Humphries93

Howdy gents, been having a wiring issue since I got this truck and I'm almost out of ideas.
Truck has:
​​​​​​No speedo
no A/C
No cruise
No tach signal
And no odometer

Truck does charge because previous owner had hooked up an external voltage regulator.
Figured it was a CPS issue, I'm getting 3.5 volts to the two signal wires, ground is good. Is that enough voltage?
I've also checked pcm pinouts and I have no constant 12v to PCM pin 3, but pin 9 (12v ignition) and grounds 11 and 12 are good. I've jumped 3 and 9 together with no change.
I don't know the pinouts for the ASD relay but I have no ground there at pin 85? I think.

No blown fuses, I've swapped asd and ac relays, no change. I'm either at a new CPS or new PCM but I don't think either will fix the issue.

Sorry for the novel, any ideas?

Humphries93

Update, added constant 12v to PCM pin 3 and managed to get speedo, odo, and most likely tach signal, haven't confirmed tach yet. Still no grid heaters or ac, but this confirms that cps is good right?

maybe368

I don't know anything about the pcm or cps, but there are many on here that do. Try PMing Jmartin, he knows a lot about the electromics of these trucks, good luck...Mark

Humphries93

I will give him a shout, thank you!

torquefan

Do you have a diagram showing where the wire on pin 3 goes (or comes from)?

closefan

Sorry to bring this back, But I am at the same place as this first post. I have a 1993 W350 5-Speed,

No Odometer, No Speedometer, also, barebones so there is no AC no cruise etc.. I just checked and have constant power to PCM 3 and 9 and i assume grounds 11 and 12 are good because i did a resistance test?

Question? What does jumping 3 and 9 together do?

I dont have an AC so I cannot swap my ASD relays... But I think i checked power on that a while ago. Maybe issue lies there? Maybe need to buy a new ASD relay?

I dont get proper power to the Crank sensor. So I'm feeling its PCM? My alternator doesn't charge but thats simply because the CPS isn't getting power.

Checked my fusible links, they all seem fine.

No blown fuses either.

Any help you can provide, I would really appreciate.

Thanks,

Manny

ScubaSteveCA

Fusible links seem fine? As in they werent on fire or you checked them for continuity by poking holes in them with test leads?

closefan

I removed the stock coverings on each side of them and just went solder joint to solder joint testing for continuity. I also tugged on them a bunch after and re-tested. I assume testing for continuity is setting to resistance and 20k on the multimeter. I would get 0 between them.

j_martin

To check for continuity, use the lowest ohms setting on the meter, ie 200.

On the CPS, one pin is ground. One is 8V regulated from the PCM. The other toggles between about 5V and about 0.5V as the gap passes. I forget which way, but you can slowly rotate the crank and watch it with a meter. FYI, it.s a hall effect sensor.