I have a 2007 coupe 2.7hdi. Currently trying to sort out a pollution control system faulty issue. The code reader diagnosis says (amongst other things) that "air temperature after exchanger signal plausibility". I assume this involves the air temperature sensor but I'm not sure where it is. I'd be grateful for some guidance. Thanks. btw it's also telling me that the MAF readings are inconsistent - I looked at the airflow with the engine running - the front MAF has far lower readings than the rear - so I guess one of them is faulty.