Archived 96, All Dash Instr. Stuck ON, No Tach, Low Volts

[LBrazdys]

Got a sensor today. Funniy thing is I had a tech at the dealer ohm it out. He also got zero or open in one direction across the two out side wires, and the about 3. 29 M ohm across the other way... ... ..... similar to what I read last night.



Now I'm thinking the problem is on the wiring harness side of the connector. I spent 104 bucks today... ... ... ... I hope this works.

 

[DavidC]

Got a sensor today. Funniy thing is I had a tech at the dealer ohm it out. He also got zero or open in one direction across the two out side wires, and the about 3. 29 M ohm across the other way... ... ..... similar to what I read last night.



Now I'm thinking the problem is on the wiring harness side of the connector. I spent 104 bucks today... ... ... ... I hope this works.

Wiring maybe, Could also be the signal portion of the sensor. That is what usually goes out on the later trucks. I know that part as mine did it. Put it in and you will be the first to know.



Dave

 

[LBrazdys]

Wiring maybe, Could also be the signal portion of the sensor. That is what usually goes out on the later trucks. I know that part as mine did it. Put it in and you will be the first to know.



Dave

Put in a new crank trigger... ... ... ... ... . no go... . still have the same problem. Remember back in my previous post I heard a loud clicking... ... ... ... the was the the AC clutch engaging upon the turn of the ignition key. I verified this by unplugging the connector.



So why is the AC called upon upon ignition w/out having the switch turned on? All of these issues seem to now point to the PCM box.

I took the connectors out from the PCM box and cleaned them as well..... no go.



I have a scan tool on the way. Any other ideas out there.



2 new batt's, 1 crank trigger and a lot of frustration.

 

[LBrazdys]

OK... ... ..... I'm about to give up.



310K, all stock.



2 new batteries

14 month old new Mopar Alt. (hmm I remember it doing funny intermitent things back then)

new speed sensor

checked all grounds and fuses



Why does the AC clutch engage with dash switch in off position. All other lights are stuck on. (water,trans,wait,engine & gen).



I have a feeling that I wont be able to get the codes out.



I am going to go over the PCM grounds and check the speed sensor at the harness (male end)



Any other ideas... ... ... ... i know this covered in other threads... ..... but I never saw any reference to the AC being engaged.

 

[DavidC]

Now that stinks. I am not sure you ever stated how this all started. Was it no charging,no tach,dash lights,all the above?. I take it the AC switch is turned off during this cycling. I hope it is not your PCM. I will look through some electrical diagrams but maybe someone else has some ideas. This is definately not looking good. I take it there are no TDR members in your area much less anyone with a code reader. Where are you?. Were you able to check any voltages for/from the sensor as K5IP explained?



Dave

 

[LBrazdys]

I have a scan tool on the way... ... ..... but like now I am in doubt for the first alt replacement to begin with. Also, I dont think the AC should turn on with the switch being off.



I still have a low charging state with the truck running. While running, the AC would stay on as do all of the idiot lights and no tach.



I have a bad feeling it is the PCM. Thats asking alot for a truck with over 300k, wouldnt you say?



Still, I am hoping it is something simple. Based upon the corrosion observed at the hood light fixture, Im guessing it would be wise to go over every connection on the truck.



Thanks for all you help... ... ..... this site is very helpfull.

 

[DavidC]

Might be picking at straws but does your speedo work?



Dave

 

[DavidC]

Forgot to mention the PCM provides the ground for the AC clutch relay after the appropriate inputs happen. There is a chance your problem could be at the power distribution center under the hood.



Dave

 

[LBrazdys]

I went over every ground I could find. Checked the drivers side engine strap, it was ok, Could not get to the other one... ... ... ... . kind of tight to get down there.



Also, how many damm bolts hold the drivers side batt tray down. I removed 4 of them. . looks like you have to go thru the fender underneath to get to the other ones.



The "wait to start" should cycle off. I hear the grid going on then off but the light stays on, as does the other lights. The AC relay trips the clutch without the switch in the on position is really troubling me. I swapped relay in thr dist. box, same thing.



Another thing, every once in a while the lights that illuminate the AC panel would flicker..... simple pat on the dash would solve that... . loose bulb.



My scan tool should be in today... ... ... ... maybe I can get to the bottom of this.



Also... ... ... where the heck is Ground "G119". Is that a mistake in OEM book?



Thanks

 

[LBrazdys]

Dont know if the Speedo works, I havent moved it out of the garage.

The O/D switch stays lit and wont cycle. No tach. Seatbelt and airbag lights cycle ok.

