No Spark, Crankshaft Position Sensor Testing


New Member
Virginia City
United States
What I Drive
1994 Ranger XLT 4x4
My son’s1994 Ranger 4x4 V6 4.0 had blown head gaskets which we replaced. The truck is back together and cranks over fine, and has fuel pressure on the rails, but, there is no spark. We think it’s the crankshaft position sensor, but I’m finding conflicting info on how to test it. Here’s what I’ve done. First, I’ve watched the tachometer while cranking the engine (while connected to a battery charger in boost mode so we have plenty of cranking power). I would expect the tach to jump around a bit, or even go to 100-200 rpms while cranking, but it just sits flat, no movement at all. That implies the CKP sensor isn’t sending a pulse to the PCM. So I then crawled under the front and disconnected the 2-wire connector to the CKP sensor. I think one line should be hot and one ground in KOEO, but they both show about 1.5vdc in KOEO (maybe shorted together?).

The CKP is a Hall Effect sensor and as I understand it it should put out AC pulses when working properly. On the bench, when I connect my Fluke DMM to the pins and move a large bolt back and forth over the sensor pin I get reading pulses of between 0.02-0.05 volts AC. So a couple of questions...

Should the two wire lead have a reference voltage on one lead and a ground connection in the other? I don’t think they should both show 1.5vdc reading in KOEO. So what should these 2 wires read?

And what is a proper voltage reading when passing a metal object over the sensor while testing?

One other thing. One of my manuals says I should get a resistance reading of between 200 ohms and 2000 ohms between the pins on the sensor, and a different manual says not to ohm out the pins as the passed voltage could damage the sensor coils. I tested resistance before I saw the “don’t do it” manual recommendation, and got no resistance reading at all on my Fluke DMM. Should there be resistance or not, and did I jack it up by trying to test it that way? I still get the AC pulses, even after testing the resistance, so I assume it’s working, but what do I know! Help,