bad compruter?

[swankmetal]

so, if the a/c, cruise, and speedo don't work, does that mean that the ecu/pcm is shot? if so, is it repairable? or does it need to be replaced?

 

[Philip]

If the VSS dies you loose the speedo and cruise controll. This is the Vehicle speed sensor. It is mounted on a right angle gear drive box on your transfer case. These right angle gear boxes are noted for going bad also.



Jack the rear tires up. Put jack stands under the rear axle. Unscrew the VSS from the gear box. It is mounted into the housing where the rear drive shaft comes out. Start the engine and put it in gear and watch the drive center and see if it turns. (Do not put the trans in park when you are done with this test. Just shut the engine down and let the drive train spin down). If the drive center was turning then you need to test the VSS.



Also check the VSS plug for corrision and chaffed wires. Check the wires up the harness as far as you can reach.



I have to head out for work soon. I don't have time to lookup the instructions for the testing. Do a search of this forium for VSS problems. You should come up with them.



Go into your user controll panel and put the state you live in. A lot of times there might be someone close to you that can help in troubleshooting.

 

[swankmetal]

well, i wore my eyeballs out reading the search results i found. i'm notso good with sparky stuff. one more thing, only happens once in a blue moon, but i've been sitting at a stoplight and seen the speedo jump to 70mph. dunno, but i will do some tinkering with the sensor today.

 

[SteamDave]

One other thing to check that I havent seen in the "speedo not working" threads is the nylon gear inside the transfer case (or transmission on 2wd)

Mine will get loose and slip on the shaft once everything gets good and warm in there. I haven't had a chance to take it apart to see whats going on yet

 

[cerberusiam]

If you haven't yet check the crank postion sensor for clearance, connectivity, and signal. they can go bad and do what you describe and the connection below the #1 valve cover can be bad and cause the problems. A crank sensor is considerably cheaper than a PCM.

 

[DKasper]

Your alternator won't charge either, unless someone's put an external regulator on. The truck will run just fine though -- I drove one of mine 100 miles with a blown computer. I replaced it with a reman unit I picked up for $250.

 

[swankmetal]

my cps wasn't even hooked up until about a month ago. i thought the only thing that did was go straight under the dash for a tach?? i would like to check it though. what kind of signals should it be sending? in an old post i found these:



Outer black wire on the under dash tach connector is ground, this goes to the - screw on the tach.

Inner black wire on the connector is switched 12 VDC, this goes to the + screw on the tach. NOTE: remove the 24 to 12 volt resistor from this terminal, and wire straight to tach.

Grey wire on connector goes to the S (signal) terminal on the tach. The harness instructions tell you to use the line with the filter in it (white), mine did not work this way, I had to wire it without the filter (yellow).



does that sound correct? what kind of signal should i be getting off the grey wire?

thanks for the help

dave

 

[tugboatphil]

Swank,



I'm sure you probably thought of this already, but check the connector pins inside all the plugs. Philip was troubleshooting my system and found a couple that were close to becoming a problem. Used a small pick to pry the connector out so it would make good contact.

 

[cerberusiam]

The CPS tells the computer the engine is running so it will charge, AC will work, etc, etc. If it is not working correctly you loose portions of the functions and am not sure which ones. If the truck still charges OK and the rest doesn't work it could very well be the PCM bad. Not sure what the signal should look like or be from the CPS. Anybody with an FSM got an idea?

 

[Greenleaf]

The controller will control the A/C system function(s). Not all functions but some. It uses a signal from the cycling switch to turn the relay on/off, by grounding the relay. The FSM also states that the controller will turn off the A/C clutch (for diesel applications) when the throttle is in WOT position. Still trying to figure that one out.



And another bobo..... the wireing diagram has an electric fuel pump relay wired into the controller, again for diesel application... ... ... ... ... ... ... I dunno who wrote this stuff.



