TL;DR I need some confidence that my cam/crank shafts are not about to go!!!!

[I disconnect my negative battery cable whenever possible while doing repair work] After replacing my powertrain control module (PCM) last year, I recently in the last few months have got a P0340 check engine light (CEL) and replaced the camshaft position sensor (CPS). On the second start, got a P1391 CEL and replaced the crankshaft position sensor (CKP). Second start again, CEL P1391 but I start smooth and run smooth, so I checked the wire harness for the 5v Supply circuit (k7), sensor ground (k4), CKP signal (k24) & CPS signal (k44). I checked with a voltmeter tone and there is continuity. On the second start, CEL P1391 again. Swapped out both Standard Ignition brand sensors with new sensors. Second start is a CEL P1391. I read a post where someone said to disconnect and ground the positive battery cable to drain capacitor voltage in the PCM, turn the key on, the lights on/off, turn key off. Then drove it 10 miles, but on seconds start is a CEL P1391. Here are my next steps:

1. Disconnect negative cable from battery.
2. Remove radiator shroud.
3. Rotate engine until timing mark on crankshaft damper aligns with TDC mark on timing chain cover (Fig. 61) (#1 cylinder exhaust stroke) and the camshaft sprocket "V8" marks are at the 12 o'clock position (Fig. 62).
4. Reconnect Negative Cable to battery.
5. Start the engine, drive for ten miles, stop and restart engine.

After doing this, I am suspecting one of the following:

1. Broken/Damaged wiring on one of the sensors
   1. Possible that you cannot see or determine with voltmeter tone
2. Damage to my Camshaft or Crankshaft tone wheel pulse ring
   1. I see this as unlikely since there is no issue with performance
3. Defective sensors
   1. I am not going to say I can explain why OEM parts and AfMkt Parts built to the same specs are different, but many people are telling me to go OEM

The field manual provided by the manufacturer (alldata DIY) lists these possible causes:

• Damaged tone wheel/flex plate
• Damaged tone wheel/pulse ring
• Irregular lab scope pattern of cmp signal
• Wiring harness intermittent defect
• Intermittent ckp signal loss when wiring is wiggled
• Irregular lab scope pattern of ckp signal
• Intermittent cmp signal loss when wiring is wiggled
• Sensor connector/wiring defective
• Cmp sensor defective
• Ckp sensor defective
• Cmp sensor out of sync

I did fear damaged crank/cam shafts, a cracked exhaust valve, blown cylinder heads or something major

Are there ANY possible other reasons/methods/solutions out there that a B-level do-it-yourselfer like myself can check off before I throw my hands up and put faith in my local dealer mechanic?

 

Nobody replied so I just kept on keepin' on. I hope someone will reply with some good ideas so I don't have to give up on this old truck!

I looked up the code again in the FSM to find out more information about P1391 (symptom) possible prognoses

1. Damaged CMP signal/power/ground wire damage
   1. Solution: Replace 18ga signal/supply/ground wires, conduit, ignition terminal pins, PCM/ECM terminal pins, sensor connector/housing [in the process of doing this to isolate the issue]
2. Bad "NATIONAL BRAND" Sensors
   1. Solution: replace sensors with MOPAR brand
3. CMP and CKP sensors out of sync
   1. Solution: Set motor to TDC, clear codes and start engine twice. repeat 10 times or until successful.
4. Loosened/Damaged/Defective Cam/Crank shaft tone wheels
   1. Solution: replace tone/pulse ring on crank/cam shaft
   2. might as well just replace cam and crank shafts at this point which means a rebuild would be cheaper but luckily this is a low-probability scenario

Here is a list of tools/supplies I think I need to repair the wires & sensors:

1. Miller Special Tool 6934 $12.50 each from ebay
   1. This is the only tool that you can use to pop out the terminal pins that go into the PCM Connector
2. OTC brand 6pc terminal release tool set p/n 4461 that you can buy at NAPA
   1. you can use tool C in this pack to remove the sensor-side terminal from their respective connectors
3. proper color wires
   1. good luck on finding anything close to the correct color codes but they say you can just put orange in there and it will tell someone you repaired it recently
   2. You need some 18ga quick-splices for the supply and ground cables because the CKP & CPS circuits use the same PCM connector ports
4. Multi Purpose Terminal Connectors for the sensor-side connector
   1. This part was my downfall because it was listed as the wire harness for the CMP but was a big failure after I discovered all the details here
5. Delphi micro pack 100W Terminal 18ga
   1. these are the pins that the wires have to plug into before they are plugged into the 32-way Thomas and Betts connector that plugs into the PCM
   2. delphi p/n 12084912 terminals on
      amazon
      amazon
6. MOPAR Parts for sensors
   1. Camshaft Position Sensor $48.85
   2. Crankshaft Position Sensor $79.95
7. If the WIre, Sensor and TDC plans don't work, I have no choice but to take it to a Jeep dealer to have them troubleshoot/lab scope the issue using their DRB

ALSO NOTE: the exhaust valve, cylinder heads or some other major deal is not a factor here.

