1994 Dodge Ram 2500 5.9l Magnum/ATS/AC bought new...they were a lot cheaper then, even though I ranted about the price...
(The actual Question is about half way down marked by a >>>>>>> after all my banter as to how I got to where I an now)

This vehicle has never left me stranded except when I left the lights on, or left the key in the ignition and locked the doors..oops.
Anyway , to make a long story short, I had a critter assisted fire in the Wiring harness connector that took out the PCM, connector, and the first foot of most engine control related wiring.
I completely replaced the wiring harness, and the PCM. The truck would start and run but idled rough and would stall. Apparently over the years the poor PCM was loyally soldiering on and adjusting for wear and tear on sensors and components with out even a single complaint (No Engine Lights).
What I found during my repairs (some may have been caused by the harness fire, some pre-existing)
Crank sensor - bad , would only work every couple days.
Cam Sensor - also intermittent
Park/Neutral switch not always seeing Park although Backup worked fine.
VSS - leaking fluid through the center of the switch.
O2 Sensor heater circuit was open
EGR - clogged
Purge Solenoid - sticking open or closed
IAC motor - sticking
Map sensor - readings way off
Intake Plenum gasket leak - ugh..
Loose timing chain - skipped a tooth
Distributor cap and rotor almost non-existent
Ignition Key switch had bad contacts

Can't believe I wasn't having a problem with this before hand...maybe It was so gradual that I didn't notice? I am NOT a Parts Changer! --really

Well after replacing all the affected wiring and replacing the timing chain and gears (water pump too since I was in there) , inlet plenum gasket, P/N switch, Ignition Key Switch, VSS, O2 sensor, Crank sensor, Cam sensor, Purge solenoid, Map sensor, IAC motor, Distributor cap and rotor, And for good measure, replaced TPS, cleaned all lifters, and cleaned all injectors, and cleaned throttle body and inside of intake kettle body, replaced head gaskets, spark plug wires, and of course all fluids. Found an old "belt squeaking noise" when temp outside was below 45 Degrees...that bothered me for a couple years including a fan clutch replacement that didn't fix the problem...the crankcase breather hose that connects to the back of the air filter hat had a small crack in it that was sucking air - amplified by the huge vacuum in the crankcase due to the internal plenum leak. -replaced the hose. Then replaced ALL hoses in the engine compartment , Thermostat, Intake Air, Temp Gauge, and Coolant Temp Sensors. Also broke oil sending unit when removing the intake manifold ..so there's that.

Not a Parts Changer

What I found out:: Most of the Mainstream parts suppliers out there are selling aftermarket junk that was made in CHYNAH...Original parts are worth the extra cost. Additionally, Most of the online sites don't hammer down far enough to identify your vehicle model or ask for VIN number to verify...like whether it has ATS or Manual Transmission, But they ALL say "Guaranteed to Fit your Vehicle"
For example: Original Crankshaft Sensor 24 years no problems
1st replacement - too short was for manual transmission
2nd replacement - After talking to the service rep to make sure - too short was for manual - and they only stock one part.
3rd replacement - Right length - installed Worked! about 2 hours. internal wire broken at the sensor.
4rth replacement - Right length - we'll see how long this one lasts. When I was running it was fine, and still getting the proper signals.

After getting it all back together over time, (2 year hobby ..I'm pretty busy and have 2 other vehicles)...It ran great except fuel synch, so I ordered a MT2500 off ever reliable Ebay.
The MT2500 seller didn't mention the case broken, or the fast track cartridge shorted out, but everything else works so, ok, for only $200.

Just as I was getting around to adjust fuel synch I was having an issue of misfires so the sync was not steady, then it shut down. ugh...
After a lot of testing found the 8-9 volt out put from the PCM to the Cranks, Cam, and VSS sensors was only putting out 1.7 volts...so no spark, weak signals were enough not to fire off a check engine light or code. Disconnected all sensors, still 1.7, checked wiring ..continuous, and no shorts to ground, checked PCM connector terminals for spread..no problems there.
Bad PCM volts regulator? (insert more Ughh here)
Ordered a new PCM, installed and she saw 8 volts to Crank and 5 volts ref...fired right up.
Went through the MT2500 functional tests that test all the sensors and relays...Injectors, Ignition coil etc everything working, a few misfires but otherwise running, did Sync signal test and it showed off by about 10 degrees. Idling at 889 rpm running pretty good but after giving it gas @ ~ 2000 rpm (and noticing on my scan tool the EGR valve working correclty) the engine would go past idle rpm on the way down (after letting off the gas) past the idle rpm to around 250-300 rpm and stall out. It would restart, but would almost always come back too far down on decel and stall before recovering. Did the Idle air test and it brought the engine down to ~350 rpm and just sat there (so quiet!) ...until it would finally stall. This would eventually lead to flooding the engine with too much gas. I finally got the plug off the idle adjustment screw (the screw showed signs of wear over the years where the throttle bracket was designed to hit it). I threaded the screw in a turn and observed idle speed increase, adjusted it to around 550 rpm.

