Crank Sensor Working Theory
The crank sensor (it's full technical name: crankshaft position sensor) senses the exact position of the crankshaft and sends this info to your vehicle's fuel injection computer (whose real technical name is: Powertrain Control Module -PCM).
This info helps the computer calculate the correct time to fire the spark plugs, pulse the fuel injectors, advance or retard timing, keep the fuel pump activated (among a few things).
The crankshaft position sensor, on your Chrysler 2.7L, 3.3L, or 3.5L equipped car, is a Hall-Effect three wire crankshaft position sensor. What this means: it produces an On/Off DC voltage signal that can be easily measured with a multimeter, an Oscilloscope, and even an LED Light.
Each one of the three wires that connect to it have a specific job to do:
- The wire labeled with the number 3 delivers power in the form of 5 or 8 Volts from the PCM.
- The wire labeled with the number 2 delivers ground. This ground is provided inside the PCM, too.
- The wire labeled with the number 1 delivers the signal, that the crank sensor creates, to the PCM.
The most important thing to know, is that if the crank sensor goes BAD, your Chrysler (or Dodge or Plymouth or Eagle) vehicle will Crank but Not Start.
You'll also see the following symptoms:
- No spark from any of the COP ignition coils.
- No fuel injector pulses (as tested with a fuel injector noid light).
- ASD relay doesn't stay activated beyond the initial 5 to 10 seconds the engine is being cranked by the starter motor.
Related Test Articles
I have written quite a bit about the 3.3L, 3.5L Ignition Systems. You can find a complete list of all of these articles here: Chrysler 2.7L, 3.3L, 3.5L, 3.8L Index of Articles.
Here's a small sample of the articles you'll find in the index:
- How To Troubleshoot A Misfire (Chrysler 2.7L, 3.2L, 3.5L).
- How To Test Diagnostic Trouble Code P0750 (Low Reverse Shift Solenoid Malfunction).