL (engine management light comes one when driving) Any known likely candidates? Garage notes there are 4 wires on throttle body and loom, but only three corresponding on ECU. Garage also went into detail on CAN bus - with low reading 2.69-2.8, adn high at 4. (Not sure what all that means TBH.) Any throughts or guidance greatly appreciated by all concerned!

Peugeot Boxer 3.0 HDi II Typ 250 159ps, (2006 - 2011)​

I remember reading about replacement throttle body needing a modified wiring harness, hope i have got this right and it helps.

 

[4x4 MURVi]

I remember reading about replacement throttle body needing a modified wiring harness, hope i have got this right and it helps.

Hi- thanks for reply! Yeah, have read similar, but I think only applies where older vans are fitting the updated throttle body. Garage advises was like for like in my case. Mine was fitted with a Pierburg 7.01754.10.0 which shows as correct fitment for van. https://www.autodoc.co.uk/pierburg/7011392
Update is the MIL light comes on intermittently during driving and fault code P0638 recorded. I am wondering if it is the loom or connector whch is also corroded.