Did you test the pin that provides ground (since you are there?).

Yes...there is 2, checked them both, both were good... pin 3 and 4

 

Actually it was a post here in the forum I found while searching. It said to check pin 16 (12 power) and pin 3 and 4 for ground.

 

Stuff from CCKen especially re: Pins 4, 5, 6, 7:

https://www.cherokeeforum.com/f2/com...179930/index2/

 

3?

 

 

So, at this point,
all sensors are getting 5.5 volts
new cam sensor
new crank position sensor =both mopar oem
all grounds cleaned and renewed
new battery
all fuses verified good in power distribution and inside junction fuse block
all electrics work, windows, locks, radio, gauges lights, cigarette lighter etc..
tried to start engine in park and in nuetral.

no fuel pump hum when turning key on
no spark to spark plugs while trying to start
OBD2 bluetooth adapter states "ecu did not respond or ignition is off"

Is there a way to test the fuel pump?
Is there a way to test the PCM?

I assume the the AutoShutDown circuit is in play here..other than it not starting, is there a way to verify that or test for it?

OR does anybody know how to fix this, which would be more preferred than the intimate introduction into the diagnostic field of Jeeps.

 

oops my bad...4 and 5.....I checked 4 and 5 for ground not 3

 

Try disconnecting the TCM then reset/reboot the ECU.

Do you have ABS?

 

Ok, so I got a chance to check the diagrams tonight. I think I see one common factor that gets my attention.

Your symptoms are consistent with a failure of the A21 circuit coming out of the ignition switch. This circuit should be energized whenever the ignition switch is in the START or RUN position. Importantly it provides the positive control to the ASD relay (for spark) and positive control to the Fuel Pump relay. Interestingly, it also runs to the PCM so the PCM is aware of when you have the ignition switch in those positions. The PCM then provides the ground to the control side of the ASD relay and Fuel Pump relay (provided various other system conditions are met).

This could also keep the OBD2 scanner from connecting, because the PCM will never think the vehicle is in the RUN position.

You should take the Fuel Pump relay out and test the positive control cavity to see if it is energized when your ignition is in the RUN position. If it is not. You need a new ignition switch. Ok, to be thorough you'd probably want to check the A21 circuit at the ignition switch connector...its is the 12 gauge dark blue wire. (color code DB).

Given that you have ran the AC blower fan for years on max, I wouldn't be at all surprised to find out that the ignition switch finally failed internally. I had to replace mine for the same reason. Luckily, I caught it before it got really bad, but was able to test the resistance and see that it was way higher than normal. The 96 has what is called a "loaded" ignition switch, in that the full amperage of the AC blower fan runs through it. Yes...ponder that for a moment. On max, that is nearly 20 amps running through your boilerplate chrysler ignition switch. For years. It is probably one of the most dangerous circuits in the cabin as far as meltdown/fire risk goes. In 97, they finally switched over to a relay driven design that gets the main load off of the ignition switch.

Do you know how to identify and/or test the fuel pump relay like I mentioned? If in doubt, start with the ignition switch connector instead.

 

Tested fuel relay base cav 86
key off .01 volts
key on 11.90 volts
battery 12.36 volts

"Ok, to be thorough you'd probably want to check the A21 circuit at the ignition switch connector...its is the 12 gauge dark blue wire. (color code DB)."
Disconnected connector:
Ohms/resistance read at 29.4 on connector on dark blue wire
on switch ohms read O.L. with key off and key on.

 

Don't have abs....do I need to remove the lower dash to get to the TCM?

 

no abs, and do I have to remove the lower dash to get to the tcm?

 

Correct.

Also disconnect the battery at the ground before you pull the connector (I don't know why, but CCKen says to do it, so better do it).

 

ok, I tested cav 86 on both the ASD and the Fuel Pump relay in the Power Dist Box.

As I understand cav 30 on both will show battery voltage whether the key is on or not.
They both read 12.39 volts

As I understand cav 86 is switched to the ignition switch and power is determined by key position on or off.
Both cav 86 showed no volts with key in off position
Both cav 86 showed 11.89 volts with key on.

no hum from fuel pump when relay is installed and key is turned on

Is there a way to "turn on" the fuel pump to verify that it is operational?

 

Thanks for going through that methodically.

This definitely points back at the PCM not being happy about the conditions and never supplying the ground necessary to the ASD relay or fuel pump relay. Seeing if disconnecting the TCM brings back the CCD/OBD2 connectivity is as good a direction as any at this point.

If that doesn't produce any difference. Another test would be to make sure that the voltage on the A21 circuit (from ignition switch RUN/START) makes it all the way back to the PCM cavity (I'll have to look up that cavity when I get home). This is how the PCM knows what the ignition switch is doing.