For car enthusiasts, especially those who enjoy DIY projects, having a reliable Obdii-16 diagnostic cable is essential. This guide provides a step-by-step tutorial on modifying a standard KKL USB cable to create a functional and inexpensive OBDII-16 interface for BMW vehicles, specifically for use with diagnostic software like INPA, DIS, and SSS. This modification enables ignition detection, a crucial feature for in-depth diagnostics.
Understanding the Need for Modification
While generic KKL USB cables are readily available and often marketed for various car models, they typically require modification to work with BMWs. This is because the standard cable lacks the necessary circuitry for proper communication and ignition sensing. This guide addresses this issue by adding specific components to enable full functionality.
Parts and Tools Required
Before starting the modification, gather the following:
- A KKL USB cable (commonly available online)
- A 2n3904 NPN transistor
- A 220k resistor (values between 100k and 400k can also work)
- Soldering iron with a fine tip
- Solder
- A small piece of wire
- Small Phillips head screwdriver
Step-by-Step Modification Guide
Step 1: Disassemble the Cable
Carefully open the KKL USB cable casing by removing the four screws, typically two on each side.
Step 2: Bridge Pins 7 and 8
Using the small piece of wire, solder a bridge connection between pins 7 and 8 on the cable’s circuit board. Alternatively, you can directly bridge the pins with solder.
Step 3: Prepare the FDTL Chip
Locate the FDTL chip on the circuit board. Bridge pins 17 and 18 of this chip with a small amount of solder. This will serve as a base for the transistor.
Step 4: Prepare and Install the Transistor
Trim the legs of the 2n3904 transistor to approximately 1cm. Bend the two outer legs (emitter and collector) downwards, leaving a gap of about 2mm between them. Apply a small amount of solder to the tip of each leg.
Solder the emitter leg (E) to the bridged pins 17 and 18 on the FDTL chip. Position the collector leg (C) so it aligns with pin 20 of the FDTL chip and solder it in place.
Step 5: Install the Resistor
Cut one leg of the 220k resistor short (around 1.5cm). Solder this shortened leg to the middle leg (base – B) of the transistor. Bend the other leg of the resistor and solder it to pin 1 of the circuit board.
Step 6: Reassemble the Cable
Close the cable casing and secure it with the screws.
Conclusion
You have now successfully modified a KKL USB cable into a fully functional OBDII-16 diagnostic cable for your BMW. This cable will allow you to use diagnostic software to read and clear fault codes, monitor live data, and perform various coding functions. This modification provides a cost-effective solution for DIY enthusiasts seeking a reliable diagnostic tool. Remember to exercise caution when soldering and handling electronic components.
