Engine/Transmission (1994 - 1998) No tach, no charging, no a/c, no hair left

[Julie]

Hi all! This is my first post here, mainly because I have always been able to fix any issues with my truck.......until now. This is a 1995 with 210,000 miles on it. There seems to have been a progression to my issues or so I thought.

First Check Engine light came on. I tried the key method to diag. No helpful info there.

Next there was the Check Engine light, tach bouncing, overdrive going in and out.A friend is a Dodge diesel mechanic. He brought home OBD1 scanner. First attempt to read...no codes. 2nd attempt to read....no codes. Third attempt involved driving with the scanner in cab. The code would come in and then totally clear. The only code it showed was a high temp trans code. My friend felt that a bad ground could cause these issues. Looked at some grounds, they looked good. Changed all the cables off both batteries. Double cleaned the grounds on the engine block. Just in case replaced the Trans temp sensor (failed in the past.)

Test drove the truck about 14 miles. No issues. Stopped for about 15 mins. Started to drive home......no tach, no o/d, voltage slowly going south, no air conditioning. More research...Engine speed sensor. Makes perfect sense. Changed the ESS, went for a long drive. After 25 miles I stopped for 10 mins. 24 miles toward home, stopped again.... no issues. The last 500 feet check engine light bouncing , tach bouncing and wait to start and the rest on the right side of dash bouncing on and off. Acts as if there is a power loss then gone.

When the truck gets warmed up the issues start. Now I don't mean warm from driving. I drove it 120 miles on a Friday, no issues. Drove it home on a Sunday, no issues. Parked in front of the garage for about 1 hour....80 degrees. Started it to move it to our shop, no tach, no charging, no a/c. By the time I got it turned around and up to the shop, it had cleared up.

Started pulling the wiring harness apart. Heated the truck up so it would fail, moved the wiring harness around till we found a section that made the tach jump, checked wires could not find any issues. Just in case replaced 2 wires going to the ESS, just 18" of the wires. on the passenger side by the PCM. Checked voltage at ESS 5 volts, 8.4 volts, the ground was showing .oo6 on ohms to neg battery term. In checking that same wire from the harness at the PCM when the truck is warmed up, there is good continuity.

I have read as many posts as I can find on this type of issue and have tried to follow any clues that I see. Yesterday after the truck had cooled a bit I took it out to see if I could get the batteries charged up a bit. This is where the symptoms change a bit. Check engine light goes on and off, tach bounces around a bit, cannot lockout the overdrive. Since I had my radar detector in the cab, I noticed that the voltage would not go above 13.3 volts. I was expecting to see something around 13.9. I tried brings the rpms up to about 2000 to see if it would change, no luck. So now I am beginning to wonder if the alternator is starting to go. It is a Napa reman and is about 2 years old. The entire time I ran last weekend with no issues, the voltage was 13.6-13.7. I don't know if it matters but this started when I hauled a friends 7500 lb. trailer about 30 miles. Last year on a trip the truck started going in and out of overdrive on a trip when using the cruise control. We stopped using the cruise control, no more issues on that trip.

I realize this is a long post but I think it helps if I give all the issues and their order.

Thanks so much.

 

[MMeier]

When you changed out the ESS as you call it (CPS?) , did you load up the plug on the front of the head with some dielectric grease ?

 

[Julie]

On a 1995 it is called a Engine Speed Sensor and yes it has its share of dielectric grease.

 

[cerberusiam]

Probably time to change the SBEC (computer) out for a new one. All those functons are run out of or related to the SBEC in some way. They have a habit of cracking solder joints and when they get warm they go open, sometimes intermittently.

 

[Julie]

I don't mind to change the PCM if that is the issue. The PCM's are getting harder to find but I would still like to prove it to the PCM before I drop $600. Then there is the issue of getting my vin# into it which I think means I would have to go to a dealer. That also means a rehab unit because there are no new ones.

 

[cerberusiam]

Your truck doesn't really have a PCM and pretty sure it doesn't require a VIN program. Not sure where the break is but I don't think there were any issues with a VIN until you go into the programmable units in may the late 2nd gen or 3rd gen. The VIN is only needed if the ECU has a VIN and it is sharing data on a bus. A programmable ECU with a VIN was not present until the VP trucks came out in 98.

An engine control unit for a 95 list for $160 exchange where as the same thing is $400 plus for a 2001. Pretty sure all you have is the SBEC (single board engine controller).

