Does anyone know how to test the CPS for voltage/resistance while on the car and what should the correct readings be? I read that you should just measure the ohms between the red and blue wires and that while still connected to the same wires switch the multimeter over to AC Volts and take that reading while cranking the engine. Is this correct and what should the readings be? I'm trying to track down a no spark issue. Also not getting any kind of readings from the tachometer while cranking. Is this a definate effect from a bad crank sensor or could the ECM be the cause?

 

I believe the nominal DC resistance across the CPS terminals is given in the AJ6 Engine Management System manual, which you can download from jagrepair.com. The manual may be in the XJ6 & XJ12 section rather than the XJ40 section.

To read the sensor's output signal you would probably need a scope. The actual pulsed current is probably not a true AC since its polarity doesn't alternate, and its magnitude may be too low for most multimeters meters to measure reliably, but it would sure be worth a try.

The 0 RPM on your tach is a classic sign of either CPS failure or a problem in the electrical harness, usually right at the connector.

Cheers,

Don