Engine/Transmission (1994 - 1998) No overdrive, No tach

[wannadiesel2]

My 95 2500 4x4 suddenly quit shifting into 4th (auto) and I noticed the tach wasn't working then the speedo wasn't either and the alternator quit charging! I shut it off and started it back up and everything worked, , for about 6 seconds then the same thing first the tach then speedo then alternator, no shift into 4th. This has got to trip someones memory. Only thing I know that is related to all the above is the PCM. Please tell me its something else simple. Thanks for any sugestions.

 

[mwilson]

I think that the crank sensor can cause those issues, at least for charging and the tach.

That is what tells the PCM that the engine is running I believe.



Mike.

 

[GAmes]

Can trial members use the search? A really good tool for a question that has been answered dozens of times. You probably need an engine speed sensor. It is mounted to the front of the engine, just above the damper. About $72, available here. http://www.genosgarage.com/prodinfo.asp?number=3924432

 

[Missouri Mule]

The Engine Speed sensor can cause all you problems ( but having the speedo go out on it, I've only comes across a thread or two where the ESS was the problem but combined with the other symptoms it is the ESS ).

 

[wannadiesel2]

Thanks for the responses! Would the PCM not see this as a missing signal and set a code? I have been a member for years why a trial member?? Do you have to subscribe to TDR?

 

[LandShark]

Check your codes and tell us what you find. If the PCM is the problem it will have numerous codes set or maybe you won't be able to get any codes at all.
There is no crank position sensor on your engine; it's called an engine speed sensor (ESS). PCM needs to see a signal from ESS for tach, AC, alternator, cruise control and OD to work.
Are the grid heaters working normally?

 

[wannadiesel2]

Thanks Shark, I checked the codes the other day and got "55". The grid heaters appear to work normally. Will a OBD 1 scanner help me at all? I can get one from the Irish Moffia.

 

[hsmith]

You must be using the key on-off method. If so, I'm sure "55" means system passes.

 

[LandShark]

The ODB scanner for '95 trucks would be a waste of money. All codes can be read thru the key method. The 55 indicated everything is OK. Check the 12v supply wire to the computer and also the wires going to the ESS. A bad wire on either can cause the problems you mention. Tracking down the computer 12v supply will require a factory manual to locate the wire and plugs. It runs along the firewall and goes thru one of the 3 plugs on the driver side. If wires look OK, I would start by replacing the ESS.
ESS is fairly easy to replace, is easy to obtain and under $100. The computer is harder to find and closer to $500: many places advertise that they have they them, but when you go to order, they are out of stock. I bought a remanufactured one from a Dodge truck dealer.
Don't give up. I spent several weeks trouble shooting a similar problem a few years back. It may help to read my posts from back then.

 

[wannadiesel2]

No overdrive no tach

Hey Landshark, took me a while to get parts. (long story, Orielly well never mind) So I replaced the sensor on the Damper, at this point I don't know what the hell its called. ESS or CPS either way I replaced it. Here is what I found: It is hard to get it calibrated, the old one worked but quit after a few seconds. After the new one installed and set as low as I could get it the tach works, the Alternator works, the speedo does not and it still doesn't shift. Obviously if doesn't know its moving it sees no need to shift. Now what?? I don't know if I had two problems or if the first one is just not quite right. Appreciate any help.

 

[hsmith]

You may want to look at the VSS which should be in the transfer case on the tail housing. The CPS aparrently fixed the charging problem. That gap should be . 050 also.

 

[BDaugherty]

There should be a connection at the top front of the engine where the crank sensor wiring plugs into the engine harness. Look real close there. I have seen connectors pulled apart as well as chafed wires in that area that caused the exact problems you described.

 

[Missouri Mule]

wannadiesel2, you can use 4 to 5 business cards to set the gap on the ESS(engine speed sensor)/CSS (crank speed sensor)/CPS (crank position sensor) depending on how thick they are.



The ESS fixed the charging problem did it fix the tach problem?

 

[LandShark]

I used a match book cover to set the ESS gap. One layer thick. Just needs to be close without touching. Check for codes again; maybe something will turn up.

 

[Missouri Mule]

From 96 FSM. This is for 47re (electronic) not 47 rh (hydraulic) but the mechanical components shoudl be the same.

No 3-4 (overdrive) upshift:

1. Dash o/d switch in off position.

2. Overdrive circuit fuse blown.

3. O/D switch wire shorted/open cut.

4. Distance or Coolant temp malfunction ( I think they mean trans fluid temp sensor).

5. TPS malfunction.

6. Neutral switch to PCM wire shorted/cut.

7. PCM malfunction.

8. Overdrive solenoid shorted.

9. Solenoid feed orifice in valve body blocked.

10. Overdirve clutch failed.

11. Hydraulic pressure low.

12. Valve bodyvalve stuck.

13. O/D piston incorredt spacer.

14. Overdrive piston seal failure.

15. O/D check valve /orifice failed.

 

[wannadiesel2]

No overdrive no tach

Sorry it took a while to get back here. Thanks for all the help. The CPS fixed the tach and alternator problem. After digging a grease pit (wanted one for years, got 5 acres why not!!!) I checked all the wiring around the speed converter that goes to the GV overdrive and found a wire that had fell down enough to touch the drive shaft and rubbed a small small spot in the insulation all the way to the copper. Now the speedo works and it shifts fine. You guys were all over it. While I had the hole in the ground I replaced the vac sw on the transfer case and the harness and the 4 wheel drive works too. I am a happy camper right now, MY TRUCK IS BACK! Next,,, fix the leaks!

 

[AWeis]

no overdrive no tach

check your tps i had the same thing like i went in the devils triangle replaced tps and was fine.

 

[moser11]

There should be a connection at the top front of the engine where the crank sensor wiring plugs into the engine harness. Look real close there. I have seen connectors pulled apart as well as chafed wires in that area that caused the exact problems you described.

I had the wiring harnes in this^^^area short against the head... turn the key on and wiggle the harness... . the grid heater solenoids will click if there is a short to ground... just a thought