No communication with OBD2

Hey folks, its been a while since I have last posted here. The site has changed a lot but it looks good!

Anyways, I am really stumped here. I a working on a 96 Jeep Cherokee, this same car I have worked on before and scanned before without any issues. Customer reported that the MIL light came on at one point but after driving or more than a week it didn't come back one (it came one and went away). So I try to scan it, my scanner turns on and attempts to communicate but it just gets stuck at the page where the protocols are. It doesn't go any further. I tried disconnecting the Crank sensor cause I was told that it could short out and cause the problem but no luck. I have power and ground at the DLC. I can only assume that the SCI terminal isn't communicating? Anyways, is there any tests I can do? Is the PCM at fault?

The vehicle starts and runs properly?

Some of those early OBD2 Chryslers are picky. I've had some that wouldn't communicate with a pocket scanner but was fine with a Solus.
I see that you've worked on this one previously, I still would recommend trying a different tool.
You could probe the SCI pin with a meter and look for "something" between 0v-5v. A scope would be better as you would be able to see the communication and not just an average voltage reading of what's happening on that line.

kris.sondors wrote: Hey folks, its been a while since I have last posted here. The site has changed a lot but it looks good!

Thanks, sir! Glad to have you back

I'm with Noah, the 1995/1996 was a weird time for OBD communication, all sorts of problems.

Can you communicate with other modules, besides the PCM and ABS? If so, that'd isolate the fault to the SCI bus.

The SCI bus is on pins six and seven at the DLC, white and pink respectively. Like Noah said, there should be some voltage level there with a scanner plugged in and attempting to communicate. Taking the DLC loose of it's mounting may make the job easier.

Caritech wrote: The vehicle starts and runs properly?

I forgot to mention that, yes the car runs and drive fine. I pulled the IAT to throw a code but still can't scan it.

Noah wrote: Some of those early OBD2 Chryslers are picky. I've had some that wouldn't communicate with a pocket scanner but was fine with a Solus.
I see that you've worked on this one previously, I still would recommend trying a different tool.
You could probe the SCI pin with a meter and look for "something" between 0v-5v. A scope would be better as you would be able to see the communication and not just an average voltage reading of what's happening on that line.

I am familiar with those years being funky but the thing that throws me off is that I was able to scan it before with the same scanner. I have tried two different scanners with no success. I'll try to get my hands on another one to test it. Does the voltage have to be read with the scanner plugged in?

Tyler wrote:

kris.sondors wrote: Hey folks, its been a while since I have last posted here. The site has changed a lot but it looks good!

Thanks, sir! Glad to have you back

I'm with Noah, the 1995/1996 was a weird time for OBD communication, all sorts of problems.

Can you communicate with other modules, besides the PCM and ABS? If so, that'd isolate the fault to the SCI bus.

The SCI bus is on pins six and seven at the DLC, white and pink respectively. Like Noah said, there should be some voltage level there with a scanner plugged in and attempting to communicate. Taking the DLC loose of it's mounting may make the job easier.

Good to be back! I love the great community you guys have here!
Nope, I won't go past the the screen where it's searching for the protocols. I'll post a video of it today. So I should plug the scanner in and backprobe the DLC to see what voltage I'm getting?

Thanks so much everyone for taking the time to help me!

No problem! ScannerDanner attracts the smart techs, love it

So no comm with anything, eh? AND the scanner used to communicate. Hmmmmmm. Suspecting the SCI bus more and more, or possibly a spread pin at the DLC. Not saying you don't know how to plug in scanners or anything, just speculating.

In this case, yeah, the scanner needs to be plugged in and attempting communication to see anything. Newer Chrysler CAN systems are the same way, FYI.

Tyler wrote: No problem! ScannerDanner attracts the smart techs, love it

So no comm with anything, eh? AND the scanner used to communicate. Hmmmmmm. Suspecting the SCI bus more and more, or possibly a spread pin at the DLC. Not saying you don't know how to plug in scanners or anything, just speculating.

In this case, yeah, the scanner needs to be plugged in and attempting communication to see anything. Newer Chrysler CAN systems are the same way, FYI.

Yeah I can see that! I love it too!

Exactly. I visually checked the pins and they look fine to me, they don't look disturbed or spread apart.

Ah okay, I will do that next. I hope I have enough slack in the wiring to do it without making it a real headache!

kris.sondors wrote: Yeah I can see that! I love it too!

Exactly. I visually checked the pins and they look fine to me, they don't look disturbed or spread apart.

Ah okay, I will do that next. I hope I have enough slack in the wiring to do it without making it a real headache!

Ah OK, way ahead of me Had my fingers crossed for a simple spread pin, oh well.

Sorry if this turns into a hassle! There's not many times I have to do any serious testing at the DLC, but when I do, I ALWAYS wish I'd suck it up and buy a break-out box :lol: