Just bought severely neglected vehicle 2 months ago. Replaced coil, distributor, pick up coil, rotor, cap, wires, plugs, crankshaft position sensor, entire exhaust system incl both O2 sensors, and BK44 in the tank. Starts and runs fine (except fuel mileage) , but P1391 continues to trigger CEL. Blinker code yields 11, 12, & 56. NOT typo 56, double checked three times!

Old school techno dinosaur almost ready to cut my losses. Any revelations?

goodyoleboy

 

search the XJ archives for that code, there was a dude that persisted till the end with that code, was maybe a couple of years ago, about 30pages

I think it turned out to be either bad wiring leading to the cam sensor, or a duff cam sensor

mmm..i searched but could not find it, its there somewhere, did find this

1391 Code solved - Jeep Cherokee Forum

 

While the usual failure point is the sensor itself, sometimes it's the wiring. A bad/corroded connector, a broken splice, a shorted wire can cause these issues. I had a intermittent misfire in #3 due to a corroded splice to my #3 fuel injector that was buried inside the main harness.

While I don't have a revelation for you, I do have a link to the FSM that may help. Testing procedures, wiring diagrams, .etc..

https://archive.org/details/manuals_...ery=xj+jeep+96

 

Yeah, I should have elaborated on efforts so far.

Reading all the P1391 comments led me to try and find a replacement connector which Standard / Wells / Borg Warner does not / no longer makes. Apparently the connector style changed from pin to blade and the external shape /mating surfaces in the process, so I cleaned the connector with electronic cleaner, cleaned and abraded the interior of the female receptacle with a dental tool, dried with compressed air, compressed it for a better connection, and reinstalled it all to no avail. I have since order the new blade design connector to go with the blade style CPS purchased earlier by mistake.

The problem APPEARS to be temp related as I drove it about 10 miles very gently in the morning letting it warm up along the way with no CEL illumination. However, when I accelerated 1/4 mile from the house, the CEL came on almost immediately.

Does the metal part of the CPS also function as the ground? Kind of grasping at straws since the CEL illuminating is what led me to replace the CPS initially, but I'm wondering whether the rubber plastic shield around the sensor ( held in place by the metal T shaped frame) may be interfering with the ground?

Any insights will be greatly appreciated.

 

Well, if you can't find a replacement connector on one side, replace the other side to match. Or just solder splice the 2 together.

The CPS does not ground through the mounting plate. However, do double check your grounds. The manual has the locations of all grounds, splices and connectors in section 8w-90. The grounds begin with a "G" prefix. For example G101 is near the coil. Make sure all reasonably accessible grounds are clean and tight.

 

Yeah, that's kind of what I had in mind as soon as the replacement connector arrives. I'm new to this endeavor, so is "the manual" for ground locations here somewhere electronically, a book to buy, or ???

See message(s) above.

How do I access "the archives"?
What is a "duff cam sensor"?

Thanks
goodyoleboy

 

Go to this link: https://archive.org/details/manuals_...ery=xj+jeep+96

Click on the cover image. In the upper left corner, you'll see a circle with 3 dots (ellipses icon). Click on it and you should see "Downloadable Files (2 formats). Click on it and select "Get PDF".

Not sure what "duff" refers to but the cam sensor is inside the distributor under the rotor.

 

Code 11: No crank reference signal detected during engine cranking. Intermittent loss of either camshaft or crankshaft position sensor.

Code 12: Positive battery input to PCM was disconnected within the last 50 Key-on cycles.(normal to see this)

I don't see a code 56. Are you sure it wasn't 55? Code 55: Completion of diagnostic trouble code display on the malfunction indicator lamp (check engine lamp)

 

Yeah, I know, hold their hand, powder their bottom, kick em in the . . . :-)

See comment by AWG on Mar 2016 (above) re Duff cam sensor ? ? ?

My understanding (such as it is) is that the pick up coil and the "cam sensor" are one and the same and in this case already replaced.

I have a DTC scanner w/ erase function, but I'm sensing ( get it? :-) ) that I'll be needing one with more bells and whistles going forward. Any guidance for this techno-dinosaur?

Thanks
goodyoleboy

 

Well, the plot thickens.

Page 107 of the archive linked manual (referenced above) shows two configurations for the crankshaft position sensor connector #C117. One has the 5 volt power supply on the right for the "Early Build" and the other has the power supply on the left for the "Late Build", but there is no explanation of what constitutes early or late. Mine was built in November.

Heaven forbid this should be easy.

Thanks
goodyoleboy

 

It would not run if you have the power wires wrong

with respect to the crank sensor, you should measure the exact thickness compared to the original one with a vernier, and also test its magnetic strength by lifting spanners etc

I dont know what sensors you have, but the crank sensor in particular the aftermarket offerings are known to be of variable quality, and have much less magnetic power compared to OEM

Its worth downloading the 94-96 Parts Manual as it gives part numbers

The '96 has "evolving" connectors. November would be a "late" 96, it is later than my 3

 

Yes, but note the pin numbers on the images are reversed for the two connectors. The pin on the right is still the 5v Supply for both of them. You should be able to tell which one you have by visually comparing yours to the images if you have any doubt.



1996 was a transition year for the XJ. Most parts fit earlier XJs (94, '95). "Late build" begin the change over to parts used on '97 models. You'll see this on lot's of the connectors used.

 

A little bit of knowledge is a dangerous thing. And that, my friend, is why you get to be the resident expert, wear the hat, and wield the clipboard and whistle! :-)

Poorly stated on my part, but my concern was how to rewire the connector correctly since the only version now available is different than the original and the old folks missed that, not so minor, detail that you caught.

I'm guessing from context that a vernier is a brand of micrometer.

Does testing "magnetic strength by lifting spanners" mean suspending a wrench from the magnet on the CPS?

Are we having fun yet?


Thanks
goodyoleboy

 

Yes, that's just AWG showing his age. :}

The aftermarket CPS sensors are questionable, and one of the sure signs of a cheap one is the tip is barely magnetic compared to the OEM one. Don't assume that the new parts are good.

 

Vehicle continues to run fine, but trying to avoid introducing additional variables, I wanted to chase down and rule out the grounding locations before introducing yet another variable with the second replacement CPS. Page 8W-30-14 of the manual shows a reference to sensor ground A-4 at the bottom of the page, but I could find nothing helpful in Ground Distribution 8W-15 or any illustrations of where that or other grounds might be. Attempting to decipher all the cross references between splices and connectors and schematics and diagrams to find the ultimate terminal is apparently beyond my skill set.

I checked and cleaned what appears to be the main ground on the firewall, the ground terminal to which the coil mounts, and the battery terminal, but I could find no others.

The problem does appear heat / temp related as the CEL takes longer to illuminate that it did initially. At first it was within 1/4 mile of start up. Last night it took plus or minus eight miles.

Can you guide me to the ground location(s) for the CPS or should I just press on with the second CPS assuming that replacing the connector will yield success?