The electronics of the Discovery Series 4, also known as LR4 in the USA and code named L319 are comprised of around 25 separate ECUs (nodes) which are all interconnected by high speed communication Busses. This allows them to interact with each other at high levels of interdependency, sharing information vital to their operation. A fault in any one ECU or its removal often has knock on effects in the others, with them storing bus error or missing node fault codes. Most of the ECUs use either a High speed (500K) or Medium speed (125K) CAN bus, which are both wired to the Diagnostic socket, these are also interconnected by the Instrument pack which acts as a built in gateway between the two busses. However the ECUs related to information or entertainment that might additionally have to exchange Video or Audio data use a special fibre optic bus called the MOST bus. This bus is not connected to the diagnostic socket but is connected to the Medium speed CAN bus through the main Audio Head Unit which again acts as a gateway.
High line or Low Line Audio
The Discovery 4 has 2 options for Audio equipment most noted by the head unit in the centre of the dash board. The High Line Audio head unit has a 3 x 4 button matrix immediately to the left of it's LCD display panel and the Low Line audio head unit has a row of 6 buttons underneath it's LCD display panel.
High line or Low Line Instrument Pack
The Discovery 4 can be fitted with either a High Line or a Low Line instrument Pack. The difference is that the high line Instrument Pack has a large LCD panel in the lower centre which is replaced with a set of individually illuminating symbols on the Low Line Instrument Pack. The following table shows the ECUs fitted to this vehicle.
For more detailed information about this ECU please click here.