milradioman

Mike, When my blue wire shorted to ground, the PCM apparently shut that line down, preventing damage, I had purchase a replacement PCM thinking that was the problem. My engine dipstick tube would rub on the wire harness every time the engine torqued, from starting or hard acceleration. Eventually the insulation rubbed through, but only shorted when I started the engine, talk about a nightmare to track down; When the engine was off, the blue wire not shorted, start engine and no short, but no output. Since I started and stopped the engine multiple times, my best guess is each time the wire shorted, the PCM shut the output off to protect the circuit. Although in my case the wire was grounded momentarily, a constant short to ground may have a different result. I have no problem performing the modification, better safe than sorry, and I will add it to my list of must do. I wanted to share my experience that is similar to yours. Nice clean job on the mod. Brian

"You shorten the charge wire from the alternator and run it to the passenger battery. " Well, that makes too much sense, I was hung up on keeping the alternator positive connected to the "main"/drivers side battery, as long as the battery connections are clean and tight it shouldn't make any difference which battery. I talked to a mechanic near me about my mods, he was told the mod only involved moving the field wire from the PCM out of it's wire harness and route it another direction, like on the other side of the air filter. Apparently it is picking up interference also, I have not looked at the wiring diagram yet to see what else is run with it.

I was having a horrible problem with my transmission down shifting, it got worse over time, I rebuilt the alternator, that helped for a while. I finally performed this ground mod, and all the problems I was having stopped! I did not measured the voltage ripple before and after the mod like I should have, but I do have a good indication that it really made a difference. I did not remove any of the brackets to get to the wire harness, though it would make it easier to work on. One question I don't see answered yet; where did you route the alternator positive wire to get it away from the wire harness? I used new split loom for the main cable harness, and a smaller split loom for the alternator wire, and routed them next to each other, since they are going to the same location. Brian

I had a similar problem with a shorted wire, it only appeared when I started my truck, I had determined it was the alternator control line from the pcm to the alternator. I would start the engine and test the wire, but it was ok, but the alternator line had sensed a short and shut down. It turned out to be the wire loom routed under the oil dipstick tube, it rubbed through to the wire shorting it to ground, but only when the engine shifted from the motion of starting, it took me a while to figure it out. I connected my volt meter to the suspected wire and moved all the wire loom cables around until I found the one that changed the status of the wire to ground. You may try shifting/moving the wire looms to look for a change, and hopefully you can locate it. Brian

Well, fixed the problem; My brother happens to work for a Dodge dealer in the service department, and just happened to be visiting this week, so he quickly ordered and brought a pcm, and his scan tool. We did some testing and determined the problem is in the pcm, so we replaced it, after we started the vehicle we still had the same problems, after much head scratching we determined one of the outputs had shorted to ground and blew the pcm again. He was about to order another pcm, but we looked at the system one more time, I noticed the blue field wire to the alternator (+12 v) appeared to short only when the engine is started, and ok while running, so we shut it off and checked continuity on the blue wire while moving the wire harness, we found the problem was the blue wire just happened to be on the outside of the wire bundle and about 1-1/2" of unprotected harness was rubbing on the painted oil dipstick tube and finally wore through the paint and the wire insulation and shorted causing the symptoms I noticed. The harness just lightly touched the metal so it only shorted when the engine torqued from starting, so we were not able to find it at first. Fortunately the pcm is not blown, but simply shut down due to the intermittent short. Apparently the pcm is a very reliable unit, the problem is caused by some outside source. So, glad to have my truck running again!

I cannot trust the local dealer with an oil change, and I don't have the time to dirve further to the next town to try them. I am going to order a pcm and see what happens. I found a site called Dodge PCM Direct, anybody have any experience with them or any other sources?

Ok, I swapped the transmission related relay in the fuse box (engine compartment) with the highbeam relay, checked the related fuse-good, still no change. Looks like a new pcm.

I will check power to the pcm and fuse, and swap the trans relay.

Ok, I can try to power the alternator manually and I am sure it will work fine, because I don't think the problem has to do with the alternator; as all the other stuff happened at the same time and is on the pcm control list too. If I can determine the pcm is the source of the problem; where is the best place to buy one?

Mike, I live in Idaho and it's 105 now, but it may have something to do with the thermometer mounted on the opposite side of a metal wall. Brian

Both batteries were replaced last year, I have been charging them with a battery charger each night as I am driving it each day. I checked the field wires at the alternator and both have less than 2 volts reference to ground. The charging system and voltage gauge is the easiest indicator I have to note if there is a problem. The list of issues is more than just the charging system which leads me to think the pcm is not working right. Today is the first time I have driven the truck for any distance and noticed the A/C shut off, it was blowing nice and cold. The A/C is also controlled by the pcm. I read the codes with the key method and show: P1682=charging system voltage too low. P0753=Transmission shift 3-4 relay circuits. P1765=Transmission 12 volt supply relay. P1693 DTC detected in ECM or PCM. I am hoping to perform a "test" of some sort to determine for sure if the problem is really in the pcm before I replace it. Also; I have a 1999 ram almost the same vehicle options, Anyone know if that pcm will work in my 01?

