#DIY ALDL CABLE DIAGRAM SERIAL#

This circuit consisted of two transistors one connecting the 'ALDL data' to 'RS232 Receive', the other connects the 'RS232 Send' to 'ALDL Ground'. The ALDL cable with the male OBD1 connector shell will allow you to just feel under the dash and plug.

#DIY ALDL CABLE DIAGRAM SERIAL#

Since the first circuit performance wasn't great and the whole thing was messy, instead of refining the first circuit i thought i should try a new design. You can buy an ALDL Cable with an OBD1 12 pin connector shell, or OBD2 style 16 pin connector shell, or a cable with just a bare male pin, to plug into your cars female connector serial data pin location (pin M or E or 9 on the diagrams above).

Here is a picture of my harness wires that dont. Engine, trans and harness are all 1987 from a V10 (i think, whatever is 4wd half ton). This circuit worked, but for some reason the response was slow, i couldn't make it work with a Usb-to-Serial converter, and on some PCs you can't take power from Pin4 so you have to connect it to 12v external power source (the resistor stays). After frying 2 ECMs we decided there was a problem so we double checked the diagram we had been using and the wiring harness itself and found something didnt quite line up. The simplest ALDL interface circuit i could find consisted of one transistor and two 10k resistors it simply connected the data pin on the ALDL plug to the RxD(Receive Data) port on the RS232 on the PC through the transistor.

ДЄldl has a port for sending data and the RS232 on PC has a receive data pin (RxD) so the easiest way is to connect them directly but since each system uses a different voltage we should put a transistor between them. I've always wanted to connect my laptop to my GMC van OBD1 based ECU, a little research on the internet lead me to a simple circuit that could make that happen.

Diy aldl cable diagram