Quote Originally Posted by greggbruceauto View Post
what is MAX 232 -- this is the first it has been brought up.... I thought you said 'FT232' -- how does that differ from RS232?
I posted the links at the beginning of the thread -- the aldl cable I have was the standard when laptops still had serial ports. It was specifically made to use with OBD1 -- I find it difficult to believe it is such a rare bird now (and they still sell it brand new) since usb has become so popular .....that was the cable 'they' all said to use at the time --- how can it be it is so difficult to make that data enter into a newer computer -- they all still use windows, and they all still only understand 1's and 0's --- and it's STILL the same stream of data it was 14 years ago..... today's computers still understand touchtone phone sounds.... those have been around since the 70's .....and now they even have USB record players....
The problem is not the ALDL cable, or even necessarily the USB to serial cable, it's the way Windoze enumerates the port, and sets com speed (baud rates). The PC is looking for a certain rate of data exchange. With the non-standard buad rate of the GM ECM, trying to communicate with the USB to serial converter, sometimes packets get missed in either direction, and a loss of communication happens.

The only way to almost guarantee that the ALDL cable you have works is usually to buy a very expensive USB to serial adapter, which will be almost as much if not as much as buying a new USB ALDL cable.

There are other ways, as Robert is suggesting, to find specific converter chips, that you may be able to find at cheaper prices, but then you still have extra connections, as in the adapters, the power port plug, etc.

I am also part of the group that tried to make a serial ALDL cable work with a USB converter, without success. I made a MAX232 based ALDL cable years ago, that works with any native serial connection, in fact I still use it frequently with my test bench, since my desktop PCs have had native serial connections for a while now, or through the use of a PCI serial card. I gave up pretty quickly, and just bought the moates ALDL Xtreme about 8 years ago, and have never had an issue with it. I have used it on MANY cars over the years without issue, at least no issues that weren't user created. ;)