2.5 Liter Diagnostic Connector with a Multimeter Help

[armyofchuckness]

Hey, guys.

 

I've spent the last two hours looking online for info on using a multimeter to use on the D1 and D2 connectors in my '86 2.5 liter MJ with no avail. I know that the ECU doesn't store codes. I know that Snap-On made a very expensive tool to read it. I know that you can easily test these systems with a multimeter, but I have yet to see anyone actually explain how! Even the FSM isn't particularly helpful to me. Here's what it says:

 

 

There's nothing on the previous or following pages that explains this further. Do I just connect one end of the multimeter to the ground terminal at D1-3 and check for resistance everywhere else? What's "Primary circuit test (D1-2) B+ after ignition" mean? I'm sure this is all really simple and I'm asking a really dumb question here, but if there's anyone that can help out with this, it'd be really great to have this explained somewhere on the internet for posterity and the other 2.5 drivers out there. Thanks so much!

[TheDude]

The older scanner is only $200 or so. I bought one. I've never heard of anyone checking the diag port with a multimeter though. Usually you test each thing directly.

[Eagle]

There's nothing on the previous or following pages that explains this further. Do I just connect one end of the multimeter to the ground terminal at D1-3 and check for resistance everywhere else? What's "Primary circuit test (D1-2) B+ after ignition" mean? I'm sure this is all really simple and I'm asking a really dumb question here, but if there's anyone that can help out with this, it'd be really great to have this explained somewhere on the internet for posterity and the other 2.5 drivers out there. Thanks so much!

As you go through the FSM to diagnose specific problems, if the problem can be diagnosed by use of a multimeter at the diagnostic port(s) it will be explained there. There is no single summary of all the tests on one page or in one chapter.

 

If you are trying to diagnose a problem with the FSM and there's no mention of using the diagnostic port -- there's a reason.

[armyofchuckness]

The older scanner is only $200 or so. I bought one. I've never heard of anyone checking the diag port with a multimeter though. Usually you test each thing directly.

Which old scanner did you get? I've only seen the Snap-On one that has the specific Jeep connectors. I'd spring for one at that price.

 

 

 

 

There's nothing on the previous or following pages that explains this further. Do I just connect one end of the multimeter to the ground terminal at D1-3 and check for resistance everywhere else? What's "Primary circuit test (D1-2) B+ after ignition" mean? I'm sure this is all really simple and I'm asking a really dumb question here, but if there's anyone that can help out with this, it'd be really great to have this explained somewhere on the internet for posterity and the other 2.5 drivers out there. Thanks so much!

As you go through the FSM to diagnose specific problems, if the problem can be diagnosed by use of a multimeter at the diagnostic port(s) it will be explained there. There is no single summary of all the tests on one page or in one chapter.

 

If you are trying to diagnose a problem with the FSM and there's no mention of using the diagnostic port -- there's a reason.

 

Thanks for the advice, Eagle. I thought I was losing my mind. Why show the diagram if they weren't going to show how to use it! That makes sense. Thanks again.

[TheDude]

It's the Snap-on MT2500.

You also need the 1999 Jeep cartridge and cable.

It basically gives you real time sensor data for everything.

Worth every penny in my opinion.