DoJo

[QUOTE=CCKen;2124438]The TCM is located under the dash by the steering column.



P1391 is:

CMP=Camshaft Position Sensor, CKP=Crankshaft Position Sensor

P1391-INTERMITTENT LOSS OF CMP OR CKP

Possible Causes

CMP SENSOR OUT OF SYNC
DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)
DAMAGED TONE WHEEL/PULSE RING (CAMSHAFT)
INTERMITTENT CKP SIGNAL LOSS WHEN WIRING IS WIGGLED
WIRING HARNESS INTERMITTENT
SENSOR CONNECTOR/WIRING
SENSOR CONNECTOR/WIRING
CAMSHAFT POSITION SENSOR
CKP SENSOR CONNECTOR/WIRING
CRANKSHAFT POSITION SENSOR

Note the intermittant wiring harness and the signal loss when the wiring is wiggled. The XJ wiring is subject to chaffing, especially in the engine bay. Wiggling wiring harnesses and visual inspection of wiring and connectors are routine diagnostics for XJ's. You may want to give this a try.
TEST

Thanks for the diagram - that would have been the last place I would look for it.
I have one more piece of info - fuse 11 blows when I put it into reverse and put a load on it. ie: foot on the brake and try to go in reverse.
I hope this sheds a little light on it...

DoJo

CCKen

"I have one more piece of info - fuse 11 blows when I put it into reverse and put a load on it. ie: foot on the brake and try to go in reverse.
I hope this sheds a little light on it..."

Does this mean that if you put in reverse but don't ride the brake it doesn't blow the fuse?

DoJo

The fuse blows either way, put it into reverse and step on the gas and the fuse will blow.
If I do not press on the gas and let the idle move it it's OK.
Man I hate to be a PITA about this.

DoJo

CCKen

Will the fuse blow if the engine is not running, the key is in the RUN (ON) position, the transmission is shifted to reverse, and the gas pedal is depressed? I assume you've been experiencing the fuse blowing with the engine running, and it quits because the FP and ASD relay coils lose their power.

If you have an O'reilly auto parts near you they sell those blow and glow type mini fuses (light up when blown). You could put one of these in the fuse holder and have a helper watch the fuse closely as you try to simulate the condition under which it blows. Key in Run/engine off, shift to reverse and see if it blows. While in reverse, depress the gas pedal and see if it blows. Repeat with the engine running if neccessary.

The only association the gas pedal has with the transmission is through the TPS to the TCM. The same voltage signal that is generated by the TPS and sent to the PCM is also sent to the TCM. I have no idea what P1391 would have to do with your fuse problem except you may have more than one problem, or the wiring in your engine bay is dicked up (which you haven't said you checked) and is also affecting the CMP or CKP. Unless, of course, it's the "P" word (PCM).

DoJo

I appreciate everyone's help and advice.

I did check the wiring and everything seemed OK - checked the O2 sensor and nothing is rubbing or chaffed.
This problem is intermittent so I am still able to drive the Jeep.
I'll dig further into this and will keep everyone posted.

Thanks again!

DoJo

SiouxSays

I have a 1995 Jeep Cherokee Country, and I am the 2nd owner (previous owners were my parents).

The Jeep sat for 6 months before I acquired it.

It is doing the exact same thing that DOJO described.

When running and placed in reverse, when there is a "load" on the engine (giving it gas) the fuse in the passenger footwell that controls the "run/start & ignition" will blow. It's a 20A fuse and is 4th one from the bottom on the side of the fuse box toward the engine.

I have gone through probably 100 fuses in the past 8 months because of this issue.

It used to NOT do it while simply idling backward in reverse, but it will now do it more frequently. Also, it does not do it ALL the time (more so now than before, also). And it is now blowing that fuse infrequently when in drive and moving forward (terrain type doesn't seem to make a difference).

An odd note: When the fuse is replaced and the engine restarted, it will sometimes restart at a high idle (2500 RPM), rather than normal low idle (around 800 RPM). When it does that, every time I put it in reverse the fuse will blow due to the load on the engine.

Any answers please?

DFlintstone

Welcome Soux! Three things. In your shoes I'd start a new thread (since it's a 95). Link to this one maybe. Fill out your info so people won't need to look to see what you have, and third, get your codes. They will do it free at the auto parts unless you are in CA or HW...(we don't know where you are).

The "key trick" may well work on your 95> There is a code key in "info threads" at the top of this forum.

"OBD1 Models: 1991-1995
1) Start engine (if possible). Move transmission shift lever
through all positions, ending in Park. Turn A/C switch on and then off
(if equipped).
2) Turn engine off. Without starting engine again, turn
ignition on, off, on, off and on within 5 seconds. Record 2-digit
fault codes as displayed by flashing MIL.
3) For example, fault code 23 is displayed as flash, flash,
4-second pause, flash, flash, flash. After a slightly longer pause,
other codes stored are displayed in numerical order. When MIL begins
to flash fault codes, it cannot be stopped. Start over if count is
lost. Code 55 indicates end of fault code display.

CCKen

It's only been four years waiting for a follow up. I guess I'll go back to sleep now.

CCKen

Time to eyeball the wiring in the engine bay.

Closely examine the wiring harness (loom) at the end of the fuel rail for chafing through the loom and into the wiring. This is a common problem area.

Next, examine the wiring coming off the three connectors at the transmission dipstick tube for chafing. It may be difficult to get a good look at the wiring loom but you need to do this.

These are all items associated with movement of the engine that people have found to be the fault.

Check all wiring harnesses and connectors in the engine bay while you're at it.

DFlintstone

Is it 2016 already? I guess both me and to PO took a nap....

CCKen

LOL

I guess I was napping all along.

ChitownCraig

I'll restart this thread since I've been having a similar problem and you guys have a lot of knowledge. My run/start fuse is blowing as well but it only does it sometimes. I just bought the Jeep and I drove it for a week and it drove fine. I changed the plugs, cap, rotor, and wires. I drove it around and then from a stop I accelerated hard and it died. Changed the fuse and it drove fine. After that when it does happen, I'm stopped and I push the accelerator to go and it dies immediately.

thegee

I had an issue like this. Fuse 11 blowed ( down the passenger side) when in reverse. I had a grounding with my reverse lights. I did cut the dark Brown and Green wire going out from the NSS and no more more problems 😄
Then unscrewed the interior rear right panel in the car box where you have all grounding connections in order to found that i had a bad 101 grounding
If it cab help 😄

Ladarius

Mine has blown three times but only on a trail. I drive it every day, no worries. The first time I had been in the woods all day long and on the way out on flat ground it randomly blew. Then 10 feet into a trail a few weeks later it blew. Then last weekend I made it in the entrance of a trail and it blew half way up a relatively steep hill. ugh

ChitownCraig

I thought we had the issue fixed with changing that coil out but it doesn't look that way. Looks like it has something to do with temp and throttle position. The Jeep now will die randomly after I press the gas pedal for about a second. I will be stopped at a light or stop sign then press the gas and the jeep will go and then blow the fuse. This is the only time it happens. I've had the Jeep running and get up to full temp in park and it doesn't die.