Output Control Functions
OUTPUT CONTROL FUNCTIONS
FUEL PUMP RELAY CONTROL
ME 7.2 controls the fuel pump relay as with previous systems with regard to engine speed input for continual activation of the relay.
The ME 7.2 will switch off the fuel pump relay when an airbag is activated as an additional safety function. The signal is passed from the MRS III control module to the ME 7.2 over the CAN line
E BOX FAN CONTROL
The E Box fan is controlled by ME 7.2. The control module contains an integral NTC temperature sensor for the purpose of monitoring the E box temperature and activating the fan.
When the temperature in the E-Box exceeds predetermined values, ME 7.2 provides a switched ground for the E Box fan to cool the E box located control modules.
With every engine start-up, ME 7.2 briefly activates the fan ensuring continued fan motor operation for the service life of the vehicle. This feature is intended to prevent fan motor "lock up" from lack of use due to pitting or corrosion over time.
SECONDARY AIR INJECTION
Secondary air injections required to pre-heat the catalytic converters for OBD II compliance. The system consists of the same components as previous systems with V8 specific locations.
The DME ME7.2 control unit controls the vacuum vent valve and the secondary air injection pump relay separately but simultaneously.
The secondary air pump operates at a start temperature of between 10 °C and 40 °C. It continues to operate for a max. of 2 minutes at idle speed.
ME 7.2 contributes an additional correction factor for secondary air "on" time with the additional input from the integral ambient barometric pressure sensor.
This sensor provides a base value to calculate the air mass being injected into the exhaust system. This helps to "fine tune" the secondary air injection "on" time, optimizing the necessary air flow into the exhaust system which reduces the time to catalytic converter light-off.
AUXILIARY FAN CONTROL
The Auxiliary Fan motor incorporates an out- put final stage that activates the fan motor at variable speeds.
The auxiliary fan is controlled by ME 7.2. The motor output stage receives power and ground and activates the motor based on a PWM signal (10 - 100 Hz) received from the ME 7.2.
Similar to the aux fan in the E46 with MS 42.0 control, the fan is activated based on the following factors:
- Radiator outlet temperature sensor input exceeds a preset temperature.
- IHKA signalling via the K and CAN bus based on calculated refrigerant pressures.
- Vehicle speed
- Battery voltage level
When the over temperature light in the instrument cluster is on (120 °C) the fan is run in the overrun function. This signal is provided to the DME via the CAN bus. When this occurs the fan is run at a frequency of 10 Hz.
ELECTRONIC THROTTLE VALVE (EDK) CONTROL
- The throttle valve assembly of the M62 TU is an electric throttle valve (ED) controlled by an integral EML function of the ME 7.2.
- The throttle plate is positioned by a gear reduction DC motor drive.
- The motor is controlled by proportionately switched high/low PWM signals at a basic frequency of 2000 Hz.
- Engine idle speed control is a function of the EDK. Therefore, the M62 TU does not require a separate idle control valve.
EDK ADAPTATION PROCEDURE:
When a replacement EDK is installed the adaptation values of the previous EDK must be cleared from the ME 7.2 control module.
1 From the Service Function Menu of the DIS/MoDiC, clear adaptation values.
2. Switch the ignition OFF for 10 seconds.
3. Switch the ignition ON (KL 15). At approximately 30 seconds the EDK is briefly activated allowing the ME 7.2 to "electrically learn" the new component.
This procedure is also necessary after replacing an ME 7.2 control module. However, the adaptation values do not require clearing since they have not yet been established.