I'm trying to get data from my '84 Duke to try and troubleshoot the cooling system and get more information on a stubborn stumbling issue, but the OTC 4000 scanner I am using, with the GM adapter and dataset, is not reading the data from the ECU.

The issue is that when I try to get data from it - Reviewing codes or the Datastream, it just keeps saying "Reading Data", and even letting it load for 20 minutes doesn't do anything.
The weirdest thing is that the same scanner worked just fine on a friend's '84 Trans Am with the 305 HO.

The 6 connectors and wires are all there, I have tried pushing them in more, wiggling and pushing in the connectors on the ALDL port and the ECU, and have tried it with the key "on" and the engine running. It's doing something because when I turn the key off or disconnect it, it says "No data at ALCL connector".

Any help in getting this working would be greatly appreciated!

Pull the console then ECM cover to see the PROM.

if isn't GM, the label will have other marks to nothing to maybe missing a label/tape over PROM erase window.
Many people and "Chip" companies block data stream to scan.

Scanner only see 1 temp sensor for that engine and often won't help if has coolant problems.

Can have crush pipes, dirt and more blocking flow.
Or if dash gauge just bounces in cold weather, likely nothing is wrong and can't get stant super stat anymore...
See my Cave, Thermostat, Crushed Pipe & rest of coolant section

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Thanks Ogre. He's just trying to confirm the accuracy of his temp gauge, as well as possibly find the source of an engine stumble at specific RPMs. I didn't think about a replacement PROM.

While I never seen a "Chip" for L4 doesn't mean it doesn't sold by anyone. "Chips" for V6 V8 and others were very common and many of them "deleted" data stream function.

Otherwise many think bad ECM or wiring but is an Iffy aftermarket "Chip."

ECT sensor and Gauge sender may not be =.
More so on Duke because reads different points.
But should show about same bouncing problem etc.

Can get IR, thermal couples and other types to read at/near base of T-stat tube that close = to ECT for ECM.