I have a 98 Jimmy 4.3 with a rebuilt engine that won't start. Scan tool reads crank shaft position sensor. Change it with my 99, same problem. Went to Autozone and picked up a new one, same problem. The truck cranks, but will not fire, has fuel and spark with 12volts. Traced the wires from the sensor, no problems there. Can someone please help me?

 

If the PCM is not seeing the CKP sensor, it will not start. It is quite obvious that you have a problem with the sensor and/or the wiring. Does the sensor have power? Good ground? Have you monitored the sensor output at the sensor and again at the PCM to ensure that they are both reading the same at both ends?

 

Yes, the sensor does have power. How do I monitor them? ohms, continuity, volts

 

Any codes?

As far as how to monitor them, I would start with a capable scan tool. But without that, I believe you should see ~0.5V-AC when the engine is cranked over between the sensor return and the sensor ground wires.

 

Thanks, I'll try that. The wires I traced from the crank sensor went one to the fuse box. The other two went to the computer. No ground wires!

 

The ground is one of the two wires to the PCM. That is how the PCM detects faults within the sensor.