I need some help. I am trying to build an ALDL cable to hookup to my 165 ECU. I already have one that a buddy of mine made, but I want to make a new one to have as a backup.

I am using the 2 transistor schematic, but have a 2 questions.

Question is in red and Question 2 is in Blue.

Thanks.

Question #1 - All of those points should be grounded. Tie those points in where it says ground at either of the two connecters. Question #2 - That is a diode. I didn't use it for the cables that I have made and they all worked fine.

Excellent...I'll try that tonight

edit:

Does it matter what direction the transistors go in? and the diode?

It would be better if you make a max232 circuit ALDL cable. It's pretty complicated compared to the 2-transister cable, but if you are decent at soldering and can read diagrams, you should be able to handle it. I'll dig up the schematic if you want it.

Do you even need the 2 transistor for the 165? I was under the impression you could use the single transistor version. And I could never understand whats the benefit of an overly complicated cable when a simple version will do the same job.

From what I understand the single transistor is for 160 BAUD, I need the 8192, thus the 2 transistor.

BTW, it works. It took my sometime to build it (about an hour )but it worked first time I plugged it in.

I too don't really see the need for a more complicated MAX 232 board, especially since my soldering skills lack actual "skill"

This should work fine for me.

I taked to a couple EE guys here at work. They said the diod is not required but could potentionally help the circuit if your having voltage issues.

-- Joe

2 more questions:

1. Will this cable work for a 1994 LT1 Camaro ODB1?

2. Where would I put a LED to see activity on that circuit? See diagram below, that's where I think I should put it.

ttt....


So noone knows were to put an LED to light with data going through?

The cable will not work with OBD1. You can put the LED where you have it circled on the diagram. Why do you want an LED anyway?

You mean it won't work for the LT1 ECM/PCM, whatever it has. My car is ODB1 such is all 3rd gens...Can anyone else chime in on this to clarify.

The LED is for the coolness...just to see it light up when data is being transmitted.

Your circled points are for GND.

Correct, this cable will not work for 94/95 PCMs. It should work for the older stuff though, either 8192 or 160 baud.

Do not put the LED where you have proposed. Put it across where the RXD line ties into the transistor and GND if yuo're going to put it anywhere. Make sure you use a current limiting resistor though. It's just a bad idea to put a resistor in this circuit in any case, being as marginal as it is, but that's just my opinion. A cable that works is cooler than one with an LED.

i'll keep that in mind...i'll build a second one with the LED...don't want to mess up the one that works now....But I agree that function supersedes coolness....just playing around with this stuff and trying to learn....

My field of expertise in computer networking....not electrical engineering....


Thanks for the help