Diagnostic Scanner Help

Recently purchased a SNAP ON MT2500 Diagnostic Machine in the hope I can scan for any faults on my 91 GTO.
I have the MITSU-55 Adapater, data cable and Asian Imports thru 93 primary cartridge.

When I plug in to the port on the car with ignition or engine running I’m not getting anything. The scanner has new battery and is fully working.

Is there something I’m missing?

Any help will be welcomed from anybody with experience with these machines.

Hello. I just started lurking here after buying a '94 3000GT last week. But I made an account because no one has replied and I’m fairly sure I can help here.

I would start by manually entering OBD 1 mode the poor-man’s way first, to verify proper operation of everything. Seems a good place to start troubleshooting because we can immediately tell if the problem is the car or the scanner. Have you tried this?

The diag port is on the driver footwell fusebox if i’m not mistaken, Using a jumper wire clip on pin #1 the top left pin…clip the other end to pin #12 the bottom right pin…Turn the ignition key to on but do not start…The Check Engine light will blink in a series of short and long blinks…record that pattern and that will give you a code. 2 longs and 1 short is a 21 for example.

If the car doesn’t respond to this : it should. Inspect wiring for an issue first. If the car does respond - narrows down issue to your tool, or tool operation.


94-95 cars only blink the CEL for code retrieval.
91-93 cars sends pulses on the diagnostic port and no blinky CEL.

1 Like

Cool to know. The troubleshooting step is the same and it’s a good place to start because you can immediately tell which part has the problem, the car or the tool. Supposedly the tool is “on and working” but we don’t know if he/she has verified operation of scan tool on a different vehicle. Even if so, the mitsu adaptor could be bad.

If you’re interested, hook up an analog voltmeter and pull codes off the car. If the car gives codes via sweeping the analog meter (that can be picked up for $5-10 if you don’t have one) then that verifies the data link connector is good, and all the various wires, including the power (if applicable) and ground are all good. And that the inputs (sensors) are good and the wiring in between.

Supposedly the scan tool is working so I wouldn’t expect the car to correctly sweep the meter to show no faults. Then it’s just a matter of getting a pin-out of the connector and determining which pin has the problem.

Info on 1st gen OBD method: