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1st Gen. Ram - All TopicsDiscussion for all Dodge Rams prior to 1994. This includes engine, drivetrain and non-drivetrain discussions. Anything prior to 1994 should go in here.
Yes the PCM is behind the battery tray on the '91.5-'93 trucks.
They move it to the passenger firewall from '94-'02. Newer trucks than that I have no interest in, so I don't know what happens after '02.
I have no dealings with Mymoparparts, so I have no idea what they do, what they sell, or what they call things.
Yes the PCM is behind the battery tray on the '91.5-'93 trucks.
They move it to the passenger firewall from '94-'02. Newer trucks than that I have no interest in, so I don't know what happens after '02.
I have no dealings with Mymoparparts, so I have no idea what they do, what they sell, or what they call things.
I have both. Did someone try to put a later year computer in the truck?
I posted this to a thread in 2017; it's still relevant:
Originally Posted by james1
I'm dreadful with electrical problem diagnoses, but my unscientific observation from reading this forum for several years is that most issues blamed on the PCM turn out to be the fault of a different (and less expensive) part.
A couple of years ago my Crankshaft Position Sensor began failing intermittently and, when it failed, the truck would quit charging, OD would turn off, and the air conditioning wouldn't work. I replaced the CPS and solved the problem but when I was wrapping the wires on the old unit to discard it I realized there was a small piece of metallic debris stuck to the face. (The CPS is magnetic.) So my guess is I could have cured the problem by simply cleaning the debris off the face of the CPS.
And when this whole issue started, I too blamed the PCM...
I started looking at the crank sensor. Any idea how to test it without tearing the whole truck apart. I seen the wire leading down to it but can’t find the actual sensor itself. I also can’t seem to figure out to to test the voltage on the different wires. Unlike with the tps where you can pull out the dust plug and check everything at the sensor, the crank sensor plug is sealed. Also how to I test the sensor gap?
Can anyone tell me if this “jump” is factory. Turned on the ac and it DID NOT kick on, which leads me to believe the crank sensor is bad. Is this the previous owners way of trying to get the ac to work?
I started looking at the crank sensor. Any idea how to test it without tearing the whole truck apart. I seen the wire leading down to it but can’t find the actual sensor itself. I also can’t seem to figure out to to test the voltage on the different wires. Unlike with the tps where you can pull out the dust plug and check everything at the sensor, the crank sensor plug is sealed. Also how to I test the sensor gap?
Either back probe the connector (push a sharp probe in beside the seal on each wire) or pierce the wire near the connector. I prefer the second, but be sure you bandage the wound with a drop of liquid electrical tape. (vinyl in solvent) to prevent corrosion and future failure.
As I said before, verify ground and 8V are present, then probe the third one and watch it toggle as you turn the gap slowly past the sensor. The gap in in the harmonic ballancer, and the sensor is bolted just above it, on the end of the 3 conductor cable to the connector on top of the engine at the front.
Sensor gap is critical, and magnetic debris on the sensor will cause trouble as well.
Can anyone tell me if this “jump” is factory. Turned on the ac and it DID NOT kick on, which leads me to believe the crank sensor is bad. Is this the previous owners way of trying to get the ac to work?
That's a diode to drain off the solenoid coil's back emf when the circuit is opened, protecting relay contacts or electronics. It's stock.
Either back probe the connector (push a sharp probe in beside the seal on each wire) or pierce the wire near the connector. I prefer the second, but be sure you bandage the wound with a drop of liquid electrical tape. (vinyl in solvent) to prevent corrosion and future failure.
As I said before, verify ground and 8V are present, then probe the third one and watch it toggle as you turn the gap slowly past the sensor. The gap in in the harmonic ballancer, and the sensor is bolted just above it, on the end of the 3 conductor cable to the connector on top of the engine at the front.
Sensor gap is critical, and magnetic debris on the sensor will cause trouble as well.
Do you happen to know what the gap is supposed to be set at? I read 50 thousandths on another forum, but that seems like a awful lot. Mine is set anywhere from 25 to 30 thousandths depending on where the crank is positioned when I test it.
05-07-2019 | 06:12 PM
