Need95-00CTD

Like it says, Driving down the highway at 65mph, all of a sudden the speedo drops, along with the tach, and the truck shuts off...I got it pulled off onto the shoulder and got the hood up, and sure enough, the shutoff solenoid is dropped. Even with the switch in the "ON" position it will not stay up if I push it first. I have nothing with me, so I end up using my power cord to the Sirius radio to hold the solenoid up.

I get back in the truck and fire it up no problem, look down and I have no tach, no speedo, and the voltage is sitting at 11-12v, instead of the usual 14v. I drove it home, and it seems to run fine, but still the electrical is shot.

I tried searching for similar problems, but all I could find that was close was with 1st gens, saying a possible Crank Position Sensor. Is this possible? Would it just shut the truck off that quick?

I would really like to get the truck working properly ASAP, and it seems to me the lights keep getting dimmer (could just be in my head, but I doubt it). Any help would be appreciated.

GAmes

That would be the first thing I would look at. Make sure the ground wire is making good contact. .050 inch clearance from the damper.

TIMMY22

Dumb question, but is the belt still on?

Need95-00CTD

Hahahaha...Its so funny you ask timmy, I got halfway home and asked myself the same thing, thinking thats all it was and that I was an idiot for overlooking it, but no such luck... The belt is still on. I'll have to check the CPS tomorrow at the shop, hopefully thats all it is, but does that have any effect on the F/S Solenoid?

dieselman2300

Mine did the same thing and it was the crank sensor. Pull it completely off and check all the wires. One of my wires was completley cut. Just soldered some new wire in and gapped it with a playing card folded in half.
I think the playing card id INFIDELs trick, not sure though.
Alos, DO NOT USE crimp connectors, they will just corode and it will happen again.

TIMMY22

Check all your fuses in your power distribution box under the hood.

halbritt

No speedo, tach, or voltage regulation indicates that the PCM is not functioning. I had a similar problem just the other day. All the other gauges continued to function. However, my truck continued to run. There is a separate computer that controls the fuel shutoff solenoid. With the key on, the WIF and WTS lights also did not function.

Tate

According to the wiring schematics I've seen, the solenoid is just a switched source on the hold circuit, not computer controlled. Check to see if the solenoid is getting 12v at the connection with the key on. Maybe something is wrong with the key switch? Seems like the common link to me.

Need95-00CTD

I would think it would not have anything to do with th key. The reason I say that is because the radio works, the other gauges work, basically everything BUT the speedo, tach, F/S solenoid work.

Also forgot to add the WTS light and heater grid don't work.

I'm gonna pull the crank sensor and make sure its still working. Is there a way to test that its working while its off the truck? Thanks guys, I'll be checking back regularly!

Need95-00CTD

OK, new symptom just found.

I replaced the PCM with the one from my 98, as far as I can tell, its no better.

I used a DMM to check the voltage between the two posts on the back of the alternator to see if there is any voltage coming to them from the PCM, it reads 0V.

Does this mean the wiring is bad somewhere? Like a short?

At least I know now its not the PCM right?

Thanks guys!

vzdude

Check the 150A fuse in the PDC ( underhood fusebox) . The fuse bolts in right at the end of the pdc where the large wiring goes out to the alt. If you lost that, there would be no power at the back of the alternator.

vzdude

Also....the PCM grounds the back of the alternator at the field terminal.

infidel

There are three separate positive circuits going thought the key switch, perhaps only one is bad. Also it's quite common for the too tight wiring under the steering column cover to get pulled apart.

I know for sure the PCM from a '98 won't work on any other year.
In fact the only years that are the same are '94 and '95.

Need95-00CTD

Alright infidel,

I checked continuity between the positive wire at the PCM (white with purple stripe) and the positive field terminal on the Alternator and they are connected. I cannot find a green wire (negative field terminal wire) that runs into the PCM, it might be there, I just cannot find it, i figured it just grounded to the body or block.

So I am stuck using my 97 PCM. Is there anything other than the PCM going bad that would make the voltage to the alt read 0?

infidel

Like I said, bad key switch or wiring to it.