I just pulled my 89 Firebird GTA with a 5.7 TPI out of storage to start dumping money into it again. However, I know when I put it away I was getting a SES code 13 related to the O2 sensor. I made a ALDL cable to try to pin point the issue and I am having some trouble that I cannot find the answer to. I am using WINALDL software. When I connect the cable to the ALDL interface with a 10K resistor and I put the key in the run position I get all 25 streams of data which is what you would expect. However, soon as I start the car the data become erratic and I get between 1 and 5 streams of sensor data and not 25 streams of ALDL data. I researched this but was unable to find a solution. Does anyone know what I am doing wrong? I have also tried using TunerPro RT without any success as well.

 

Do you have a ground wire connection in your cable?

 

Yes. I do have a ground wire. I made this cable

 

Are you using a different computer this time? Maybe a USB to serial adapter? True RS-232 signaling is -12V (not GND but an honest to God -12V) for logical 1 and +12V for logical 0. Adapters like this can be hit or miss depending upon the particular serial port implementation. You could try playing with R2's value by lowering it a little, this should make it less sensitive to noise coming from the ALDL pin.

 

I am using a different laptop than what I used before. I will see if I can obtain a different laptop and see if that works. I will report back tonight. Thanks for the advice.

 

It's a pretty common problem believe it or not. There are allot of obtuse applications for a serial interface like this.