Pontiac Repair: Plug OBD scanner into DLC, and DIC, dash lights, and gauges go haywire, obd ii scanner, actron cp9175

Question
Hi, I have an Actron CP9175 OBD-II scanner. It works fine, I used it successfully on my other two vehicles before and after I tried it in the Montana.

I plugged it into the DLC on my Montana. It powers up, but it won't communicate with the computer. The "Driver Information Center" display cycles through all of its' displays (Low Fuel, Security, etc.); the ABS light comes on, and the gas gauge goes to empty while the scanner is plugged in. I checked the DLC, I have 12.5 volts on terminal 16, it grounds on 4 and 5, and 2 has fluctuating low voltage (less than 1V), which I take to be the output from the computer. From what I can find, this is the normal setup for the DLC. Behavior is the same with "key on" and with the car running. I'm stumped, can you help me?

Answer
Hi Steve:

what year van is this? 1996 or 1997? I belive one of those years had a glitch in the computer software that would not allow aftermarket scan tools to communicate with the engine computer. However you should be able to communicate with the antilock computer and air bag module. All the vlotages you noted are correct. If the scan tool will not communicate with the other modules I mentioned then I would say the issue is with the scan tool not the van. I'm not a fan of aftermarket test equipment. I have never used that tool before. some of the BIG BOX auto parts stores have tool rentals they may rent scan tools that would be your next option here.. What is the actual issue here with this van?