Hi everyone!
(Transmission experts)
Preamble, I have something similar embedded in a separate thread here regarding the cruise control. However, I feel this warrants its own thread for the specific issue and details around it. I am posting this here to see if anyone in this group has had or seen similar and really truly understands it.

I have an interesting (to me) thing going on with my old Dodge. The problem appears to be happening with Dodge's of various years, it is not only my truck. I have been doing online searching but have not yet seen anything as specific to what I will describe. I am a technical guy who goes to the root and is not satisfied with just swapping parts. I would really like to understand, in detail, how this can occur electrically - electronically. A wiring diagram and control flow of this circuit would be helpful. The description of the scenario is a bit long so I am going to ask the questions at the start, then as you read the description it will reveal why I am asking and may reveal plausible answers.

Questions:
Q1: Where exactly is the neutral switch that the PCM uses? That specific piece of hardware that is responsible for the neutral signal going into the PCM. There may be one in the solenoid pack and slide plate on the valve body. Is there any secondary such as the steering column. Which harness and which to probe to fault check it?
Q2: What is the fix to the switch? There is alot of chatter about replacing the whole solenoid pack. There is also a solenoid rebuild kit. The transmission is working perfectly fine, only the neutral switch seems finicky - but where is it.
Q3: What are the specific functional differences between the black solenoid pack and the white solenoid pack? I do not yet know which one I have, as I have not gone under the truck yet. Too cold and too much snow.
Q4: Any other thoughts or suggestions to fill out the discussion.

OK, that out of the way here is the scenario and observations I am wanting to get to the bottom of.

**********
I have an '04 Ram, 5.7, 1500. Occasionally have cruise control function problems. It is intermittent. Many times it works perfectly fine (80%). Sometimes it isn't (20%). Damn you Pareto! It has not been consistent so, UNTIL NOW, it has been impossible to say it is this or that. The symptom will be consistent within that trip or that key cycle, and may change the next time you start the truck. Ie not always the same. Observed symptoms:

1. - cruise sets and works perfectly fine below a certain speed. When road conditions clear and increase speed set point all is good up to a certain speed range. Then the cruise it turns itself off, and it cannot be turned back on until speed is reduced below the range. On my truck it varies in the range of 118 - 124 kph. The cruise light on the dash goes off, cannot be turned on.
2. - cruise light is on in dash but cruise cannot be set at all. It does not engage and hold speed at all. Stop the truck and go again and it works fine.
3. - no problems whatsoever for most of the trip, cruise turns itself off and then cannot be turned on again or it turns on but does not engage when speed set button pushed.

Logic says that causes of problems with the cruise control function can be; electronic/digital in the PCM, electric in the wiring or sensors, and perhaps vacuum line to the cruise solenoid.

I replaced the vacuum line and the PCV awhile ago. The cruise control problem disappeared for quite awhile. So that was a fix? Nope. I just haven't used the truck on the highway much since. The problem still occurs and is inconsistent. Sometimes it works, sometimes it doesn't.

Recent observations, new development !

This is a multipurpose vehicle for me. Sometimes it is a pleasure driver, sometimes a daily driver, sometimes a workhorse hauling loads, sometimes a heavy towing rig. I have a diablo sport inTune programmer that I use on this truck to change the program depending on what is going on. The current program is basic aggressive roundabout driving. However, I have some teenage drivers who take this truck. To protect the old truck from their antics I have changed a couple parameters in the program. Specifically the rev limits. There are two rev limit options in the diablo. One for when in park/neutral and one for when in drive. I have the neutral rev limit set at 3800, so the teen does not over rev in the parking lot and blow rods out of the side of the block while making catchy look-at-me noise for their friends. The drive rev limit I have set at 5250, again to keep them from popping parts high revving under full throttle when wot is not necessary. Remember these numbers, they are important for what's next.

Just recently was an interesting and enlightening experience. I was on a long 5 hours trip. I pulled out to make a pass and gunned the Hemi. It rumbled and ramped up with authority exactly as expected until it hit 3800-4000 rpm then abruptly cut back. Out on the highway. "What the heck!" said to me. Tried again, it did it again. Here is where the different rev limits programmed comes into play. I am bombing down the highway at 100kph and pull out to make a pass. I gun the engine and it caps at 4000 rpm. All during this trip for 3 hours prior the cruise control can be turned on, light on, but it will not engage at all when set. Hmmmmm. ..... I was in the middle of nowhere a hundred of kms from civilization, there is no way I was stopping and end up being stranded at a turnout. I carry on for another luxurious and uneventful hour of driving while thinking over the truck's systems. I stop at a convenience store and turn off the truck. I hook up the Diablo and verify my thinking to the set points that in the program. I did not reprogram, just checked the settings. I restart the truck and carry-on with the drive. Get onto the highway and gun it. Zooom! ramps to 5200 easy and off we go rip roaring tearing up the asphalt. Since the stop, the cruise control worked fine and rpm limits were fine entire rest of the trip home.

