12 pin GM ALDL

**Aaron1989** · 12-05-2022

I have a similar ftdi usb. I connected the rxd and txd together and ran them to the serial data (pin m) then ran the ground to the ground (pin a).

When I connect it to the car and get tuner pro opened up and start data logging the readings are erratic and are all over the place. I even tried putting a resister between pin a and b. And still nothing. With the key on engine off if I push the accelerator the volts for the TPS sensor raise.

I talked to a guy that used to be a mechanic and is an electrical engineer now and he said I may be able to put a diode on the rxd side with the positive facing the Aldl port. He said what it sounds like to him is that the signals are getting mixed up. And from other research I've done says that serial is the best way to go

92 Buick LeSabre 3.8

**Aaron1989** · 12-05-2022

Like I said I'm new to all this and I'm going to buy the cable from ALDLcable.com so I have one that is problem free. but i want to make one from scratch also. I have bought a kit with different types of diodes, transistors, resisters, etc and a breadboard to. I also bought a USB ft23rl, a DB9 serial connector and a serial to usb. If my schedule ever allows it I want to sit down and try to get one working good and compare my results to the aldlcable.com cable.

**kur4o** · 12-05-2022

There might be chatter on the bus and tunerpro adx can`t handle it.
I will try flashhack first to make sure it is not car or tunerpro related.

**Tunedperformance** · 12-06-2022

I have a limited supply of the moates xtreme aldl cables for sale

**NomakeWan** · 12-09-2022

Originally Posted by Aaron1989

I have a similar ftdi usb. I connected the rxd and txd together and ran them to the serial data (pin m) then ran the ground to the ground (pin a).

When I connect it to the car and get tuner pro opened up and start data logging the readings are erratic and are all over the place. I even tried putting a resister between pin a and b. And still nothing. With the key on engine off if I push the accelerator the volts for the TPS sensor raise.

I talked to a guy that used to be a mechanic and is an electrical engineer now and he said I may be able to put a diode on the rxd side with the positive facing the Aldl port. He said what it sounds like to him is that the signals are getting mixed up. And from other research I've done says that serial is the best way to go

92 Buick LeSabre 3.8

Since you have a Buick, there's a chance your car has a Body Control Module. If whatever program you're using doesn't account for that while trying to datalog you will have erratic data.

We have the same issue with Corvettes that have a Central Control Module. Your datalogger needs to be aware that there is a handshake which has to be done to transfer bus master control from the BCM/CCM to your datalogger before you can start requesting data from the ECM or other systems.