Crabbi

I have done the PCM reset multiple times, we did run diag on the o2 sensors and had normal operating volts and they fluxuated with the enging open loop closed loop function, like i said though this thing runs, its popping through snorkle but running, when it first went back together it ran flawless at cold start, its slowly progessing and no codes, If it skipped a tooth it should show me some code for timing or lean or misfire, this jeep will sit there popping through the carb with no check engine light
I am down to ohm testing wires going from the cam sensor to the pcm plugs, i can ohm the signal wire, tan or yellow, its ok, i get a 5 volt reference on the orange wire, the remaining wire traces back to pin 4 on the pcm harness, i ohmed it but im questioning what i should see as the path it takes goes through a couple other connections. any ideas,

Pin 4 is the ground shared by the crank sensor and the cam sensor, I aam trying to ohm from the cam sensor wire to pin 4 but im getting high resistance, is it because its a shared ground and are there other things on that ground or is it because i have a short in that wire causing all of this? can i jump the wire at the harness plug and go directly to the cam sensor? that might leave the crank sensor with a fault except on the scanner the crank sensor shows it synced, thoughts?

Dave51

IIMW I'd expose the wiring in the harness. If there's a short, multiple wires could be involved.

Crabbi

I may try that tomorrow, the new PCM comes in Friday, i would like to make sure i dont have a ground issue thhat could cause the new PCM to fry or not resolve the issue, i hate throwing parts at something, this thing has put me through the ringer,
any idea what kind of ohms i should be seeing from pin 4 at the harness to the cam sensor?

Dave51

Can't help there. By the schematic it should only be ~1.0 Ω. You got 2 splices and lot of other stuff near high heat on that circuit. I'd measure it myself but it's late, looks like rain, back hurts, cat needs to be fed, gotta watch NCIS...

Crabbi

im thinking of bypassing the whole thing, run a twisted set from PCM to cam and cranks sensor, just bypass all of it, if that works then i know i need to repair or replace that whole harness, if its only those wires on that ground in the pcm and i just bypass it all then that should fix it,
I will keep looking for how many ohms i should see on that wire, it should be listed somewhere, 1 would make sense, bouncing around at 90 does not, unless it has multiple switchs etc on that same wire, the diagram page 672 just shows the cam and crank on that ground in the pcm, bypassing the whole thing makes sense dont it?

Dave51

I'm not understanding what you're saying above.

When I posted



You said

So if it looked like that, it CAN'T be CPS/CKS.

IDK which diagram you're referring to, but Pin 4 has a ton of stuff on it




so again IMO you shouldn't be doing workarounds because even if the bypass does work you still got something in there that could be affecting other sensors.

See if there are any volts on Pin 4.

Crabbi

thank you again for your help, and you wonder why i am in here trying to get help?, lol this does not make sense unless its the PCM or a wiring short, we watched the signals on all sensors we could, we watched the o2 sensors come out of loop we tested the coolant temp sensor, we tested the map sensor the injector test was perfect, i am trying to verify none of the 3 wires on the cam sensor have a short, during the first time i did a back probe and found in spec, during a just regular ohms test of each wire back to the pcm is where im finding this, the yellow or tan wire is supposed to be a ground at pin 4, when i try and ohm the harness from the yellow/tan wire back to pin 4 on the plug i get 90 ohms, thats a failure in any other ohm test unless its supposed to have higher resistance due to what i dont know
but thats why i am asking. my jeep is page 672 for just the cam sensor crank sensor, california emissions
unless its PCM which i wont know until friday because my 2000 cherokee has california emissions and its a one year PCM, if i put it in and it fries due to a short thats not going to be good,
there should be a spec if its supposed to have resistance,
im trying to ohm just that ground wire on the cam sensor back to the PCM harness plug, at least that would show me i dont have a short in that ground wire and im not risking my new PCM, i will check for power at pin 4, i have been ohm testing with the PCM pluh on the harness unplugged, i will post back in here after im done, heading out now, i should not have any power on a ground wire unless its backfeeding through it, which is again why i am thinking of bypasing it, but no codes and no errors on scanner other than cam sensor saying sync then lost syn then sync then lost sync repeatedly

Dave51

A "short" per se would have a Ω closer to 0.0. High resistance is broken wires and bad connections.

Again, see if Pin 4 has any volts.

