Hi,

1998 XJ 4.0L i6.

About 2 months ago I got a CEL.
Scanned codes...
I had a P0304 (cyl. 4 misfire).
Changed my spark plugs, was short on time about to go on vacation.
Cleared code.

She rode fine for ~ 2weeks. Then another CEL.
Scanned codes...
P0204 (Inj #4 open circuit) and P0304.
Finished my tune up job on her, cap, rotor, wires. (even replaced the platinum plugs with Champion copper plus like the manual says).

Figured I'd be ok for now.
CEL is back again, this time when I scanned codes...
P0204, P0205 (Inj. #5 open), P0206(Inj. #6 open) AND P0304.

I tested the Ohms at the injectors, 12.4 across the board.
Injector harness also passes ~12v. Visually inspected and all look good, no crimps or broken wires.

Can smell a slight fuel/gas in my exhaust (open injectors constantly sending fuel and not burning getting passed to exhaust)

Ummmm...I'm a bit lost on where to go with this?
Bad ground? Faulty ECU/PCM?

Annny insight would be great...

Thanks
-jb

 

CPS maybe?

 

Could be the ground side of the injector harness is shorting. The ASD supplies 12V to the injectors, the PCM grounds the other side to fire them. Check the wires between the injectors and the PCM.

 

Hi,

OK So I did a few things yesterday.

-Disconnect battery.
-Refreshed Battery ground.
-Refreshed dipstick ground.
-Cleaned battery posts.
-Disconnected PCM harness and cleaned with electric cleaner.
-Cleaned each injector harness with electric cleaner.

I followed the wire runs from the injectors through to the PCM. I popped the plastic cover off that houses the wire runs near the injectors. All appear well. After leaving the fuel rail area, they are loomed together and covered in conduit. Followed this back to the PCM. Unplugged and cleaned.

Now, upon looking at the electric schematic....


Now, I am getting power to each harness (test with a test light).

So I should double check the [DK GRN/ORG] wire running back to the PCM for anything odd? Should I check the BLK ground wire from the alternator as well?
(I'm not 100% awesome at following wire diagrams, so enlighten me if you can).

thanks.
-jb

 

The problem probably isn't in the common positive side, it's more likely in the injector negative side. See where each injector has a separate connection back to the PCM?
Wht/DkBlue
Tan
Wht/Yello
lt Blue/Brn
Gray
Brn/Dk Blue

That's where I'd look for problems. You'll have to peel away that plastic wire loom to see the wires.

 

Well, i think I'm gettin the hang of these diagrams.

Injector #4 connects to B16 on the PCM. When I cleaned the PCM connections yesterday, I only cleaned the black one. But from what I've dug up on a google search is that B16 is actually the WHITE connector into the PCM.



Is this correct? If so, I'll need to go back (when I have some time) a double check the PCM connections comming in.

So - the WHITE connector pin 16 is Injector #4....right?

thanks
-jb

 

Since it is flagging diff injectors, check the PCM grounds by cleaning and a volt drop test if possible. Next I would peel ECM open and look for a busted capacitor.... just me though

 

Hi,

Well here's a strange thing. After I did all this...

and I reset the PCM. I fired her up. She threw a code, I scanned ONLY 1 CODE...P0204.

I'll double check again to make sure it's still ONLY 1.

Where are the PCM grounds?

thanks
-jb

 

probably more, but heres a few..

 

Hey

Thanks for the pic. didn't realized you posted a reply.

I'm gonna take a peek at the ground and make sure everything is a-ok.
I got around to pulling at 3 plugs off PCM this weekend and cleaned em up real nice.

Still one code..p0204.

Ran like crap ever since then..realized this morning that I didn't plug the harness back in on #4 (dumb mistake). With the connector unplugged, I could actually feel the choppiness in the ride and a real tough idle. Lots of vibrations at low speeds when not on the brake.

I found the second set of o-rings for my injectors, so hopefully soon I can replace them.

Thanks.

 

About two months ago my Jeep was doing exactly the same - I tried everything you have and my particular fault turned out to be the TPS of all things! Wasn't expecting that.

Hope you get it fixed.

 

Hi,

Hmmm...interesting. I have yet to hear that one yet..TPS? some one also told me the CPS (crank).

Did you TPS exhibit any symptoms other than the ones I described? Were you getting P020x?? or were you just tossing money at parts until it was resolved?

thanks.
-jb

 

My Jeep was off the road for about 3 months because of this. It was throwing p0202 and p0203. I almost thought it was time to look for a new pcm as I ruled out issues with connectors, other sensors and wiring harness. All injectors were ohm tested and showed roughly 12.

I had other symptoms too. Torque converter unlocking itself when doing over 50mph then locking up again. Annoying!

The worst though was the bad misfire and really strong smell of gas. I had an aftermarket tps at this point and everything else had been ruled out. I had the tps tested and I was told it was giving off 'dirty' electrical signals. They were not quite within manufacturers tolerances and a side effect of this somehow was interfering with the pcm injector driver. The tps was replaced, codes cleared and has run fine since. Nothing else was replaced.

I have never heard of a tps causing this either. It's a jeep thing!

 

Hey,

Interesting. I'll check out my TPs using this procedure

3 cavaity connector, 1 is ground, 2 is signal, and 3 is 5v supply.

I'll see if it's within specs.

thanks
-jb

 

Ok,

So I ran the tests, with a digital meter (I know, should use analog).

Key ON and Engine OFF, back probed the black (ground) and the center, at idle I took two reading. First was 0.89v, and then a 0.90v. Seems like within specs (0.26-0.95v).

When I Wide Open Throttle (WOT) - I got a 3.90v reading. I believe specs is 4.49v.

Could this be the culprit of my P0204???

thanks.
-jb