Trying to help my dad out. 92 Cummins 4x4 suddenly lost OD and cruise. Speedo still works, so doubtful it's the VSS. Does anyone have a chart for troubleshooting? I am leaning toward the PCM died, but there are no codes in it.

OD is usually the TPS. I went through a few on my 92. The CTD is really hard on them. Growing tired of $300 sensors, I put a pressure switch on the OD and run it that way.

I wish I knew the answer on the cruise. Mine is dead too. I think it's the clock spring.


http://www.dieseltruckresource.com/dev/1st-gen-ram-all-topics-f93.html

TPS is good, I get a nice smooth range of ohms with no flat spots as the pedal is depressed. I will double check the voltage, but it was set about 3 months ago when I was fixing his A/C.

just had this problem on my 92 a few months ago. turned out to be ecm.

Although rare, check the connection on the trans temp sensor inline on the tranny cooler line. If faulty or bad connection, will not kick it in to overdrive too.

I have also read the coolant temp sender on the block behind the pump can cause issues. I'll double check all the connections; it is possible that something could be corroded thanks to the ice slicer garbage they put on the road.

Chris, how did you determine that the computer puked?

Could also be the speed sensor.

Ed

A 92 dosnt have too many electronics in the tranny, but the tranny temp switch on the cooler line could be reading faulty thinking the thing is under 20 degrees or so, whatever temp is the temp to keep the OD from coming on. I had a 91.5 and it would intermittently work, but was way worse in the cole, I had a part truck laying around, swapped that, and it repaired the issue.

As for the Cruise, how is your brake switch?

Brake switch is ok. It has been intermittently working. Sometimes it will go into OD and at the same time cruise will work. When it quits, they both fail. Appparently the volt meter is showing under 10v charging, then it will bounce up to where it's supposed to be. Have to get a meter on it to see what the real charging story is. I'm having pops clean the connector and computer pins to see if there is some junk that's causing the intermittent issues. Leaning pretty hard toward a dying computer. He wants to take it to the dealer for diagnosis, but that is 3/4 of the cost of a computer.

If they are closely related, you may be having a wireing chaffed, IIRC they share some of the same wires for power and ground, I dont have a wireing schematic handy, but maybee trace the wires back and see what you find.

My 91.5 was mouse ridden before I got it, I had a lot of little stupid issues and 99% off them were wires chewed on.

I will see if I can find ya a schematic and copy it on here.

I cant copy and paste the schematic I have becuase its on mitchell on demand and you dont have my sign in, or passward, so you will just get a blank page.

BUT I did see the cruise and the tranny thermal switch shafe a what looks like a sence return wire from the SBEC, so its could be the SBEC or the thermal switch.

I know Id be trying a temp switch.

I have a Chilton wiring diagram. Very generic, but it has color codes and most of those should be the same gas vs diesel on cruise and OD. I don't know if the gassers use a tranny temp switch, but will take a look at it tonight.

Latest update: A/C also doesn't work when everything else is down.

New computer = nothing fixed

Grounds checked, still nothing. Any other ideas?

go to dieseltruckresource.com or one of the diesel sites i am sure you will get more info than here.

too bad it wasnt the computer. that was my problem.

Quote:

---

A/C also doesn't work

---

One time, on my 92, the AC stopped working and when I went to put the windows down, they didn't work either. I don't know about the cruise control and overdrive because I only drove it to a shop less than a mile up the road to be fixed. Turned out to be the ignition switch. I have no idea if this could be your problem, I'm just throwing it out there because of the AC issue you mentioned.

Scored a deal on Sleazebay for a factory manual on CD as well as a paper Powertrain Diagnostic manual. He's not parting with the truck anytime soon so it's a good investment anyway. We will see what those turn up.

I didnt think it would be the computer.... that would have been my very last option.

Did you replace the temp sensor switch and speedo sensor? Those are both cheap fixes, and even though speedo is working, I've had my cruise work erractically because of the speed sensor had some "electrical noise" causing problems, but speedo worked.

What have you done with the TPM sensor? I can't remember...

The common tie to every single thing that works or not is the computer. It wasn't terribly expensive. I hate throwing parts at a problem though... I didn't make that decision, so have to pick up and regroup. We haven't done anything with the temp sensors. TPS has been set and also checks out for smooth operation. With the manuals on the way, I think we should be able to ferret out the offending issue.

I would check the plug for the speed sensor on the front of the engine. If it is unplugged, or poor connection, the charging system, and the a/c won't work. I imagine the od and cruise won't work either because the trucks ECM doesn't know the engine is running without input from the speed sensor on the front of the engine. If the ECM doesn't know the engine is running, then many things won't work.

The speed sensor reads off notches in the dampner, and the plug in the harness is right next to the thermostat on the front of the engine. I fought my a/c and no charging for better part of a week before I had found the harness unplugged to the speed sensor. My truck is a 5 speed, so I had no problems with trans shifting.

Michael