Communication with DME/DDE
The control unit output DME-KO is used to send the signals to the DME. The individual switching stages are transferred by way of pulse width modulation with a frequency of 5 Hz.
The standby signal of the air conditioning system (DME-AC) and the A/C compressor request signal (DME-KO) are transferred to the DME on a transfer line with the aid of pulse width modulation (PWM signal).
Pulse duty factor in % |
Functions |
|---|---|
0 |
Short to U-batt. or line break |
15 |
Air conditioning off |
30 |
Air conditioning standby (DME_AC) ON |
45 |
A/C compressor ON, stage 1 = 5-10 Nm |
60 |
A/C compressor ON, stage 2 = 10-15 Nm |
75 |
A/C compressor ON, stage 3 = 15-20 Nm |
90 |
A/C compressor ON, stage 4 = 20-24 Nm |
100 |
Short to ground |
Diagnosis of the line is carried out by the DME.
The conventional interface is coded as standard on diesel vehicles. The signals DME-AC, DME-KO and DME-KOREL are transferred to the DME via 3 separate lines. The coding determines whether the signal to be evaluated is active-high (12V corresponds to ON, 0V corresponds to OFF) or active-low (0V corresponds to ON, 12V corresponds to OFF). This coding should be read out via "read coding data" under "service functions".