O.K. so my 03 4.0 4x4 has some issues. It IS a 22 year old truck, so its expected. Oil change, replaced some lamps, did a u-joint in the front drive shaft. Spedometer was inoperable, fuses all good, popped a new spedo into the cluster, still not working. I went and got a better scan tool, PCM didn't have the speed signal, so I replaced the VSS. The old one was new, but unsecured, and looked a little chewed up. PCM had a signal now, but the spedometer was still dead, did i put a bad one back in? A few days later, i filled the tank, and shortly after, the the engine ran rough, and died, will not restart, will not turn over. Check engine light is off, theft light is on with a slow blink, i can access different modules via the OBD port, the anti theft module has no dtc. I checked all the fuses via multi meter, all good. When i turn the ignition key i can hear a relay pop, just nothing else. I know I am going to be chasing wires around, where would be the best place to start?

 

Also, someone before me completely trashed the vacuum system. No vacuum to the blend doors. The valve covers are dammaged and leaking. Should i just start a restoration/ repair blog on this truck? Body is in so-so shape, a few chips and a few deep scratches. Fenders have significant dents, so i ordered a new pair from painted parts. Put on a new pair of 265/75R16 AT tires. Replaced the dome light assembly, also replaced the 3rd brake light assembly. Replaced 3 light sockets, and had to repair 2 of the light wiring harnesses.

 

So. Did some "wiggle" tests. All the major harnesses. Removed the pcm harness cleaned the connector, checked the pcm connector, there was a bent pin, pulled and straitened it. I doubt that is the issue, considering, but it might be why the speedo wasnt reading. Went ahead and put down some dielectric grease, reconnected, with no joy.

 

I didnt have much time today to tinker with the Ranger. I did, however, find that the PCM diode was open both ways. Theres battery voltage at the pcm relay. The relay is good. I will get a new diode tomorrow, but it is looking like the pcm is bad.
was scrolling the forums and member Ron_d had this bit of wisdom in another post:


Theft light flashing mean PCM is partially working.

Theft light should stop flashing if PCM is booting up

A few wires you can test, red wire on coil pack should have 12v with key on, same 12v PCM gets

Throttle position sensor has Brown/white wire, it should have 5volts from PCM, that means PCM is getting startup voltage

Im my case i have 12 volts at the coil pack, and .4 volts at the tps.