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!
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