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Old 11-01-2009, 09:57 AM
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Qui-gon Qui-gon is offline
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Join Date: Dec 2007
Location: Lantana Fl
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I have dissasembled the interface and drawn out the circuit. The Tx line from the ECU uses part of a standard Maxim 232 Rs232 level convertor. The ECU side of the level converter has an extra pull up resistor giving the line in from the ECU a nominal voltage of +6v. This is with respect to ground which is common to both the ECU and the PC it is connected to. This part is most likely standard TTL to rs232 conversion, ie inverted and voltage converted. The Rx or input line to the ECU is slightly different using a single transistor with a diode clamp. I would guess that in the ECU there is some kind of differential bus tranceiver to either a RS422 or 485 microcontroller interface. As for the communication protocol used it is probably home grown or using a subset of one of the known ones.
With regard to your original idling problem try playing with the throttle body bleed past screw which is the one visible through the plastic cover over the throttle cable on the kickstand side.
The service port is a 3 wire connector located under the seat just behind the tank. Probably identifyable by a rubber blanking plug in it to keep dirt and moisture out.
Hope this helps
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