Katmandu

I have a 98 Dodge Ram 2500 w/Cummins Diesel. The instrument cluster gauges/needles recently stopped working. All the needles stay pointed to the left when the truck is started. They WILL MOVE about a 1/16" to the right.

When a diagnostic tool is used on the port, it shows NO Computer (ECM). Also, the alternator shows NO OUTPUT when connected to a battery/alternator machine!

The LCD odometer just flashes the mileage. The odometer is NOT racking up mileage when driven. Some idiot lights light up. The ones the do are random.

I checked all electrical connectors I could find under the hood and under the dash. I clean all the battery posts and grounds. My batteries are in good condition as well.

The alternator is NOT charging when the vehicle is driven. I was driving with the lights on and the battery was drawn down.

What's going on and what do I need to check out ?

sweeney186

sounds like pcm (on bulkhead) is not powering up-fuse ok?

Katmandu

Can you please explain further ? What is the bulkhead ?

Yes, all fuse are good.

sweeney186

bulkhead is the firewall & the pcm is located on the pass. side just behind the air cleaner(silver rec box) w/ 3 wiring conn. going to it.Black conn to pcm pin #2 light green & blue wire should have 12v w/ key on,pin #22 red white wire should have 12v all the time,pins 31,32 black/tan should have continuity to ground.Gray connector pin #12 light green black wire should have 12v key on.If all this ck out-the pcm is dead

Katmandu

Got ya. Great info! I'll check it out and report back in.

Need95-00CTD

Check the fuse...pull them all out, shine a light on them from behind, just to make sure its not blown...I looked and looked and looked...and it finally took me a DMM to check the continuity of all the fuses to make sure they weren't blown. sure enough one was. I'm still chasing down the short that blew it.

XLR8R

Sounds like you at least need a new alternator!

Katmandu

I'm not so sure about that.

The current alternator is only about a year old.

Also, from my understanding of the truck's charging system is that the charging circuitry runs TROUGH the instrument cluster (Voltage gauge - exciter wire). The alternator needs this input reading to produce any output voltage.

sweeney186

actually the alt (exiter) power comes from the pcm-if its not working-neither is the alternator

Need95-00CTD

Heres a quick test for you...do it carefully!

Turn the truck to the "ON" position, but don't start the truck, use a DMM or Volt meter to check the battery charge, it should be 11-13v lower since your alternator probably hasn't been charging them. Now, on the back of the alternator are 2 SMALL studs, that a black housing connects to. Check the voltage between those two studs...I think the bottom should be positive and the upper negative, but IDK for sure, its been a while. If its below 3v, your PCM is not sending it power, if its over 8v and the alternator still isn't putting out power (when running obviously) your alternator is fried. If there is no voltage, you have a problem getting power to your PCM like I did, which means a blown fuse or a bad connection somewhere. If the 98 is like the 97 your looking for a light green wire that has a black stripe on it. It powers other things like the F/S solenoid and grid heaters...so you'd know if it was shot (at least if the fuse was blown...if the connection at the PCM plug was bad you just wouldn't have a tach or speedo).

Good luck, hope this helps!

XLR8R

The OP said the alternator had no output on a test machine, so.... generally that means the alternator isn't working.

vzdude

I would bet that some place like Autozine or something just hooked it up in the parking lot. Definately sounds like an electrical problem. Something is locking up the bus communications for the instrument cluster. Probably the pcm, if I were a betting man!

XLR8R

That's true - I don't consider those Ghetto-Zone testers to be reliable... I assumed he had it bench-tested.

Katmandu

Been to cold to do troubleshooting.

But I've done more reading in the forums and found it "may" be related to the CPS or Crank Positioning Sensor (aka APPS)

How does one check the CPS to see if it is bad ?

BTW, the *********** wants $155 for a CPS.

Here's one On-Line for $73.

http://www.nextdayautoparts.com/sipc127.html

vzdude

Well......the thing is...the crank sensor won't affect the rest of the guages. Your original post said that all the guages were affected. The guages get all their information from the PCM over the CCD Bus. Something has the bus locked up for the guages to be fubared. Again.....I'll guess the pcm. Go ahead and check the crank sensor, but typically there are only a few other issues related with the cps, and ALL of the guages isn't one of those things. Good luck! Let me/us know if you need any diagnostic trees or anything.