I recently bought the Auto-X-Ray ALDL plug and cable so that I could splice the ALDL plug on to my MAX232 cable I am in the process of making. The cable is relatively simple to make with the help of probably one of the most original (meaning oldest) Electronics engineers in the country, My grampa. I have about 45 minutes into building the cable and I hit a roadblock. The Auto X-Ray cable with the specified part number only has 5 Pins that actuallg plug into the ALDL port. The rest of the spaces are empty. Unfortunately I left the cable at my grampa's house so all I remember about it is that the A, B, D, and E spaces have a pin sticking out and the rest are blank except for the first space of row #2. Now I am using the Max232 schematic that was built by AKM electronics and modified by Craig Moates. That schematic uses a computer plug with many more than 5 connections made at the plug that goes to the ALDL port. How do I splice the ALDL cable onto that working max232 cable so that it will interface correctly with the ALDL and ECM, Laptop and scanning software? Maybe there was a post about this already but my searches turned up without a solid definition of what I need to do. Post a link to it if you have it or maybe spell it out on the BB as best you can.

Look at the schematic again, you should only need pins A & M at the ALDL. A is ground and M is data. You should be OK, M is the first pin in row 2...

Is there a list of what years used the E vs. M pins for data?

I thought that on my 88, it was the E pin that carried the data and never used the M pin.

I haven't had much luck using the E pins so I'll try the M.

I the E hasn't worked I guess I won't have an ECU melt down if M is doesn't work either.

After further review I see that I asked a pretty dumb question to begin with... But I have a few new ones.

Since I am using the ALDL plug, I would then eliminate the carside connections to the 25 pin plug at 14, 18, 22, and 25 as I see no reason why they are there when using the ALDL correct? They appear to be along for the ride when using the 25 pin plug. Am I correct?

Also, with this cable, I can't understand why it is that D3 and D4 are not 1N914 diodes. The 4148 seems in excess and doesn't seem like enough for the D1 and D2. Those I would think should have been somthing more like 1N4005 or somthing comparable. Perhaps just for simplicity in attaining parts?

Lastly, with this circuit, would a regular 7805 instead of 78L05 still work? We were worried that the 7805 voltage regulator would have too much amperage draw and would pop the diodes each time the cable was used.

If you break out the multimeter, you'll see that M is spliced off of E and go to the same pin on the ECM.

Thanks Jza!