What is the ford transit immobiliser fault code 23?

If You're getting an immobiliser fault code 23 on Your Ford Transit Van, You're not alone; unfortunately, it's a relatively common error for the vehicle, and the signs that it points to are confusing at best. This is because it covers a wide array of problems; it's usually accompanied by other error codes (readable with an OBD2 scan tool) which will point to a more precise cause. You'll first want to peek around Your pump ECU (PSG), as this is one of the most common points of failure. Test the wires with a digital multimeter to the best of Your ability. If You're getting power to the pump and the relay, then You'll likely need to replace the pump ECU.