Intermittent problems like what oyu ahve almost alwasy come back to the SBEC, that has been my experience anyway. That is not to say the alternator isn't going bad and dumping noise into the sytem messign things up, or, the SBEC connector is bad, or, a gorund issue or ????

 

[GAmes]

The FSM calls it a PCM in a '97. Semantics.

Although I don't have an automatic I had all the other symptoms. I paid tourist price for a new ESS at a dealer in Idaho, planning on replacing it when I stopped for the night. With a new one in the passenger seat the intermittent failures stopped. About a week later, in the safety of my shop, I wiggled wires while my wife watched the tach. One of the three wires coming out of the engine harness had a TINY hole rubbed through the insulation and the result was a dead short when it bounced on the intake just right. I now have a spare ESS.

Last year I had an alternator failure that I suspected was the PCM because the alternator checked good. I had my wife overnight my spare to me, and it didn't fix the no charge problem. Since I was far from home I wired in an external voltage regulator and completed my trip. Once home, I went thru the trouble shooting drill and found that the battery temp sensor was faulty. Replacing it didn't result in charging with the original PCM. A member of the TDR loaned me a spare he had for his '96 and it worked. On a whim I tried my spare PCM, and it worked also. The question, did the battery temp sensor cause the PCM to fail, vice versa, or was two components failing at the same time just a coincidence?

If you need instructions for an external voltage regulator let me know. I don't know if one would fix all the issues however. If you have a FSM it will give you the spec for the battery temp sensor (located under the driver's side battery).

edit; I trust you gapped the ESS correctly. .050 inch plus/minus .01 The book calls for a non-magnetic feeler gauge.

 

[cerberusiam]

Doesn't matter what the 97 FSM calls, the OP has a 95. It is definitely not semantically the same thing.

There is large difference between a 97 and a 95, even a 96 as mid 96 was the switch over to the RE transmissions which introduced the need for something close to a true PCM. An RH transmission has no controls, only the application of OD an lockup which is based on the TPS position. An RE has much more integration and requires a feed back system that dictates a much more complex operating system in the PCM to control correctly.

The 94, 95, and early 96 SBEC's were functionally little different than the 91-93 controllers. They did not need to be as all the functions they ran did not require any kind of adaptive interface. Hard coded ROM chips on a single board did all that was needed.

The SBEC's have a reputation for these type of failures where the PCM's did not. Any time you start move wires around close to the controller in question one has to consider the controller and the connector as part of the potential problem. Tension changes on the harness will make chnage the tension on the board as the connector is soldered directly to it. A bad solder joint can and will move on the controller by moving the harness a foot away from it. Another issue with the connectors is female portion of the connector can float in the connector itself and not make contact, or, expand and not make good contact. That contact can be compromised by moving the harness at any point that changes the tension on the connector.

The sheer number of problem areas suggest an SBEC problem, either that or a mouse has made a nest and chewed a lot of the harness. If the harness itslelf checks out, any connectors to the sensors and peripherals check out (those have to be checked for pin depth, seating, and contact also as that is a another inherent issue in older vehicles), then it is back to looking at the source of all the functions, the controller.

 

[GAmes]

Doesn't matter what the 97 FSM calls, the OP has a 95. It is definitely not semantically the same thing.

There is large difference between a 97 and a 95, even a 96 as mid 96 was the switch over to the RE transmissions which introduced the need for something close to a true PCM. An RH transmission has no controls, only the application of OD an lockup which is based on the TPS position. An RE has much more integration and requires a feed back system that dictates a much more complex operating system in the PCM to control correctly.

The 94, 95, and early 96 SBEC's were functionally little different than the 91-93 controllers. They did not need to be as all the functions they ran did not require any kind of adaptive interface. Hard coded ROM chips on a single board did all that was needed.

The SBEC's have a reputation for these type of failures where the PCM's did not. Any time you start move wires around close to the controller in question one has to consider the controller and the connector as part of the potential problem. Tension changes on the harness will make chnage the tension on the board as the connector is soldered directly to it. A bad solder joint can and will move on the controller by moving the harness a foot away from it. Another issue with the connectors is female portion of the connector can float in the connector itself and not make contact, or, expand and not make good contact. That contact can be compromised by moving the harness at any point that changes the tension on the connector.

The sheer number of problem areas suggest an SBEC problem, either that or a mouse has made a nest and chewed a lot of the harness. If the harness itslelf checks out, any connectors to the sensors and peripherals check out (those have to be checked for pin depth, seating, and contact also as that is a another inherent issue in older vehicles), then it is back to looking at the source of all the functions, the controller.