 

[DavidC]

You may have to unplug the PCM and start ohmming some wires to make sure you do not have some wiring/connector issues. I would try the AC first. Unhook batteries, remove AC relay,remove plug from PCM and ohm the ground side of the relay to a body ground. Should read open, if not there is a wiring/connector issue. I just went thru an ABS problem and the weirdest problem with connectors, almost went and bought anther ABS controller. The more electronics,the more problems. check it out.

http://turbodieselregister.com/forums/showthread.php?t=141080

It would be nice to find someone you could take the PCM to and have it bench tested. I do not know if the dealer is capable of doing this. I would not rule out the feedback in the harness or contaminated plugs.



Dave

 

[LBrazdys]

Ive read allot of post... ... ..... no scanner in the mail yet. I wish somebody would write a program to emmulate the PCM box like some have done for older HP engineering calculators. Seems like there would be a market for that.

Bench testing would be nice.



By they way... ... ... . where is G119 on the truck? That is the terminal end for the PCM ground but I'm not sure where that is landed in the truck. I think the OEM manual shows it for a gas engine (V-6?) near the AC compressor.

The AC panel switch is ok... ... ... . so someting inside the PCM box is telling it to switch on the AC... ... ..... unless a short is energizing the wiring to the AC clutch making it turn on... ... ... ..... I dunno.



Hoping UPS shows up tommorow

 

[DavidC]

I was just looking in the 99 service manual under Power Distribution. The diagrams show fuses feeding individual PCM plugs. Might be able to remove those one at a time and see if one solves your ac/overdrive and maybe some others or all. Might help narrow the search a little. Probably will not be able to start truck with fuse removed. G119 under connection locations just says "inline to engine ground" and no figure shown. Must be a secret. That Power distribution shows a massive plug filled with wires and a screw holding the plug in. Could be something there also.



Dave

 

[LBrazdys]

Thanks Dave... ... ... ... .....

I am feeling quite challenged at the moment.....

Cant wait to solve this puzzle. I traced all the wiring back from the PCM box along the firewall connectors etc. There are 3 connectors at the PCM box... they are all clean & tight.



This may sound stupid... ... ..... I changed the transfilter gasket prior to this failure... ... ... I dont hink anything down there would have caused the problem... unless for some reason they wanted the batt's disconnected for doing that procedure. Need to look that up. I know there are a few electronic components above the pan.



Again thanks all.



Gotta go..... till tommorow.

 

[DavidC]

No need for Batt. disconnect for that. Possibility of pinching a wire with the pan or filter inside the trans. though. I do not see any directway to isolate the trans the book shows wires directly to C2 (PCM). There has to be a plug on the trans. . I would crawl under and unplug everything to isolate and see if that cures most of your problems.



Dave

 

[LBrazdys]

Looks like I lost power to the mirrors, radio and courtesy lights as well. This is looking possibly like an ignition key/ground problem now. Radio was making a poping sound when it was working upon turn of the ignition key.



I took apart the PDC box and cleaned it... ... ..... I couldnt believe how much debris was inside the box. Still need to get to the pass side engine ground.

Maybe Ill have a scan tool today.

 

[LBrazdys]

Getting close to the cause... ... ... ... ... ... at the PDC. . fuse link number 3 (40amp) keeps blowing upon turning the key on. Note that his fuse link and number 8 are grounded at the PCM. I havent got my scanner yet.



I fixed the mirror courtesy light issue... ... ... ... blown 15 amp

 

[DavidC]

Getting close to the cause... ... ... ... ... ... at the PDC. . fuse link number 3 (40amp) keeps blowing upon turning the key on. Note that his fuse link and number 8 are grounded at the PCM. I havent got my scanner yet.



I fixed the mirror courtesy light issue... ... ... ... blown 15 amp

Have you found it yet?



Dave

 

[LBrazdys]

No I havent yet... ... ... ... . damm vendor sent my scan tool US Mail... ... go figure.





Anyway... ... ..... I keep blowing the 20 amp (not the 40) at PDC. Its the little blue fuse. The only thing on that circuit is one splice to the power outlets and there ok... ... ... ... the other path goes to the ignition switch.

I've blown 4 of these at 2. 99 a piece.



I think the this circuit is grounded thru the PCM.



I was going to disconnect the PCM, pop in a new 20 link in the PDC and see if it blows. If it doesnt, I would say the PCM is shot. If it does blow with out it commected... ... ... ... ... then someting may be wrong up in the ignition switch.



What do you think guys??



Oh yes... ... ... where can I find a used PCM or new one at a fair price?



THANKS

 

[DavidC]

That is different in 99. Fuse L, 20 amp at PDC feeds the power outlet only. Although it does feed with all circuits to the inside of the cab thru C134 which is the large white plug to the left of the steering column and the brake pedal. It is held together (male to female) with a bolt.



Dave