OBD won't communicate?

I'd probably start by checking the pins at the datalink connector. Pin 16 is battery voltage, pin 4 is chassic ground, I believe. I don't know if a scanner will say abort if there is voltage available? It doesn't hurt to check.

Thanks!
I checked the voltage to those pins...nothing. So I pulled every fuse one at a time and lo and behold, the OBD port is on the Cigarette Lighter circuit. Replaced that 15A fuse, and now it works.

Of course, now I'm troubleshooting a P0401 error code, restricted EGR flow...

Hey, good job, at least you can communicate with the computer. The cheapest thing you can do about that code is check for clogged passage, my info says if something is clogged, usually on the intake side of things.

Unable to retrieve DTC codes on OBD2, it displays error. Replaced computer with same results. Grounds and voltages present at computer. OBD2 good on all other cars. Does not have a pass key theft deterrent. Engine cranks good but will not start. Do you have any suggestions?

Will the scan tool power up off the cars obd2 connector?

yes obd 2 is powered up, data line is good, data ground line is good. Once in a great while I will get a read back, then it quits. OBD2 reads and goes into error. Fuel pump and injectors are shut off. Injectors at computer have 12 volts. Fuel pump relay a steady three volts,no pulse voltage. I have 40 years off electronics, and 50 years of mechanic work.

I posted the trouble tree for no com with scan tool follow the trouble tree and let me know what you find.

All those checks have been completed already and the pcm replaced with a working one from an other 97 venture. The pcm has 12 volts at pins c1-20,c1-19 and grounds at c2-60 c2-21 and c1-60,c1-19. Both the original and the replacement act exactly the same.

So then it really makes no sense then why a scan tool wouldnt work?If the scan tool works sometimes then more then likely you have a broken wire inside the insulation loose terminal somewhere etc.The scan tool your using works perfect on other cars?Also do have the proper fuel pressure injector pulse spark etc?

Sparks good .Fuel injectors and fuel pump are shut off. Will start if you squirt gas into the intake manifold. I tried to find the BCM to unplug, but its not where its supposed to be. The nova obd2 3100 shows that it is data linked.

The bcm isnt to the left of the glove box?Also do you have power to the fuel injectors at the connectors with the key in the run position?You dont have a scan tool that will read the bcm?

Yes there is 12 volts at the pcm from the injectors.and just a low voltage from the pcm to the fuel relay. All I found when I removed the glove box was 4 relays and a cable connector on the right side. Two articles that I read with my same symptoms found removing bcm plug allowed the obd2 to operate so I was going to try that.

The bcm is number 7 in the digram see if its there?

The body control module was there. It checked good, so started trouble shooting all over , used a one amp load to check supply voltages .I found the voltage at c1-20 dropped to zero when loaded to one amp. Started checking the voltage at the fuse, Opened up the wiring harness going to the computer and found batter acid fumes had gotten in to the heavy duct and was eating the insulation and corroding and eating away the copper wire. This spot was right over the top of the battery. Spliced the wire and was back in business with the car running. and the innova 3100f working showing trouble codes that may also be caused by the wiring.

Thank you
Don Retired Radar technician

Your welcome thats what were here for great find by the way let me know if the codes come back and you need any further info.