Well, I started it up, and.....No change, still not charging etc. I still need to have that DTC code read, but not looking good. Anything else I can try to determine if I need to buy another pcm? Where is the best place to buy a pcm that is going to be reliable, this is my work truck.

I just pulled the air filter housing to get to the pcm, found the air filter really needs to be replace(!) Removed the pcm, cleaned the ground contacts, the screw with the ground lug had some corosion looking film on the aluminum surface, also cleaned the other two screws applied dielectric grease to all cleaned surfaces. Treated the ground wire near the battery the same as above. Removed all three plugs on the pcm, inspected the contacts, all are clean, and straight, made sure the connectors are put back in tight. Put the pcm back in and will try it tomorow.

What fuses am I looking for? Engine fuse block only? Error codes all relate to charging issue, no suprise there, the only one I cannot read is DTC on ECM or PCM... The grounds "look" clean I have not had time to remove and clean them. I question why some stuff works and some does not, is this normal when a pcm fails?

I was driving in hot weather up hill last week (dont know if temp related), when the "Check Engine" light came on, I noticed the volt meter was all the way down to the left most line (same as engine off position). When I arrived at the top and started on the decent; I noticed the overdrive does not work (auto trans), also the cruise control is not working, and the trans appears to slip on take off. Referencing the PCM (power control module) info; the pcm controls the above items, I have not noticed any other items on the list malfunctioning. Before I spend $400 or more for a new pcm, I would like to make sure it is the module or bad connection, ground... What is be best method to confirm the pcm is good or bad? Or is there something else that could cause the above problems? Brian

Yeah, I kept meaning to check the brakes, I change the tires out every winter and spring (snow tires) but forget to check because it's less than ideal weahter conditions, cold and raining. From now on I will be checking them! Live and learn.

FOUND THE PROBLEM: I was running out of time so I took my truck to Les Schwab Tire and brakes, to see if they could find something. They did find the front brakes needed to be replaced, and the rotors were too far to surface, so I had them do the brakes which included fluid flush etc. a little while later he came in and showed me cause of the pulsing; the rear rotor was worn down so far the vent vanes where showing through! The vents that where protruding where rubbing on what was left of the brake pad and causing the pulsing, the weird part is we both thought the problem was in the front axle area. I know, I should have checked the brakes sooner, had that nagging voice in my head for the last year or so. So, that's one for the books, brakes can be the cause of all kinds of noises and vibrations. Thanks to everyone for the help!

OK, finally had time to check the wheel bearings; jacked up both front wheels, one at a time and using a bar tried to move the tire by putting the bar in the spokes of the rim and rock the wheel. I was not able to detect any movement, I put one hand on the wheel to try to feel any shifing motion and could not, I then tried to move the wheel by hand to get a better sense of movement and agian nothing. I did this on both front wheels, they both seam solid. I slowly rotated the wheel and do feel/hear a slight "clunk" (did not sound right) much like the pulsing I heard before, I wonder if a u-joint would cause this. Any more ideas?

I had a similar problem my 4x4 went in/out, the vacuum shifter thing (cant remember the correct name) went out, replaced the part and all is good again, I got tired of chaining up the back wheels, but got real good at it. One thing I learned is the when the 4x4 light is on the vacuum shifter has shifted the axle fork in place to connect the drive line to the axles assuming nothing is broken. No 4x4 light no 4x4. So check to see if the light is on or off, it really does indicate something happening.

Well, I will just replace it this time, that way I will have a part that I can play with when I get more time.

I heard the bearing is a set or pack that is sealed and cannot be rebuilt, I suppose anything could cut into and be rebuilt, I am interested if it can be done reasonably.

Had not thought of a wheel bearing, I probably should have not driven where I did yesterday. The "pulsing" could be each of the bearings clunking as they turn. I will perform the tire thing; attempt to move the tire in a rocking motion not a up/down motion as I understand it. Either way if it moves I have some work to do; bearing or ball jount, I just replaced the track bar joint, so would surprise me if the others are going. Assuming the problem is bearings (sounds like the problem); what are sources of good quality bearings? I dont want the cheap China stuff, I like doing it right the first time. I have heard the bearings are a sealed "pack" how easy are they to replace? And is there anything else I should replace while I have it apart? I appreciate all the input. Brian

It does not feel like a warped rotor, I hear it but dont feel it in the brake pedal, it sounds like it is in the front axle area(?). I tested by braking hard in the snow coming to a stop and felt the brake pedal push back when the ABS started working. it is a sharp pulse very much like like the ABS pulsing but consistant and pulse frequency changes as the wheels slow down. I have a friend with a code reader, I will check for any codes. Brian

This started a couple of weeks ago and I cannot find any reference like it on this site; when I apply the brakes, I hear a pulsing sound only on the last few feet as I come to a stop, it sounds like the ABS system activating from a slipping wheel but I don't feel it on the brake pedal. I hear it only when the brakes are pressed, it feels almost like running over the rumble strips on a highway, the pulse frequency is related to the wheel speed. The ABS bulb passes the light test on start up so it is working, but the light does not come on to indicate a brake issue. Anyone have any ideas what this is?

I thought of that, I hate those quick disconnect fittings!, where is a good place to find ss hose and fittings?