 

I have found out the following:

1. The national brand multi-purpose connectors work fine but only come with one color-code of wire so you have to mark the wires going into the connector for future trouble shooting
2. The Delphi Metri-pack 280 connectors are too big to replace one wire at a time, and besides that, the 5V supply and Sensor Ground circuits service both the CPS and CKP sensors
3. I tried to build a partial harness with a contiguous data circuit for each of the sensor and a supply & ground circuit that splices into each sensor.
   1. Main branch: 6 foot power, supply and data circuit to service between the CPS and the PCM
   2. Secondary branch: comes off the main branch about 3 foot down and branches into a power & ground thats about 18 inches long (contiguous data circuit 54inches long from sensor to PCM
   3. I jacketed it with red-colored conduit so I could tell which one was the repair line
4. BUT I HAVE TO BASICALLY GO BACK TO DRAWING BOARD BECAUSE THERE ARE OTHER SENSORS SUPPLIED/GOUNDED BY THE SAME CIRCUIT
   1. The cps/ckp circuit labeled as k7/k4 on the diagram respectively service other sensors and you cannot just replace that line to the sensors.
      1. Splice 107 leads to the Throttle Position Sensor (TPS) ground circuit k4
         1. it also grounds circuit k4 on the Engine Oil Pressure Sensor, Manifold Absolute Pressure Ground, Engine Coolant Temp Sensor, Intake Air Temp Sensor
      2. Splice 112 leads to the TPS ground circuit k4
         1. It also grounds the Battery Temperature Sensor, Oxygen Sensor 1/1 Upstream, Oxygen Sensor 1/2 Downstream
      3. Splice 105 leads to the TPS 5V supply circuit k7
5. The wire replacement decision tree has grown an awkward branch. I have to decide between the following:
   1. Jumper-Splice into the wires a few inches back and replace just the connector on both ckp and cps wire harness (Leaving about 6 foot of potentially shorted/faulted wires for some shop guy to repair hopefully)
      1. I could potentially still run a contiguous signal wire though.
   2. Replacing the entire engine sensor harness (which could be difficult since there is not one readily available for under $800 on the market and missing just one branch could throw a new code, not to mention the potential for a misplace/misfit part is always there)
   3. Replacing the Tone wheels (WAY TOO EXPENSIVE, MAY BE UNNECESSARY AND A BIT RISKY SINCE I AM STILL T/S-$1200-$3000)
   4. Taking it into a shop to get it on a lab scope for them to inspect the wiring (Which I know they will just suggest replacing the wire anyways-$500)

(EDIT) After doing some more testing and research in the FSM on alldatadiy, the following conclusions are relevant:

1. Sensor Ground circuit k4 Splices (S107 & S112) are the points in question
   1. The TPS passes through S107, and since it has no code, that length of wire must be good
   2. The MAP, IATS, Oil Press sensors pass through S112 with no code, so the wire is good up to that point
2. 5v Supply circuit k7 Splice (S105) is a point in question
   1. The MAP & TPS pass through S105 with no code so the wire is good up to that point
3. The connectors are points in question
   1. each of these points are being questioned for intermittent electrical problems
      1. But since there is no significant resistance, its unlikely
4. Most intermittent electrical problems are caused by faulty electrical connections or wiring. It is also possible for a sticking component or relay to cause a problem. Before condemning a component or wiring assembly check the following items.
   1. Connectors are fully seated
   2. Spread terminals, or terminal push out
   3. Terminals in the wiring assembly are fully seated into the connector/component and locked in position
   4. Dirt or corrosion on the terminals. Any amount of corrosion or dirt could cause an intermittent problem
   5. Damaged connector/component casing exposing the item to dirt and moisture
   6. Wire insulation that has rubbed through causing a short to ground
   7. Some or all of the wiring strands broken inside of the insulation covering.
   8. Wiring broken inside of the insulation
5. All but the underlined of these "intermittent issues" can be tested with an Ohm Meter
   1. Autozone tells me that wire resistance is a max of 1.5 Ohms (but I set my standard to 1 ohm with all wires < 0.4 ohms)
   2. Since there are no changes in ohms when wiggling various parts of the harness, the circuit must be fine
6. AFTER ALL OF THIS CONSIDERATION, I feel the wires and connectors are perfectly fine
   1. I have ordered MOPAR sensors to replace the NATIONAL brand ones based on
      amazon
      amazon
      reviews
   2. I also need to make sure I get that CKP and CSP hole that the sensors plug into cleaned out really good.

 

To fully follow up, the answer was clearly using MOPAR brand sensors. Once replaced, I have drove ~1k miles without another code. SOLVED

 

That's a completely absurd rabbit hole you went down! Mopar demands quality from all their suppliers with in-house inspections at point of assembly. A lot of their parts are now made in Mexico. I questioned their quality but was informed by a man who was an inspector in a Mexican factory how rigid Mopar is on their standards. He tells me their crank sensors use a neodymium magnet and most others don't. All I can tell you for sure is the Mopar crank sensor I replaced mine with would stick to a screwdriver and the old one didn't. The strength of the magnetic field is important in this instance. Also mounting distance from the tone wheel is critical, especially with the crank sensor because of the high speed at which the flexplate is rotating.

Also, a tone on a meter will only show continuity but not resistance. Loss of voltage in a 5v signal due to resistance can skew results. It's amazing how far you went without scoping the signals. If a 5v signal when grounded remains at 2v, it can show a fault code for that sensor.

Personally, I'm not buying anything newer that this model because of the complexity of the newer systems. Case in point, the rear window wiper motor has a logic module in it, only because the delay function changes speed to compensate for vehicle speed! Why is that needed? Most newer cars have a TIPM (Totally Integrated Power Module) instead of the PDC and has digital circuit boards and hard wired relays in it . To replace that unit costs around $600 just for the part!

Enough rambling. I'm happy you got it fixed because to diagnose that thing via a keyboard wasn't going to work and may have sent you in the wrong direction. I can understand your paranoia about the 4.7 after all the horror stories floating around. I'm still running a 2000 XJ with the 0331 head after having the one on my WJ crack.