In the two transistor type there is no connection to the "B" pin on the ALDL but when using a MAX 232 there is. Isnt it needed?? why?

Is the MAX 232 "version" better than the other one or?

 

I use a simplified two transistor interface (one transistor)



Sometimes the 10k ohm from pin A to pin B is not included in the interface. That resistor is used to change the ECM mode of operation and is not really a part of the interface.

No connection - normal mode
10k ohm - ALDL mode
3.9k ohm - Factory test mode
short - diagnostic mode

Many ECM's output data in normal mode too and then you probably want to use that mode.

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Jonas Bylund


[This message has been edited by JoBy (edited November 21, 2001).]

 

Thanks..

Will it work on my ECM -89 MAF.

Why do many use the MAX 232 if it isnt better?

 

Both circuits "work" but the MAX is probably "better" as it should give a "quieter" line.