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P1391 99 auto

4x4JeePmaNthINg

NAXJA Forum User
Location
Colorado
I have a p1391 confirmed code, CEL on
This code was present last summer before my recent engibe swap and it's now present with a different engine.

-Ckps is replacement mopar 1yr ago, yes it was removed before the swap. Ckps backprobed and ohm tested good.
- cmps is Mopar replaced 9 months ago.
- engine fires up right away
- idle feels fine and it drives just fine, no hiccups.

Another member recommended checking side to side play on the dustributor, there's some felt/ heard trying to move it by hand. It doesn't seem much though?


What else should be done for further diagnosis?
 
So I have found two fsm, one for 99:
http://cruiser54.com/?page_id=365
This one seems fairly incomplete it's missing much of what is in the 97s.

And another for a 97: https://xjjeeps.com/#ReferenceDocuments


SO,


-Can anyone tell me WILL the 97 fsm be the same?

-Also is there anything modern/ affordable that can do what a "Drb" scan tool does, or is the stealership mechanic the only person that could have one?

- I have not seen any information that quick checks the cmps sensor itself( yes there are signal volt/continuity test in the fsm for its wiring), but is there no useful ohm quick check for this sensor, the ckps gas an ohm check... Perhaps one of you all know better?
 
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Since that code is for "intermittent" loss I would take a hard look at your wiring for loose/bad connections and for any damage to the wiring itself. Have you seen any indication that it happens at certain temperatures or possibly engine movement?
 
No, it remained an unconfirmed code for a while on the bluedriver, then set off CEL and that stays on always now. It was a cold drive home when the CEL turned on, 5 minutes into driving.
 
No, it remained an unconfirmed code for a while on the bluedriver, then set off CEL and that stays on always now.
Does the ECU still go into closed loop with the light on?
 
Anyone able to explain why fsm is asking to use an analog meter, or osiliscope.
Really trying to be smart at expenses. It's got tools to use, but I don't know what I'm looking for from an analog meter vs digital.

Rcp Phx, you asked about temps. If the CEO is always on, would this matter?
 
No, what I was asking is if you reset the ecu when/what causes it to appear?
 
Anyone able to explain why fsm is asking to use an analog meter, or osiliscope.
Really trying to be smart at expenses. It's got tools to use, but I don't know what I'm looking for from an analog meter vs digital.

Rcp Phx, you asked about temps. If the CEO is always on, would this matter?
What page has the test procedure?

The tricky thing about a random code is that the light will stay on if the problem is not present. I'm not sure about the Chrysler software, but without manually clearing a code, the ECU has to go through a set number of start-run cycles before clearing the code on its own.

Have you cleaned the connectors at the ECU? If you have not touched those, disconnect the battery and git-r-done!
 
What page has the test procedure?

The tricky thing about a random code is that the light will stay on if the problem is not present. I'm not sure about the Chrysler software, but without manually clearing a code, the ECU has to go through a set number of start-run cycles before clearing the code on its own.

Have you cleaned the connectors at the ECU? If you have not touched those, disconnect the battery and git-r-done!

Well that's a bit of a kicker. Here the 99 manual has no diagnosis:
trohHtt.jpg

But the 97 manual does........?
vcoKdKj.jpg


Which is why I was curious if there would be a difference between the years. Even more so, how the heck do you trouble shoot this with no diagnostic procedure in the 99 fsm.

I will try hitting the ecu plugs with cleaner though.
 
https://youtu.be/RUvt_uA09AU
Vid of pulse, cmps sensor tests good.
Tested cmps according to a 97 FSM, mine is 99 so.... turned engine over until the pulse ring was in the sensor, key on power and 5v was supplied. Cranked and checked for 0-5v pulse using a very cheap analog meter. Using electronic cleaner on pcm plugs as hypoid advised, also sprayed cmps plug and harness.
I need to get the CEL cleared after I get a scanner.

Would there be a live feed scanner setting to monitor if this drop a out while driving or would I have to have a meter hooked up?
 
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Is there anything further somebody can it buys for testing the crank position sensor other than ohm tests?

