Principle Of Operation

The ME 9.2 Engine Management System from the N62 engine provides the basis for the MED 9.2.1 Engine Management System.

The main distinguishing features of the MED 9.2.1 are:

• Extended computer capacity (additional 1 MB flash)
• Modified oxygen sensor chip which permits detailed diagnosis of the oxygen sensors
• One MED 9.2.1 control module for each cylinder bank
• Power is supplied to the high pressure fuel injectors for each cylinder bank by a high pressure fuel injector control module (HDEV)
• Omission of DISA and variable intake manifold activation (N62)
• Three knock sensors for each cylinder bank
• Activation of the auxiliary air flaps in the air cleaner housing
• Rail pressure sensor
• Fuel quantity control valve

An MED 9.2.1 control module is used for each cylinder bank. Both control modules are the same design and are classified into ECM 1 and ECM 2 by the programming. ECM 1 receives the input signals from a sensor or switch:

• Accelerator pedal module
• Oil condition sensor
• Alternator
• Coolant temperature
• Oil pressure

ECM 1 transmits these signals via the Local-CAN bus to ECM 2. All further input signals are transmitted directly to the control module responsible for the relevant cylinder bank (see overview pages 5 and 6).

Output signals which relate to not just one cylinder bank (e.g. electric fuel pump or exhaust flap) are transmitted by ECM 1 to the corresponding actuators. The crankshaft sensor signal is transmitted simultaneously to both control modules.

The MED 9.2.1 regulates the injected fuel quantity. For this purpose, the MED 9.2.1 receives the rail pressure sensor signals and regulates this pressure with the fuel quantity control valve according to the value defined by the program map. This ensures that a defined quantity of fuel is injected over the injection period.