ok. i just built a 2 transister cable,yes, i used all the correct parts. I even checked the schematic over ten times. Do i have a bad ecm? My ecm is a 730 with a hypertech chip FYI. Car runs good. Car was originally a tbi and the guy i got it from did the tpi conversion on it. My sel test with pins a and b work fine. I need to know where the data connection is at the ecm itself. I always thought the data wire on the aldl diagnostic port was an orange wire. On my 91 tpi 730 ecm car ,the data pin is supposed to be pin M. I have tried connecting with TTs datamaster, EFI live, GM moates ,freescan, and tunerpro rt with the correct bin files too. Anyone have any ideas? Please help

 

On the conversion he may not have moved the ALDL serial pin. TBI uses one pin while '7730 TPI uses a different pin. I recall TBI using pin E. And TPI using the pin that is opposite pin A.

You mentioned pin M on your '91 TPI, since I can't remember which is which at the moment, move pin E to pin M and it should work.

RBob.

 

What do you mean by move pin E to pin M? Do you mean simply just move the wire that is plugged into pin E from my data cable and move it to pin M on the aldl connector? I am using a 2 transistor data cable with a ground wire and a data wire coming off of it. the Ground wire is plugged into pin A on my aldl port and the data wire is plugged into pin M. I have also tried plugging my data wire into pin E (orange wire) on the aldl port.. I don't understand what you are telling me to do

 

A stock f-body TBI car doesn't have a terminal in location M of the ALDL connector. So I don't know what is there.

What should be done is to move the terminal that is at location E to location M. That is the orange wire and this is done in the vehicle ALDL connector. This way you can connect with any off the shelf scan tool.

RBob.

 

so you are telling me that a 91 tpi car should have an orange wire in pin m of the aldl port?

 

Yes.

RBob.

 

ok, so today, I switched the pins e and m around. Now pin M is directly under A (ground) like it should be. I even went as far as to connect a wire directly to the A8 pin ( serial data) on the ecu itself! Still no pcm found in TTS Datamaster. I even re-seated the prom in the ecu. I am using the 2 transistor circuit and it IS built correctly. I am at a loss here. Do the serial port cables not work as good as the usb design? I am thinking that maybe i need to go and buy the actual usb to aldl interface cable. I did verify my ecu. It is the 730 model with hypertech prom #122322. Do you think my cable is still the culprit? Anyone??

 

doesnt that cable need a power source to work?

 

yes, i am running it off of a 12v source.

 

Rob, is it possible that i have a bad ecm? Like i said before , I connected directly to the serial data wire on the ecm itself and still cannot connect. The car runs good though. Maybe a bad ground somewhere in my harness? Any thoughts?

 

UPDATE: Issue solved, it was a bad ecm. I became aware of this after i found low voltage on aldl Pin M. Should have been 5v on orange wire on pin M.