An Obdii To Rs232 Cable allows you to connect your computer to your car’s Engine Control Unit (ECU) for diagnostics and data logging. However, connecting to older vehicles, like a 2001 model, can present unique challenges. In this guide, we’ll walk through a DIY solution for establishing a connection when the standard OBDII TX and RX terminals aren’t directly linked to the ECU. This method focuses on a V5/6 ECU, which requires a different approach for accessing its communication lines.
Bypassing Missing OBDII TX/RX: Direct ECU Connection
Standard OBDII connectors often include TX (transmit) and RX (receive) pins for data communication. However, in some older vehicles, these pins might not be connected to the ECU. This necessitates a direct connection to the ECU’s communication pins. For a V5/6 ECU, these are typically located on plug 136, pins 3 and 4.
Accessing ECU Communication Pins:
- Locate Plug 136: Identify the correct ECU plug. In some cases, this plug might not have any wires connected, leaving bare pin holes.
- Direct Soldering: Carefully open the ECU casing. Using a low-heat soldering iron, solder wires directly onto pins 3 and 4. These pins are often located at the top of the ECU for easier access. Exercise extreme caution when working with the ECU to avoid damage.
- Routing the Wires: Feed the soldered wires through the empty plug hole on the ECU casing (often the third hole). Drill small holes if necessary to accommodate the wires.
External Connection:
- Terminal Block: Use a terminal block connector to terminate the wires coming from the ECU. This provides a secure and convenient connection point.
- OBDII to RS232 Cable Connection: Connect the wires from the terminal block to your OBDII to RS232 cable, ensuring the TX and RX connections are correctly matched. Use different colored wires to easily distinguish TX and RX.
Important Precautions:
- Handle with Care: The ECU is a sensitive component. Take electrostatic precautions and disconnect the battery before working on the ECU or connecting/disconnecting cables.
- Low Heat Soldering: Use a low-heat soldering iron to avoid damaging the ECU.
- Verify Connections: Double-check all connections to ensure they are secure and correctly oriented.
Establishing Communication
Once the physical connection is established, software like Log1Call can be used to communicate with the ECU. This software allows for diagnostics, data logging, and other functions.
This DIY method allows you to bypass missing OBDII TX/RX connections and establish communication with your car’s ECU using an OBDII to RS232 cable. Remember to exercise caution and follow all safety precautions when working with electronics and your vehicle’s ECU. Consult with a qualified automotive technician if you are unsure about any of the steps.
