Note: addition to BMW AG materials regarding PT CAN diagnostics: 2K Ohm), and correct function of BUS is endangered! The current leakage has to be eliminated and correct performance of BUS restored. If in the monitor of oscilloscope the signal is visible as depicted in previous material from BMW AG – there is a current leak between CAN BUS lines (around 1.
when BUS is active, CANH has to be +4,0. when BUS is passive, CANH has to be 0V CANL has to be +5V (important!). Sample – oscillogram on the right side of the image is correct (but does not corresponds to the graphical image on the left side).Ĭorrected places of the signal are marked with (1) and (2): Unfortunately, this material has some gross mistakes.įor example – the shape of K CAN signal from BMW AG material: E65 BUS Systems. terminal resistors: 820 Ohm (to +5V/GND) for “Basic” units, 12 KOhm (to +5V/GND) for others.īMW AG describes K CAN signal in their materials. data exchange speed: 100 kbps (or 500 kbps F01+). for reception and sending different ID numbers are used. if several units start to send data at the same time, the highest priority is for the unit, which has smaller serial ID number. each unit can start sending data at any moment. Active mode: >2 in typical case īasic performance principle of these data channels: Network diagnostics: Network voltage in passive mode should be: close to Ubat. This resistor for sure is located in Master module if the network contains also Power-up devices (which ensure “awakening” of the car) – also these devices contain such resistors (to ensure normal performance of the network in the moment, when the car “wakes up”). Network power supply, marked with red – terminal resistors, which are placed in current modules. Receiver: simple comparator (input = inverted), output: open-collector transistor. In the picture: simplified schematics of LIN BUS device transmitter/receiver part. After receiving directions, current device replies with network reply message. Network operation: Master unit gives directions for current device to reply. network load: power-up resistors in Master and Power-up modules. 
communication via 1 wire (active = low).These are slow (and not very secure – signal lines are not doubled) serial interfaces, that’s why they are used to control peripheral functions and management of mechanisms.
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