12V 2nd Gen Cummins no tach, a/c, cruise control or 4th gear (o/d) solved

A common issue with 12V 2nd Gen Cummins Diesels. Having a part repaired twice is frustrating. Don't just assume that it is only the PCM in any case. I went through everything before finding out the PCM had not been repaired correctly the first time.
SIA Electronics made a faulty repair and also did not re-gel the circuit board.
Cardone did a suburb repair and the new gel made it look like it just came from the factory.
Other parts that were replaced that could relate to the issue: Engine Speed Sensor (ESS); Throttle Position Sensor (TPS); Vehicle Speed Sensor (VSS).
Vehicle: 95 Dodge Ram 3500 12V Cummins 47RH.

[@Nonsensenoalph]

2001 changed the cam sensor my truck doesn't have a crank sensor I changed the tps the ecm and now Im going take a pcm off my other truck and see if that's the problem . I wish there was a electronic delete that had to a mechanical injection pump and vacuum wastegate like the old 3506B model cat. I know they had problems too but I put hundreds of thousands of miles on several trucks and I can only remember a half of a handful of times I was at a repair shop

[@jimkillen1065]

OK I also have a 95 4x4 that did that crap a few years ago and I asked on the forums and every one said no way its the pcm. . I tested this and that finally is said we'll it's my money my truck and orderd a rebuilt unit from dodge and it was a on line dealer . Lot cheaper OK. Sure enough that fixed all problems but one . That was hit a small dip in the road the brake peddle would move and drop out cruise and overdrive . A big spring on peddle fixed that. Later on I heard others were also getting bit by this problem. So I told them what I did .

[@Kettenhund75]

What did you pay for your PCM?

[@collinking1438]

thanks my truck has these same exact issues same year and everything. Got the whole trans rebuilt cause of it. $3000 later still no overdrive.

[@anonknowledge]

Check your Engine Speed Sensor (ESS) gap. It should be .50 mm. My tach started to bounce again erratically at wot. I decided to check the ESS because I remembered it had somehow went out of spec before. I used a business card and it was to tight. Readjusted it to .508 mm and now it works properly.

[@anonknowledge]

What year is your truck?

[@anonknowledge]

Another thing that can affect the OD is the brake pedal sagging. Use your foot or a small bungie to hold it up to test it. Be careful not to put to much pressure on it.

[@danielstanton5808]

Can I limp a 98 12v home without a pcm? I’m picking one up an hour away.

[@altadutch]

I also lost tach, speedo, overdrive and cruise in my 95 Cummins. How to check the sensor, it’s in a pretty tight spot? Only 115k miles on my truck.

[@anonknowledge]

Unless your ripped, you should be able to easily reach down and slip a guage in between the sensor and harmonic balancer. A matchbook or business card is about the same size, but harder to feel if the sensor is set correctly. Tightening it if it needs adjustment is the challenging part. I have had the sensor come loose. Check the space, re-adjust if needed. Re-check it again. Otherwise, you may have to remove the sensor for further inspection. Do you need the diagram from the manual?

[@mftradu]

First thing to do you should check your PCM 5 volt refrence wires. First unplug the CKP sensor you will see 3 wires in the harness. Violet/White wire should be 5 volt reference voltage. The Black/Blue wire should be sensor ground. The Gray/Black is the signal wire and should have a 5 volt square wave output while cranking or running. If you dont have the 5v refrence replacing the sensor will be a waste of money and time. If you have voltage that means PCM and wiring is okay and you have a faulty sensor . If that is the case you can check the resistance between the wires on the CKP sensor with a volt meter. Reply here if you need more help.

[@anonknowledge]

I apologize @altadutch, I just read your comment posted on the updated video to this one. Are you able to try @mftradu's method for testing?

[@altadutch]

You guys are awesome. I have not yet focused on checking voltages as my eyesight is not the best. Did your check engine light come on? Mine did not and autozone cannot scan it in that case. I have an appointment scheduled with a mechanic next month so we’ll see. I’m considering having the css replaced to start.

[@anonknowledge]

@@altadutch I never had the CEL come on other than during a start. I have heard of guys having it flicker intermittently, but along with the Wait to Start and Water in Fuel lights as well. Tell the mechanic about @mftradu's method. Sending the PCM in to Cardone would be beneficial though, as there are components that will need replaced eventually. And Cardone re-gels the circuit board. Like @mftadu said, guys have sunk a substantial amount of time and money without even solving problems on these trucks. Hope the videos and comments help in solving the problem efficiently. Interested to hear what you find.

