Focus Mk2 - Very Low Mpg

[Olaf]

Hey guys.

I'm getting ridiculous MPG in my Ford Focus (2005, Studio, MK2). It's a 1.4 engine, and I'm getting around 23mpg in 70% motorway driving/ 30% city. I got around 320 miles in a full tank (55 litres I believe).

I went to a garage and had an expensive diagnosis done today that didn't help me one bit. Here's the results:

U1900 CAN Communication Fault - Receive Error Continous Memory Dtc

B1600 PATS Ignition Key Transponder Signal Is Not Received Continous Memory Dtc

B1320 left Power Sliding Door Latch Release Actuator On Demand Dtc

U1900 CAN Communication Fault - Receive Error ICM

P1000 On-board diagnostic (OBD) systems readiness test not complete PCM

The only problem with the car is that when idle, every few seconds the fan turns on very loudly and then turns back off. The engine was swapped a couple of months before as the previous one was pretty much dead.

Any ideas?