Blah, blah, blah. The OP calls it a PCM. What you call it has little significance. Other than the trans all the listed faults can be caused by a defective ESS and do not necessarily "suggest an SBEC problem". I have also read that a 3-4 shift problem can be caused by the neutral switch being open or shorted or a damaged switch wire to the PCM (loss of park/neutral input to PCM). Perhaps it is a faulty module. Why get your panties in a wad because we call it a PCM?

 

[surfbeetle]

My 95 did the same thing last month, I have 225,000 miles on it. I started with the Crank Position sensor from Cummins and thought for a couple of weeks that my troubles were over. Then on the next trip, the AC continued to die when I was stopped at an idle. Also had the electromagnet part of the three year old fuel solenoid die. My radiator and fan clutch were the originals, had them changed and was amazed at the difference in air flow in the engine compartment just idling with the hood up. My PCM, SBEC, ECU (whatever you want to call it) seems okay at this time. My point is that given the age of these trucks, you may need to also address these other items like I had to in order to keep the temps back by the computer in check.

 

[Julie]

Today I got the flashing 'Wait to Start' while I was driving down the highway. The truck had sat in a parking lot for about 10 minutes in the sun. I drove for about 15 minutes and it went away. Things cool down and go back to working fine. More and more I am thinking about the Powertrain Control Module ( just using the verbage from the part number.) Now the big question is.....the mechanic at the dealer says my vin needs to be put into the unit or there will be an ABS alarm. The truck will run fine just not use the ABS like it should.

Another point is the wiring harness. From the research I have done, none of the parts or pins are available to create a new connection to the Controller because of Chryslers policy of holding things out of the norm. Ford and Chevy could be purchased aftermarket Anyone have any thoughts on that? The connector end looks good as far as all the female pins being the same distance from the end of the connector and looking at them with a magnifying glass they do not look like they are spread open.

As far as gapping the ESS.....measured the old with business cards and set the new one the same.

 

[cerberusiam]

Do the other problems go away when it is cooled off? Tach? Cruise, etc?

I have chnaged them before and not had to do any VIN inputs. Was thta becasue it is not needed, or, the ABS was disabled and we did not care I don't remember. If it was th eolder style rar wheel ABS then don't think a VIN is needed. If it 4 wheel ABS that is different, but, never seen it on a 95 so have no idea what it would entail.

Dodge used oti have a book of all the connectors used on these trucks you could order new with pig tails on them and color coded correctly. Not sure it still exists. Could be the part sperson is totally unaware or it has gone to the after market.

 

[Julie]

Once the truck cools down by air movement or sitting in the shade each and every symptom goes away and the truck runs the way I love it to run. The truck has 4 wheel ABS and I would prefer it to work. Mopar does not seem to be interested in supporting older trucks.

 

[cerberusiam]

Of course not, they want to sell new trucks not fix old ones.

About all you can do is replace the controller and see if it needs to be programmed with a VIN. My understanding is the engine controller, ABS controller, and air bag controller are completely separate units on those trucks. Then again, never had this exact problem with one that had 4 wheel ABS.

 

[LandShark]

Flashing 'wait to start' is an indication that the PCM is bad. I went through this a few years back and did a thread in this forum, if you care to read it. The PCM in a '95 does not need to be programmed with a VIN (I'm not sure that the PCM program can be changed in any way on a '95). Many places on the web will show that they stock this PCM but when you try to order one, it is not available. My local Dodge dealer was the only place I could find that could actually get me one.

 

[Julie]

LandShark,

Glad you responded. I read your thread last week. Do you remember if the Wait to Start was on all the time or just when the engine was warmed up? My issue is not constant. Yesterday I pulled the cap off the Intake Air Temp Sensor when I had the wait to start and found no voltage on the leads. This morning I pulled the cap off with the truck running but no issues and there was 5 volts sitting there on one lead.

As I have said, I don't mind spending $$$$ when it is spent on a problem, not just replacing parts. Right now the question in my mind is "Is there a wire issue somewhere that is telling the PCM the wrong thing? or is the PCM slowly taking a crap?

 

[fest3er]

The problem almost certainly sounds like corroded connections somewhere. As current across such a joint increases, it heats up (just like an incandescent light bulb, but without the light) and generally increases the resistance.

Swap relays around in the PDC; you might have a relay or two going bad.

