2005 Century 3.1L start no run -after Crank Position Sensor replacement

[Dan Hoover]

Wife's car left her stranded for first time. I found a crank-no spark-coils check ok,no codes though,seen this on my previous car-thought "cps". Trailered the unit 2hrs home picking up a CPS(the ugly one in the back side of the block). Checked the car again at home-same.
Changed cps-no change-checked wiring and sure enough an open connection at the sensor end. Repair the fault, now car has spark and 50psi fuel pressure will start and run a few (3?)seconds and die.

Did a key relearn-no dice. Did a resistor bypass-no change,verified the security by intentionally altering the R value-yes tdm locks the car out. So removed bat cables for a day, checked the injectors for a short- none found-seem all same around 24 ohms. did the security relearn and back to square one, Start-run 3seconds die. The car will run indefinitely on starter fluid sprayed into the intake so it is definitely fuel cut off. Wish I had a real scan tool but that is not the case. Nearly lost my patience with this one.Any suggestions would be greatly appreciated. Gut feeling is bad bcm, please tell me I'm wrong.
(much of the diagnostic procedure was thanks to threads on this site-thanks for all the good information, I learned a lot)

 

[NFortin198]

I would check the cam position sensor as this tends to short out at the point where the wires enter the sensor. It is located on the top front of the engine block just in front of the lower intake manifold. You also have a second crank position sensor located behind the harmonic balancer. Crank position sensors may not relearn by the key method in which case it must be done by the dealer, but that is usually only for the front sensor.

 

[Dan Hoover]

Thanks very much for the reply I will do.

 

[Dan Hoover]

Update, must not have been doing the relearn correctly? as after finding nothing wrong with the wiring, I left the battery unhooked overnight. Came back the next day, drained fuel tank,(nothing found in that avenue) put in some fresh fuel, hooked up battery and did the 30min security relearn. Car started first flip and has been working perfect since. I think I was not doing the procedure properly before. Key must be turned forward just to -On-not to engage start- to begin sequence. Didn't cost much to fix this but sure spent a lot of time to understand this system. Thanks to all those that help us amateurs, we do appreciate it.