94 Chevy TBI, Tunerpro, and OBD Diagnostics ALDL cable issues

My friend's 1994 Chevy 4.3 TBI pickup is having intermittent stalling and rough running issues with no codes set. Normally I'd say it's behaving like an EGR issue but swapping on a known good spare EGR valve didn't fix the issue. I decided to order an ALDL Cable from OBD Diagnostics and download Tunerpro to see what was going on rather than throwing parts at it. What should be a simple task... isn't (which always seems to be the case.)

Anyways, the problem I'm running into is that while device manager and the FTDI drivers show the USB Serial Converter and Virtual com port loading correctly Tunerpro will not recognize the cable and a simple Hyperterminal / Realterm direct com port connection shows no data coming from the com port with the key on. I've done some searching here and tried some of the suggestions regarding FTDI driver versions but so far no luck.

I've tried FTDI drivers 2.08.14, 2.10, and 2.12. All driver versions correctly recognize the cable and show up as a virtual com port in device manager. I'm aware of the possible issue with FTDI drivers version 2.10+ "bricking" counterfeit chips but the USB PID flag for the cable is still set as x6001 so I believe the FTDI chip in the OBD cable is genuine. Also, as far as I know FTDI pulled the "bricking" drivers down because of numerous complaints.

With any of the driver versions, when I go into Tunerpro to configure the interface cable (use plug-in, standard serial, select correct com port) and then hit "test for valid interface using settings" all of them give the "cable not found or not functioning" error. The cable is disconnected from the vehicle at the time. I've tried multiple com port numbers with 2.08.14, 2.10, and 2.12 FTDI drivers by changing the com port in device manager and then going back into Tunerpro to select the new com port and then run the cable test again. I've also tried 3 different laptops (2 with Windows 7, 1 with Windows 10.) Same result with all of them, they all fail the cable test in Tunerpro with all driver versions and multiple com ports.

I've also tried multiple ADX files (this truck should use an $0D mask) both from Tunerpro's web page and also the ADX library here. None will connect although I suspected none will since the cable doesn't pass the Tunerpro communication test. I've also tried this with and without the 10K resistor in place, on all 3 laptops, with all versions of the FTDI drivers, and with different com ports assigned.

Finally, I've also tried directly connecting to the cable while connected to the vehicle with RealTerm and Hyperterminal set to 9600/8/N/1 to see if I get *any* activity when the key is on... and nothing, just a dead screen.

Hoping someone out there might have a suggestion as I'm about out of ideas. My next step is to get a USB OTG cable to connect the OBD Diagnostics cable to my phone and try ALDL Droid. I still suspect driver issues and not a cable issue since the cable is rather simple and I doubt it's bad... although it could be. If the cable doesn't work with my phone I'll be ordering a new cable and returning this one.

I'd appreciate any suggestions, I'm sure a few of you have been down this path and might be able to offer a solution!

'94, is that still OBD1?

Wish I could help you, but I can't. I once tried using a Windows Vista laptop and the usb to serial converter with TunerPro and my truck which is OBD1 and it was nothing but heartache.

I resorted to using a Toughbook because of the serial port.

Maybe you can find a laptop with a serial port and try the cable with that?

The 94-95 TBIs still use OBD1 via the classic 12 pin connector.

Unfortunately the cable I have is direct to USB with the FTDI chip already installed, so no simple unplugging to try it directly on a serial port-- I'd have to cut the cable up. Also, my old circa 1998 laptop which still had a 9 pin serial port finally died a couple years ago.

USB to serial *can* work well, I've done lots of it for tuning and logging on Accel Gen 7, FAST classic and XFI, Pantera 882, Holley, etc, that all have serial communication. I have a USB to serial cable that I use for that stuff and it's worked reliably for years on multiple ECUs and laptops.

This particular case has me stumped because I've tried all the usual suspects. This morning before work I tried TTS Datamaster, no luck either. The USB OTG cable will be here tomorrow so I can try the current OBD Diagnostics cable with ALDL Droid. A friend down in San Diego is mailing me his known to be working Red Devil 12-pin cable to try. Hopefully I'll be up and running in the next couple of days...

Just thought I'd post an update... while I haven't plugged into the truck yet the new Red Devil cable passes the Tunerpro communications test. Looks like the cable from OBD Diagnostics is probably bad.

I returned 12 Pin ALDL OBD1 Bluetooth / Code Reader/ Scanner / Adapter I didnt get my money back for aldldroid. They didnt work on my droid or the laptop.

I connected the FTDI FT232RL USB to Serial adapter module USB TO TTL RS232 Arduino Cable 6Pin to the main wires behind the ALDL connector under the dash and to my laptop Running windows 10 with all the apps tunerpro, aldlscan ect works well. I purchased a Micro USB Male to USB Female OTG Adapter Converter For Android so I can use aldldroid with the droid and it also works.

The Red Devil cable worked perfectly, no issues with windows drivers, tunerpro cable test was OK, and it connected to the truck immediately.

Chasing other issues now. The PCM was showing a ton of knock retard even under light load which explained the sluggishness, it was pulling timing constantly and the somewhat slow decay rate of the knock retard meant the timing was extremely retarded almost all of the time once you started driving. Initially suspected one or two bad knock sensors, but pulled out the timing light and found that the timing was 5.5 degrees advanced for some reason. Reset the timing and that cured the knock retard-- logs now show only a slight amount of KR on the 1-2 and 2-3 shifts under heavy throttle. While the truck is running substantially better there are other minor issues; it still feels like it's down on power and it likes to die right after the first cold start (IAC maybe, even though IAC counts update properly and the pintle looks good and clean.)

I also can't figure out how the timing went 5.5 degrees advanced with no evidence of distributor movement... and when distributors are loose and slip it typically ends up retarding timing. Distributor shaft feels good without excess slop indicating a worn bushing that can cause the pickup to rub. I initially suspected a bad pickup in the distributor but it looks good on the scope and Tunerpro shows a steady RPM signal. At this point I'm suspecting an ECM that's starting to go bad.

Control module on the distributor messes with the firing order. The passing gear cable messes with my 1st and 2nd gear shifting, also gave me high idle on my 1993 GMC Sierra C1500 5.0 V8 Single cab short box.