*** --> Here is where all of that is leading to ..... somewhere somehow even though the truck is driving fine down the road and the gear shifter is in drive, perhaps there is a flaky signal telling the PCM that the transmission is in NEUTRAL. (?). There is NO other explanation for why the rpm capped at 4000 earlier in the drive. It also makes perfect sense that the truck would not allow cruise control when there is a signal telling it that the truck is in neutral. Perhaps this is also an explanation for what is happening a those times when the cruise control is dropping off at a certain speed. It could be that speed coincides with a perfect vibration level that is affecting the contacts of the shift position sensor and bounces it between Drive and Neutral? Or maybe it is a combination of speed sensors and neutral/drive switch.

Based on this experience and observation, My next steps in figuring out this cruise control issue is to get to the bottom of the what where and how does the PCM get the signal of what position the gear shifter is in and how that is processed with respect to the cruise control. Try to determine a cause for how that could be intermittent. Specifically the points between D and N and whatever sensors are responsible for that. At this point it appears that sometimes that signal is not indicating properly or changes on the go which affects the function of the cruise control program. (and maybe other stuff I haven't discovered yet).
Finding physically where on this truck these devices are is a new one to me so if someone can help point where to start looking and troubleshooting that circuit, I just may get this cruise control thing finally and completely resolved.

The truck otherwise runs and performs stellar. There are no other transmission-engine issues other than this intermittent cruise control problem which I think I have narrowed down to a flaky shift position circuit. An afterthought, as I have 4wd this could be a significant problem if I (or the young drivers) had a brain fart and switched to 4Lo on the highway = Ka-BOOM!

Sorry for the long description. I hope it was easy to follow. For me and others this may point to the cruise control problem being something other than the vacuum circuit or the cruise control solenoid or PCM. I would have never thought of this neutral signal had I not programmed the separate rev limits.

If my logic and my troubleshooting proves out, perhaps this should put put up somewhere as a one of those "sticky" posts for quick answers to a baffling problem about cruise control that sometimes works and sometimes not.

Thinking about the many many other posts about 4wd switching problems, limp mode problems, delayed engagement from park to driving problems .... this may be the culprit, the root cause of all of those.

Looking forward to some revealing discussion and direction on this.

Hope that helps!
FaceDeAce










2004 Ram 1500 4x4 auto.

 

Can you do data logging? I would be tempted to set up for it, hit the highway, and see what shakes out. If the cruise works, see what gear the PCM thinks the trans is in, same for if it doesn't work..... an intermittent signal there could certainly cause some interesting symptoms...... As to where the switch is? No idea.

 

Unfortunately I do not have data logger equipment that would capture that specific signal. If such a tool even exists it may not be readily available? Who would have such a thing?

I got as far as determined that at least one of the shift position sensor device set is a group of pins that extends off the end of the shift solenoid block in the transmission. The web info I dug up is quite specific about the shifter plate change that has to go with a solenoid pack change between the black connector and white connector versions of the pack. ... Which leads me to suspecting that is a good place to look and give the wiggle tests. Though I will not be taking this one apart to go that deep into the transmission until warm weather, June at earliest.

Not convinced to replace the solenoid pack if all this is is a worn pin or a sticky pin that slides on that plate. Could easily be a 0$ fix.

Just a couple of short reads done so far on this:

https://gearsmagazine.com/magazine/d...ate-confusion/
http://d2q1ebiag300ih.cloudfront.net...f?v=1487624594

.

 

From what I am seeing, P/N sense is indeed part of the solenoid pack, and there appears to be only one. Connector 3, pin 21. Now, what kind of signal it is sending, I don't know......

 

OK, thanks for checking. If there is only one source of the signal, therefore I will focus my attentions on pulling the transmission solenoid plug end that is up under the hood somewhere and using test leads there while the boy sits in the truck and moves the shifter. Eventually, I foresee the solenoid pack will come out and come apart for inspection and service adjustment / cleaning or replacement. Depends on what is seen.