[@jesusjhernandez4911]

Cardone how i can contact them ? I have same problem No charging, no a/c , no 4th 2002 dodge 3500 cummins 47re transmission

[@lhermanrivas2462]

I have the same problem with my 1998 ram when the rpm goes down Stop charging a c stop working and check gages some times works perfect send my pcm to cia and they found nothing wrong what do you think take to napa or find a used one?

[@anonknowledge]

I went through all the electrical wires in the engine bay and also checked the under carrage wiring. I replaced all sensors. Check your Engine Speed Sensor (ESS) measurement from the harmonic balancer again. Otherwise, if you don't have access to a spare PCM to test with, Cardone through NAPA is the last resort, especially if SIA is reporting nothing wrong with it. Sorry, I am not being notified when comments are posted.

[@sendittrucks]

How long did this take? I just dropped mine off at O'Reilly and they will send it to cardone

[@anonknowledge]

Like 3-4 weeks without looking at receipts.

[@cholochedd6752]

Would that also cause a limp mode?

[@anonknowledge]

It sounds like something internal in the transmission. Is it intermittent? The PCM with other components can prevent overdrive from engaging, but that is not limp mode. I'll check my manual.

[@cholochedd6752]

@@anonknowledge it started as no overdrive then now it’s like in 3rd gear and not charging when on. Changed battery’s and alternator.

[@anonknowledge]

@@cholochedd6752 It's hard to say what it could be. I didn't find anything specific in the service manual, but I haven't had much time. Have you searched threads on the forums of various websites on the web?

[@cholochedd6752]

@@anonknowledge I’m going to try to send in the ECM hopefully it works

[@mftradu]

Guys, you should do a few simple tests before sending out your PCM to some repair shop. First thing to check is your 5volt refrence, at CKP / TPS and VSS then if your PCM is getting power and puting out power/communicating. A bad Crank Sensor, TPS sensor or VSS can cause lots of problems on these trucks. There is no LIMP mode on these trucks, the so called limp mode is your transmission solenoids not getting power therfore your truck starts in 2nd or 3rd gear when you put it in Drive (manual trucks exception here) I will make a video on how to trobuleshoot this on a 1997 4x4 3500 and 1997 3500 2WD soon. We had a client with a 95 3500 2WD Cummins automatic... the guy had his transmission rebuilt 4 times at 3-4 different shops around Phoenix (close to $20000 later) to find out everytime he went on a road trip from Phoenix to his weekened getaway home by Lake Mead the problem with the transmission popping in and out of OD and lock-up. A simple diagnose we found out that the in-line transmission temp sensor at 72F ambient temp was reading 280F to the PCM and at 80-85F ambient was reading 205F ... A few resistors $2.50 at Fry's electronics added on the harness at the sensor solved his problem for good. Do your homework before you start throwing parts and money at it. Also remember in today's world a new part is not necesarilly a good one.

[@CLCBill]

My 98 12 valve just started doing almost exactly the same thing as this, today. Out of nowhere, but its been a while since I ran this truck. The tach is extremely erratic and bounces. The truck dings at me as if it was turned off and on quickly. The dash lights flash when it does this too. Not constant, completely erratic but seems if I put into neutral while coasting it does it less then when in drive. All the other gauges were being erratic as well. Wouldn't shift into OD. I actually thought it may be my transmission at first because besides no OD, 2nd and 3rd were acting really strange. Almost like they were slipping but not. First and reverse fine. After seeing this and some other things I'm wondering if could be so lucky and just be the ESS. Of course I guess the PCM would be a possibility too. Any tips or words of advice would be appreciated. Thanks for your time

[@anonknowledge]

KZbin is a joke. I never get notified of comments. As far as your truck, I would start with checking wires if it's been sitting for awhile, just to rule out mice chewing through the wires. Next, if possible, find another PCM to test with and rule it out without sending in yours (check with local diesel mech shops to see if they have one or access to one. A junkyard might have one sitting on the shelf too). Other than the ESS, I had the tach bounce come back about a month ago and am having the dash cluster sent in. I was told they have had issues with the soldering. However, with the tach bounce I have now, everything else works. I will post a video when I get the results.

[@jimkillen1065]

Check all your grounds first and battery cables

[@CLCBill]

Thank you fellas for the ideas! I hate when folks don't update, and here I am being one of them. Things got crazy busy, but seeing these replies now makes me want to update... 100% it was the Crankshaft Position Sensor, which that fixed it immediately. Being a work truck, this thing definitely is a bit rough round the edges but is a great truck overall.