Check resistance through the ignition switch with it in the on and start positions.

Check the big connector(s) under the dash.

Look for places where wires pass sharp-ish metal; something could be shorting. (After disassembling my driver's seat looking for a problem, I *finally* saw a tiny blemish on the seat frame. Then I saw a corresponding blemish on a couple wires that pass over the frame near there. Sho'nuff, that's what was shorting and causing the auto-resetting breaker in the dash fuse block to greatly overheat. After taping the wires thoroughly and putting a bit of split-loom where the harness crosses the fame, the power seat controls have worked without trouble since.)

Unplug the positive cable from each battery and wait for capacitors to discharge. Then get an Ohm meter and start measuring resistance in 'wire' circuits. Anywhere you see more than ⅒-⅓ Ohm, start looking for something bad between the two test points. Especially check between ground straps and the negative battery connectors and between the positive connectors and various places fed from it. You might even check resistance between each neg. connector and between each pos. connector.

Disassemble your PCM-equivalent. Use a loupe to inspect solder joints and circuit traces. If you find bad solder joints, you can use a low power grounded soldering pencil to touch them up (re-melt them).

Test both batteries, make sure both are in good shape and fully charged.

Test the alternator, make sure it puts out clean-ish 14.8 VDC at around 130 Amps, both when cold/cool and when warm/hot. On a scope, it might show two or more 'upper halves' of sine waves. A bad diode will cause one or two of those curves to be flat, or short than the others.

 

[LandShark]

Julie: Fest3er has some good points. Several problem occurred at the the time when I had my PCM problems. The alternator was going bad and I could actually hear a whine from the radio because of a bad diode. (Don't forget that the PCM controls the alternator.) At the same time the 12v supply wire had corroded most of the way through where it had been pierced by a test probe a dozen years earlier (on the firewall, drivers side). Test the PCM supply voltage at the PCM with the truck running. During this time the PCM codes showed multiple sensor failures which did not make any sense. If you can't get proper codes, the PCM is not working.

As I recall, the 'wait to start' light was flashing at start up, but not when driving. The point is that the light should never flash.

 

[LandShark]

Once the truck cools down by air movement or sitting in the shade each and every symptom goes away and the truck runs the way I love it to run. The truck has 4 wheel ABS and I would prefer it to work. Mopar does not seem to be interested in supporting older trucks.

The ABS has it's own computer that is not connected to the PCM in any way. I'm fairly sure of this. Your ABS should be working fine.

It is possible to use the truck with a bad PCM. I did this for a couple of weeks when I had to use the truck for a couple of jobs. Install an external regulator for the alternator and install a switch to lock the torque converter (you really should have this anyway). You won't have 4th gear, AC, cruise control, etc..., but the truck will be usable.

 

[1workinman]

I just went through this with my 95 dodge 4x4 automatic transmission . First thing that happened was the power to overdrive lockout dropped out , switch in dash. Second was the ac stopped working. Tach still working then, and alternator. Got to a point when I hit a small rut in highway I would loose overdrive,crusecontrol and ac, the tach at that point still worked. I may have to drive 20 miles before those functions returned . A few weeks went along testing and I only use the truck to tow with on the weekends anyway. Got to a point that check engine light would flash , or water in fuel , tack would act in a non linear motion , ac stop working , power to overdrive lockout button not light up when pushed , alternator would overcharge or not at all . Stop truck and let cool off all functions worked good for a little while after sitting overnight. I tried to clean and tighten the harness to pcm not a easy thing to do for me . No help . I read on the net where a fellow took his pcm out of the truck and placed it in the freezer for a little while and returned to truck and his problems went away only to return after the truck was driven or idled for a while. At this point I ordered a rebuilt pcm from an on line Dodge dealer in Florida . I believe it was around 380 plus core charge. I installed the pcm and all problems went away . Finally . One thing if you have a automatic and the cruse is set and you hit a rut in the road even a small one and the tach moves a bit or you loose cruse control that probably is the brake switch. The peddle moves a little bit in the downward motion in the rut and it takes out the switch for a moment. Place your foot under the peddle and hold it up when you get close to one . This is on the inner state also not a dirt road just an uneven surface of pavement. Both the pcm and brake switch can cause some of the same problems but of course not all. Your problems could be something else but mine was the pcm . I gave the guys at the dodge dealer the vin number and ordered it . There was only one in the system. I was told all pcm are located in one ware house or that is what I was told , one year warranty . good luck Jim