>>>>>>>>>>>>

Then, after reading numerous internet posts about the need for the PCM to relearn after changes like these I hit one option on the MT2500 that I had been avoiding.
Memory : "Clear ALL Adaptives" ( This is done with the engine not running of course)
Went to restart ---nothing.
The new issue is; I have crank, and cam sensor readings, I have power from ASD to the Ignition coil while cranking, I have injector pulse, But I absolutely get no ignition pulse (grounding) from the PCM - Even when commanding it with my scan tool (which worked fine before).

I hooked up my (bad) PCM and I get ignition pulse and a spark with my scan tool just fine, but remember this bad PCM has a faulty voltage regulator...so no cam/crank/vss signal.from the 8 volt reference supply to power the hall effect coils )

So My Question is: Is there something I turned off or disabled in the programming when I cleared ALL adaptives with my MT2500 scan tool that would prevent a ignition pulse from being set?
This vehicle predates the VIN ID requirement of PCM's, has no Key FOB or security Key device, just an big old metal key. Body Panel crash sensors (one) was not an issue before and no codes or settings for that , and I'm pretty sure this truck does not have the door lock/hood security lockout option..as I would have learned about that the many times I have locked the doors with my only key in the ignition.

MT2500 scan tool : CLEAR MEMORY : ALL ADAPTIVES
Any Ideas? Is there an adaptive needed for spark? Or possibly one disabled that was not used on this year vehicle? (94-95 odb1) I originally did this to "Relearn Crank Sensor" ..which it sees just fine.
BTW both these PCM's auto ID as 1995 PCM's in the scan tool so I have been manually entering VIN which MT2500 reports as the correct vehicle (1994 Dodge Ram 5.9l V8 Magnum MFI with ATS and A/C.), but that to me does not necessarily mean the computer thinks that.

Let me know what you think, in the meantime, I am going to go through the forced flash procedure (which was supposed to do the same thing) which is :
(Warning this was from a Jeep forum and may not work here)

Disconnect Positive Battery lead and touch to ground 30 sec..(which discharges the pcm capacitors and removes the adaptive memory resetting to factory defaults)
Reconnect Battery Cable
Turn Ignition switch to ON (Do Not Start the Engine)
Turn on Headlights
Turn off Headlights
Turn Ignition key off
This should put you in factory default settings...this was reportedly from a Chrysler Engineer and the relearn will take around 50 restarts and around 500 miles to complete.
The re-learn however, does not start until AFTER the vehicle is warmed up to temp And I need it to start First.

If this does not work, before buying another PCM , I will build an external 8/5 voltage regulator and try using the old (bad) PCM that gives spark but improper reference voltages.
And yeah I can here it already...Why don't you just return it...Can't, way beyond the warranty time limit. Best I can do now is use for core charge on an new exchange.

Any thoughts would be appreciated...this truck is practically like new...body was cleaned up and repainted, front and rear suspension was completely replaced with new lift kit and Wheels and Tires, Completely new exhaust (after someone tried to unsuccessfully steal my catalytic converter..but still destroyed everything), renewed interior including Dash and console, floor and headliner. etc.
new radio, speakers, new headlights, taillights, 3rd brake light, and a bunch of LMC Truck decor. It's a keeper, even after all this...not going anywhere. It's still good for another 200,000 miles or so.
(As long as I can survive the CHYNAH parts)...in fact I should probably stock up.. :P
After looking at new truck prices and "quality"...I can dump a lot of money into this ol' Dodge before the purchase price of "new" makes any sense. Besides, looking at the new REBEL...to me it looks like what makes it a "Rebel" is addon decor (mainly plastic) ..any anyone can have a REBEL by visiting and aftermarket add on shop. (Change my Mind!) Pre-Fiat : Collectors Item
Fancy Console Computer? - USELESS , If I wanted that I would just go Electric.






Nothing Special 'cept it's mine. :P

 

Clearing adaptives shouldn't cause any problems. It's essentially the same thing as disconnecting the battery for a while.

Try this, disconnected NEGATIVE terminal from battery, turn on headlights for 30 seconds. Turn off headlights, reconnect battery. Turn ignition key to On, (not start) count to ten. (don't touch anything) THEN start the truck. PCM will take a few to relearn base idle, but, it should happen fairly quickly.

If it still won't start, reverify you are getting spark, and also test for injector pulse.

What brand crank sensor is currently installed?

 