CEL back after reconnecting battery and driving for a bit. Airbag light on as well, I assume unrelated.

does anyone know how much further powertrain Diagnostics manual goes over checking for p1391?
 
No, what I was asking is if you reset the ecu when/what causes it to appear?

What page has the test procedure?

The tricky thing about a random code is that the light will stay on if the problem is not present. I'm not sure about the Chrysler software, but without manually clearing a code, the ECU has to go through a set number of start-run cycles before clearing the code on its own.

Have you cleaned the connectors at the ECU? If you have not touched those, disconnect the battery and git-r-done!

Hypoid this link is for a 97 but I figure pg 986, section 8D-8 might ballpark half the cam/crank sensor test. https://xjjeeps.com/

Why do you want to know if its in closed loop, can you brief me on your question please?

RCP Phx, when pulling +/- to clear the pcm, the CEL comes on with regular driving. Drive easy, drive hard, it doesn't seem to matter.


Ive recently resistance test all wire harness with analog and digital meter.
tZrseL5.jpg

66XSkaM.jpg

I'll be testing pcm for voltage at the signal and 5v supply terminals in just a minute.
And trying this:
"How to test a crank sensor with a voltmeter (All Chrysler models)" on YouTube
https://youtu.be/yp_kK6U8a64
 
sOZyT0D.jpg


- Cmps/ckps 5v supply
. A17/K7
. .09 key off
. 5.19 key oncc

- cmps signal
. A18/K44
. .09 key off
. 5.19 key on

- cmps/ckps ground
. A4/K167
. .0V cranking,key on, key off

-ckps signal
. A8/K24
. 4mv key off, .09 key off
. 1.7mv key on, 5.19V key on
5.26V crank
-ckps 5v supply connected yo harness
. .09V key off
. 5 19 V key on
. 5.26V crank

-ckps ground (2V)
. 0V key off
.016 key on
.180 crank highest

Second row note for signal re test not thinking good probe.

.

.
 
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Hypoid this link is for a 97 but I figure pg 986, section 8D-8 might ballpark half the cam/crank sensor test. https://xjjeeps.com/

Why do you want to know if its in closed loop, can you brief me on your question please?

RCP Phx, when pulling +/- to clear the pcm, the CEL comes on with regular driving. Drive easy, drive hard, it doesn't seem to matter.
I'll try to read through the text tonight.

I am thinking the ECU would go into open loop when the Cam Sensor drops out. I guess the way to test that is have the engine running, with the ECU in closed loop, and unplug the harness to the Cam Sensor.

I did watch the video. When he had his scanner hooked up to show you the square wave, he showed you exactly what the ECU is looking for, to reference the firing order based on the Crank Sensor input. If the Cam Sensor drops out, the ECU will search and approximate the signal based on the other inputs from the Crank Sensor (RPMs) and the MAP (manifold vacuum).
 
Got the scanner back, cleared the code and went for a 35 minute drive. The code showed up as unconfirmed so far no CEL until it confirms it. I'll take a screen shot when it pops up again. Thus far it stays in closed loop, there's a temporary open loop letting off from acceleration.
"Open loop due to driving conditions (bank 1 or both)(e.g. power enrichment, deceleration enleanment, cylinder deactivation)

I assume it's just letting the engine clear power and not adding gas, it was easily replicated on attempts and seemed quite normal.

Unconfirmed p1391, it knows it's there, perhaps it happens a few times before it'll give the CEL.
 
When it sets off the CEL and the timing of it is not the issue/question. It's when you first see the code appear that could give a indication of what changed at that moment.
 
Just started the jeep up before work, I ran inside for two seconds and came back the CEL was on.
9AJJ24B.jpg


The last time it cane on i had started my car after leaving a store, drove 50 ft to a gas pump and it cane on.

And again just now, started up leaving gas station CEL on. It seems lower idle situations it fires on more often, but it's come on while driving before to.
And again just now at work, shut off, turned on right as is started in open loop it looks like CEL fires as quick as it went into closed loop which was pretty much immediately.

????
 
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