Tech Toy Hacks

Posted on Feb 5, 2014

The interface depicted below can be used build a serial cable to connect the serial port of the computer to the 16-pin OBD-II connecter found in many cars build in 1996 or later. This interface only supports the ISO 9141-2 / ISO 14230-2 K-line tranfer mode. If in your ODB connecter pin 7 (K-Line) is present and pin 15 (L-Line) is missing then this

Tech Toy Hacks
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interface will most likely work for your vehicle. This document describes the OBD-II ISO 14230-2 serial interface protocol. It has been compiled from various public internet sources. I have been successful building an ODB interface with this information, but no guarantee can be given that this information is correct. Use at your own risk. (in ms) 0-20 Inter byte timing in ECU response 25-50 Time between end of tester request and start of ECU response or between ECU responses 25-5000 Extended mode for "rspPending" 55-5000 Time between end of ECU response and start of new tester request, or time between end of tester request and start of new request if ECU doesn`t respond */ 5-20 Inter byte time in tester request Fastinit: _ _ _ _ \_/ //// //// 300ms 25ms 25ms packet response 1) Wait for 300ms with K line high. 2) Pull K line low for 25 +/- 1 ms 3) Let K line rise high and wait 25ms 4) init serial connection to 10400 baud, 8N1, 1=0Volt 0=12Volt, least significant bit first 5) send package c1 33 f1 81 66 33=dest, f1=our tester id, 81=start comms 6) wait for response 83 f1 01 c1 e9 8f ae 01=physical address, c1=response ok (7f=fail), e9=kb1, 8f=kb2 Slowinit: _ S _ 2 3 _ 6 7 _ _ _ \_/0 1\_/4 5\_/P //// //// 300ms 200 400 400 400 400 250 packet response 1) Wait for 300ms with K line high. 2) send a byte 33 hex at 5 baud. 200ms per bit startbit: 200ms low databit0, 1: 400ms high databit2, 3: 400ms low databit4, 5: 400ms high...

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