Check Engine Light Flashing....Injector circuit open?

[lazyxj]

Have you tried using a noid light to check the injector's circuit?

 

[mcnamaag]

Yes. One of the first things. I figured out the issue and finally got it running right today. Fixes are;
1) Pin out the engine management harness. Found numerous bad spots and overall roasted wires. Especially around the injectors. Found new/used harness that was 90% serviceable and tracked down each wire from start to finish replacing or replacing them as needed. I'm OCD that way. If the prints say yellow wire white tracer I found a suitable, matching color and replaced it. Solder every repair and heat shrink. Rewrapped entire harness in protective casing, reinstalled the harness.
This fixed the intermittent flashing check engine light.
2) Pinned out the PCM and found that I had no continuity between pin 17 (#3 injector) and pin 15 (ground). I tried this both without engine running and battery disconnected, without engine running and battery connected, and with engine running and battery connected. I had continuity with engine running but it didn't "pulse". It was constant which is not a good thing. I had continuity with engine not running and battery connected also but I thought that might be normal. SO, I broke down and pulled a PCM from the same year as mine, i.e. 2000, 4.0, 4x4, automatic and swapped it in. BAM!! Lol. Problem solved.
All I can say is if you come across this issue with a check engine light and misfire code be sure you check your engine harness BEFORE you replace the PCM. There's a good chance that if I'd just tried to replace the PCM it would've been ruined by the shorted out harness and I wouldn't have realise it. Therefore, troubleshooting and never finding the issue, because I'd have thought it couldn't be the PCM, it's already been replaced.
I'm going to open up the PCM and try to isolate the bad circuit shortly but I wanted to post my fix in case someone else has a similar situation. Thanks to everyone for their suggestions!:cheers::cheers:

 

[lazyxj]

Thanks for the update.
One question. On the bad circuit, where injector was not pulsing, was the injector powered on or off?
Did the noid light up and stay on or did it not flash at all?

My 2001's injector wiring harness is cooked and I need to find a replacement.
I don't want to spend a fortune buying 6 individual plugs.
The 2000-2001 injectors have different plugs, than the older models, so pulling a used harness is either going to be cooked too or it will have the wrong plugs.

 

[mcnamaag]

It either didn't flash at all or it'd be intermittent. Realistically the plugs don't matter. So long as they have the correct end obviously. You could get them from several different jeeps they're not different between injectors. NOW, I do think the year matters as far as the connections go, but I found them at advanced auto for five bucks a piece. Your probably going to find that your harness is damaged at one of the pinch points. Around the back of your valve cover, coming out of the protective cover for the injector connections, behind the coil rail connection, etc. It's a bitch pulling the harness out of the jeep, ( in the driveway, 8" of snow, 20° outside), but I was able to get it out and back in without to much hassle. Honestly, I don't think I'd have been able to correctly identify and repair it in the jeep. Just make sure you warm up the harness before you try to reinstall it. I put mine next to the fireplace for about an hour or so, rotating it to keep it from getting to hot. I used a handheld thermal temperature gun to make sure it didn't get to warm. I warned the harness up to 120-125 degrees. That's plenty safe enough and it makes reinstalling much easier.

 

[mcnamaag]

What I'm trying to say is the injectors don't care if the connections are off a 2000 XJ or a 95 5.0 Mustang. So long as they fit. I have injectors from a Mustang in mine and they're plug and play.

 

[lazyxj]

What I'm trying to say is the injectors don't care if the connections are off a 2000 XJ or a 95 5.0 Mustang. So long as they fit. I have injectors from a Mustang in mine and they're plug and play.

Good point, had not thought of looking for Mustang injector plugs. They do use the same EV6 plug as the 2000-2001 XJs.

The 2001's harness is brittle and warming it does help when R&Ring it, although it's probably a little warmer here, today's high was 86.
.

 

[mcnamaag]

Lol. Jealous. But yeah, 5.0 injectors are a direct swap. So, if you need connections that's a good place to look.