-S

 

[Paychk]

The FSM also states that the controller will turn off the A/C clutch (for diesel applications) when the throttle is in WOT position. Still trying to figure that one out.



And another bobo..... the wireing diagram has an electric fuel pump relay wired into the controller, again for diesel application... ... ... ... ... ... ... I dunno who wrote this stuff.



-S

What year manual do you have and is it a FSM? I have never noticed that in the 4 manuals I have all published by Dodge.

 

[Paychk]

cerberusiam



The FSM doesn't get specific enough to state the type of signals the sensors produce.

 

[cerberusiam]

The FSM doesn't get specific enough to state the type of signals the sensors produce.





Of course not. What was I thinking. :{ :{

 

[Paychk]

:-laf Oo.

 

[Greenleaf]

Dodge FSM

I have a FSM that is one year old. When I began to read through this thing I was dizzy and nausious. It's very difficult to digest this. For instance. The engine controller is located with the diesel fuel system



The wire diagram has an electric fuel pump relay.



The Engine controller monitors the throttle position for a diesel and shuts off the relay when it reaches WOT.



Much of the info is helpful, however because the FSM includes mostly all gasser truck info, one has to tip toe trough the information diligently.



I read on these forums that the FSM for 93 model year trucks has the info to rebuild the 5 speed manual transmission. Mine is a 92 model year and it lists the Manual Trans. used behind the diesel engine, whatever that thing is called, Getrag G_ _ _ something or other. Don't know why you guys have to get the 93 model year just to have the rebuild specs. on this trans.



If I remember right, It lists something about locking torque converters and the NV4500 transmission etc. etc.



The 518 transmission is called the 46RH or something like that. (I'm not currently looking at my manual)



I'd be happy to look up some info for you guys, it's just takes awhile to find it and digest it. :-{}



Been reading this thing for a year now and just now beginning to understand the wire codes



GL

 

[Paychk]

Could you compare the diagram you have to this one?



https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=3751&width=4



this is from my original FSM that was published in 91/92 some time. I'm curious if there are any other descrepencies.



Thanks!

 

[Greenleaf]

Paychk,



I'll study up on that.



Last night I sat down again with my FSM and found some more good stuff, ahem! I mean I found another headach coming on.



The FSM (mine) lists the (for diesel trucks) A/C fuse linked with the wipers or windows. Don't recall exactly. However, upon examining my truck the fuse box isn't even the same!!!!!!!!!!!!!!!!!! OH MY HEAD HURTS!!!!!!!!!!!!!!!!!!!!



Who writes this manual anyhow, huh?????



There was something else I came across that wasn't even remotely close to what my truck has. Just wish I could have remembered what it was.



You guys are in for a real treat when you set down to trouble shoot an elect



BTW One would think that the engine codes would be in the manual. I have code 12 and there is no listing. Also have code 55 which I think is "end of code", code.



-S

 

[Greenleaf]

The other thing I just thought of is referece to the A/C cycling switch. The manual tells us that it threads into the H block (next to the low pressure switch) and seals with an O ring. Which isn't anything like our cycling switch.



Man I'd hate to have to work on vehicles to make a living and have to use this sorta manual!



-S

 

[cerberusiam]

Code 12 means a self check and dump of the computer was initiated. You should get a code 55 to start the dump and a code 55 to end it. Any numbers between the 55's are problem codes.



Pretty much all the computers DC used up to 96 used the same code sequences and meanings with some small variations depending on application. Allpar.com has a decent reference library.





I quite readin the FSM as it confused more than it helped. I just look at the pictures and diagrams.

 

[Greenleaf]

Thank-you. Thought I was going crazy reading this stuff.



I pulled my grid heater sensor and turned on the ignition. It set a code. I generally only have the 55 and now have the 12 and 23 I think it was and then the # 55 flashes.



I disconnected the battery and the heater grid code disappeared but have the A/C code. My A/C rarely works and that is why I have all the wire diagram for that function memorized.



-S