STANDARD MOTOR PRODUCTSPC38{#56027272} from RockAuto ,As previously stated, it's working just fine even though the only thing in the box with it was a label stating "Made in China", I can watch the pulses. If it wasn't I would not be getting injector pulses and a constant ASD supply to the ignition coil during prolonged cranking. I have temporarily removed the fuel pump relay to reduced flooding the cylinders until I get a spark. Again, When the Snap-on Scan tool MT2500 tells the ignition coil to fire with the key on and engine not running, it first closes the asd relay to provide 12 volts to the ignition coil primary and then commands the PCM to send the spark pulse (ground) to the opposite side of the coil...providing a path for current flow , and thereby creating a moving (during the pulse) magnetic field into the secondary of the coil which produces the spark voltage. This test does not require any other component to be working properly, ie crankshaft sensor. It works on the computer with a bad voltage regulator, and doesn't on this one that sees the crank/cam signals, potentials, and pulses at the correct potentials. In addition, the current PCM that was in the engine when it was running 5 minutes before and gave a satisfactory MT2500 functional test for ignition spark not less than 2 minutes before the "Clear all Adaptives" command was given on the MT2500 scanner. The vehicle, which just started before , has no spark now, all others sensors, voltages, pressures , etc are the same. The only two things that changed were the idle adjustment screw - absolutely does not affect the ignition spark function whatsoever, and the "Clear all Adaptives" command. It's Storming here all week and I have not been able to work on it since my last post, but I will let you know what I find out.
I understand that all PCM;s are re-built ,and getting a "new" one is extremely unlikely. Most of the PCM's for sale in the system are rebuilds that didn't work for someone else and may have gone through the cycle several times. It may be safer to get a junkyard PCM if available , but most of those have been stripped long ago. The only thing I can think of is that perhaps ( and why I cleared in the first place) , Is that the factory defaults are so far off from the adaptive settings "learned" for the crank sensor that I am outside some window for the PCM to determine when to send the spark. BUT, that still should not affect the MT2500 scanners ability to command a spark. The Motherboard components that have potentially failed are external to the processor on the motherboards and are not that hard to repair, the jelly digging aside. Electrical I understand. Knowing the actual black box programming code programmed into the computer is something else, but I am sure it's available somewhere.

 

PCM uses cam/crank sensor signals for timing of spark, and injectors. No adaptive learning involved there at all. Since there is no knock sensor on these engines, timing is pretty much fixed according to multi-dimensional tables stored in the programming.

Coil fires when PCM breaks the circuit, and magnetic fields collapse. Put a test light across the coil connector, and see if the PCM really is controlling the circuit.

 

Temp Fix ( I won't run like this, it just allows me to continue tweaking other settings like fuel synch, etc, while I await a new PCM or repair one of these..I certainly have the parts.
Original PCM toasted in wire harness fire in November 2018. Yeah, I know, it's been a while, also why I can't return the PCM's.

This is the Original PCM toasted in the harness fire

This is the 1st replacement of the PCM. Although it appears the refurb was on the voltage regulator..it failed again after 1 hour of running at idle.
Don't know why this image was so small..Anyway this was professionally refurbished. New and lighter color (clearish) potting fluid poured around voltage regulator components.
I lost the 8 Volt supply for the VSS, Cam and Crank sensors. 5v signal was ok. ground was ok.

This is the second replacement PCM. This one lost the ignition pulse signal after about 1 hour of operation. Obvious refurb was for the voltage regulator, and even though it works fine, it can never be repaired again without more damage and extreme effort due to the backyard refurb person using silicone caulk instead of electrical potting jell which is the professional way to do it. The ignition pulse feed comes from a (hidden by jell) chip in the bottom left corner.

Backside of 2nd Replacement. Again more silicone. The silicone is really hard and will break and pull apart connections just trying to remove it. This PCM is not repairable. I will make a point of making comments on youtube videos showing this as a way to repair these.

Temporary Work around:

I took the 1st Replacement PCM with the bad 8v regulator and cut the 8 volt lead from the pcm. I then spliced into the sensor ground to provide a reference ground ( 0 volts) for my external regulator.


I then temp mounted my 2nd Replacement PCM, and fed the Batt +(#3) and Ignition Start (#9) leads with my ASD relay's terminal 86 to provide power only when key-on(run) and Key-start(start) conditions exist. I then ran terminals 11 and 12 to a convenient ground.



I then ran the 8 volt power output of the 2nd PCM ( #7) to feed the Sensors 8 volt lead on the harness, and spliced the sensor reference lead into the existing 0 volt reference (sensor ground) if the harness.


It's Alive! started right up. Now I can work on tuning, fuel synch, etc., and re-learning fuel map adaptives while I decide on whether I should repair 1st Replacement PCM 8 volt (most likely a capacitor..that I have), Or buying yet another refurb and using one of these for core fees....or both.
( I would like to have a good spare..just in case)
The rear end, drive shaft, torque converter, flex plate, all electrical outside the cab (including engine and transmission control wire harnesses, all sensors, solenoids, (including in the transmission). The cabin has been refurbished with new carpets, replacement dash and console trim, new radio and speakers, rocker panels, wheel wells, body repairs and new paint ,etc.. About the only thing not upgraded/replaced in the last 10 years has been the actual engine and transmission themselves. Since I have lived within walking distance from work the vehicle is only just now turning over 100K miles. It's a keeper, at least for now.

Cheers to Rockauto.com and LMCTruck.com for parts and after-market addons. 1994 Dodge Ram 2500 5.9L Magnum V8 w/ 1 inch lift and leveling kit and 32 inch MOTO Metal wheels w/EXO Grappler AW Tires.

edit: Once I replace a blown license plate light bulb and the A/C compressor (hasn't worked in 10 years), this truck will be good for another ~200,000 miles. See you in 2046 !! :P