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Author Topic: KWP2000 fast init on k line OBD pin#7  (Read 2467 times)
protomode
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« on: January 14, 2025, 03:31:44 PM »

Hi I am trying to use KWP2000 fast init over K line to communicate with a car ECU. I want to get basic data like RPM, temperatures, speed. I have made a simple transistor circuit to convert 3.3V to 12V logic. When the engine is off, the car's ECU responds most of the time and sends me 0 RPM but I get a response. Once I start the engine it stops sending initialisation response and RPM response back. It is as if the car's ECU stops responding with engine ON. I have tried to add a 50ms delay after each last ECU response with no luck. Are there any specific timing requirements for KWP2000 fast init based communication? Other off the shelf OBD2 readers work fine with the car. The OBD2 K line voltage in the car is about 3.3V at idle (ign ON) with no difference between engine on or off. Thanks.
« Last Edit: January 14, 2025, 03:33:24 PM by protomode » Logged
fknbrkn
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mk4 1.8T AUM


« Reply #1 on: January 15, 2025, 02:16:31 AM »

Better to use broadband can-bus messages for retrieving data from ECU
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gauiX4
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« Reply #2 on: February 04, 2025, 07:11:35 AM »

Hi I am trying to use KWP2000 fast init over K line to communicate with a car ECU. I want to get basic data like RPM, temperatures, speed. I have made a simple transistor circuit to convert 3.3V to 12V logic. When the engine is off, the car's ECU responds most of the time and sends me 0 RPM but I get a response. Once I start the engine it stops sending initialisation response and RPM response back. It is as if the car's ECU stops responding with engine ON. I have tried to add a 50ms delay after each last ECU response with no luck. Are there any specific timing requirements for KWP2000 fast init based communication? Other off the shelf OBD2 readers work fine with the car. The OBD2 K line voltage in the car is about 3.3V at idle (ign ON) with no difference between engine on or off. Thanks.

when you start the calculator restarts the communication from zero so you have to restart your fast init
At each start the calculator sends a pulse I no longer know if it is high or low to wake up the instruments connected to this OBD
so once the impulse is sent you have to start all over again you have to do a fastinite again to regain communication
« Last Edit: February 04, 2025, 07:16:04 AM by gauiX4 » Logged
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