Hey fellers,
I'm cracking my factory service manual now, but maybe someone can save me some time.
So, I just fired up my engine and notice that the factory tach is not working and the alternator is not charging. I figure it's a PCM issue so, I try the A/C. Compressor is inop as well.
Fusible links have been replaced with fuses.
Any advice is appreciated.

-Niemand

 

You might not have a signal from the crank "position" sensor. As I recall, there is a write-up for troubleshooting in the "sticky".

 

I'll check.
I think it must be something in the A21 circuit. As far as I can tell, everything works but the A/C, Tach, and Alternator. Those all share the A21 circuit.

 

If the PCM does not see a signal from the CPS it will not turn on the A/C or Alt. If you had an auto trans. OD would not work. If you go for a drive your CC doesn't work eather.

So stop worrying about circuits till you know the CPS is working properly.

 

Like Phillip says. However, it's pretty easy to verify A21, and that eliminates that. The CPS is a notorious culprit, well known in this neighborhood. Usually that, or one of the 3 connectors between it and the PCM will be the fault.

 

I got side-lined for a while with some non-Cummins related junk today. I'll get back to it bright and early tomorrow and report back. I bet y'all are right about the CPS. Thanks for the help, guys.

-Niemand

 

I checked the connectors leading to the CPS for keyed power and continuity, and inspected the wires between them.
I also pulled the CPS and cleaned it and the balancer up and gapped it at 0.050
Is there any kind of bench test I could do on the sensor to verify it's working/not working properly? A replacement sensor is $95.

-Niemand

 

Yes.....(grabs 8W electrical diagrams off shelf)
when connected (pierce or back probe):
tan/y 8V
blk/blu 0V
gy/blk 5V toggle to 0V (or maybe reverse) as notch passes sensor.

 

Thanks, Mr. Martin
Unfortunately, everything started working again before I could isolate anything for certain. I'm also prompted to finally buy a real quality multimeter. I always find myself doubting this cheap one.
I guess I'll just have to wait for it to quit on me again.

-Niemand

 

Always a good investment when you own an old Dodge. I keep a good one in the truck at all times.

 

Mine resides in the glove box.
I also keep a small tool box full of electrical stuff on the floor board. I keep various gauges of wire, crimpers, wire strippers, crimp connectors, heat shrink, tape, solder, soldering iron, and a test light in it.

 

Typical for a CPS failure. The CPS has to work as well as a cable in a pretty windy environment. The 3 pin connector can get flakey, as well as wires near it if they've been pierced and not sealed. Then there's the 10 pin connector under the intake manifold, and then the connector on the PCM.

Good luck to ya.

 

Thanks, Herr Martin
I think I'll buy a new CPS when pay day rolls around. This one has the original engine paint on it with north of 300,000 miles.

Niemand Besonderes, out.

 

and maybe an order form for a new dodge?

 

Never!