Most OBD1 US cars use the 12pin ALDL connector shown beside. If you have a car with the 12 pin connector this is the Interface for you !

Some older cars (such as early TPI's like GM 1227165 ECM, 1986-89 5.0 and 5.7 V8's) will require a
10Kohm resistor to be plugged in between pins A and B on the 12 pin ALDL connector in order to put
the car into "ALDL mode" and have the serial data start flowing. Our Interface have a slide switch
which can set pin B to different modi like connect pins A & B directly, by 10K Ohm or keep them
completely disconnected.

- Connects to RS232
- Power LED
- Robust casing
- Slide switch for change modi of pins A & B
- Uses reference levels for high/low signals so works on all cars without problems not like some
homemade interfaces
- Uses Motorolas MC33199 Transceiver at 5V ALDL levels not some homebrew solution
- Dual powered (can take power from RS232 handshake lines or over 12V cigarette lighter connector
cable what makes it superior over all other ALDL interfaces on market)

- ALDL Interface with 12pin plug
- 12V cigarette lighter connector to 2,1mm DC plug cable
- RS232 extension cable