Crabbi

i plugged the harness back in and just ran voltage test again i checked cam sensor plug at sensor with key on and i have 5v at both the orange wire and the yellow/tan wire, the center wire or black/brown has nothing, i dont think i should have power on both wires considering the one is called a ground in the wiring diagram, unless im missing something.
this may be why i cannot ohm out the other wire to pin 4 on the ground side, something is powering it, reading that the signal wire has an on and off voltage i guess i could have 5v there hit and miss due to signal, but the wiring diagram and the harness dont match the testing information i have seen on that plug, most calling the tan wire a signal wire while diagram calls it ground wire?

note: when trying to ohm the tan/yellow wire back to pin 4 with harness unplugged i get anywhere from 190ohms and lower and it will cycle up and down on the volt meter, leading me to believe bad connection, thats why i was asking about bypassing the ground at the cam sensor except it would leave the short alive and connected to whatever else is on that exact wire in the harness, if its just the crank and cam sensor i could run a patch harness and cut that ground system out or find it and fix it, or replace the harness, this being a one year PCM and california emissions i may have a problem finding a new harness
it almost certainly is the PCM or timing chain, unless i have a short, i have a replacement PCM coming and i am more than willing to put a timing chain in it, but i really dont like throwing parts at it, i already tried that route with the crank and cam sensor, then i replaced the map just because its part of the open closed loop operation , it tested good, i spun the crank while watching the cam sensor drive assembly and it moves pretty quick but i think it still could cause a lost sync in sync kind of situation if the timing is jumping all over due to lose chain

Crabbi

New PCM came in this morning, installed it starts right up then dies, i pulled codes just for the heck of it got a p1686 no skim bus messages,it wont stay running now, it ran before horribly but it ran, i wonder if i need to scope the cam sync assembly to get it back to zero, or is the bus message saying my new pcm is bad also lol, thats what it looks like, and it was a used PCM

Dave51

Nope that's a whole new problem. The "new" PCM thinks you're a car thief and has shut everything down. IDK how to fix that w/o $$$$.

Post a new thread and see if a SKIMMER has a cheap solution.

Crabbi

i agree thats the theft system shutting it down, needs to be programmed to this jeep, but popping through intake was still there,
I rechecked the timing chain, i get 8 degrees of play using cranks shaft tdc as mark, when rotating i get 8 degrees before cam sensor center piece starts to move, do you know the spec? could it have to much play not allowing the cam sensor to sync?
I have yet to see a spec for timing chain play,

i have no problem spending money on it, my concern is so far a 16k scanner and replacing parts based on that have done nothing but cost me about 700 bucks in replacing parts, based off of cam not being in sync and it going into closed loop and clearly studdering and skipping with no codes, like a jumped chain, but top dead center on crank and checking orientation of the sensor makes it look like it did not jump

Dave51

Post 2 graphs:

The CPS/CKS (I made that with my $100 o-scope so I'm sure you can do it with a $16,000 scope);

The cranking volts/spark generation.

Crabbi

Its not my scanner, my buddy owns a shop and hes trying to help me, he just went in the hospital for BP issue, he says he will probly stop by again Saturday, ill ask him to pull all the information he saved, he took it home to print it and go over it,
I pulled the timing chain cover looking for slack in the chain, its close to 3/4 of a inch, i bought a new one anyway so ill just put it in to save myself the worry, only took an hour or so to get to it,
Ill see if he can email it to me in a pdf or something, im sure he can,

i cant say for sure the timing chain isnt going to help but i dont think its the problem, on his scanner when looking through everything, the only thing noted was the cam sync going off and on, the crank synced and showed no problems, the cam simply will not sync, i did check endplay in the cam, its not that,
im gonna offer a reward if anyone gets this resolved, this isnt a hobby, my sister broke down, shes not broke but this is her car, im paying for all this to help her get it back going, she goes for surgery on her shoulder this month then will be out for 6 to 8 months, i gotta get this thing fixed, she originally dropped a lifter, which led to the valve job and then this started, Im disabled thats why im in here all day asking questions, i used to do this kind of stuff my whole life, i was GM certified, Mack and Volvo, Mitsu, Hino, but i lost all that after my accident, so im retired so to speak, Im not kidding about the reward, i got a 100 bucks i can send through paypal or something if i can get this dang thing fixed. i spent so much on it now it just doesnt matter anymore,

5-Speed

I would pop the trans inspection cover and check the flexplate for anything odd, like being warped. If it's warped enough, you should be able to see it while running.