my mom complained her cars check engine light had been on in her 2000 pontiac bonneville. she said it had been idling rough and stalled (restarted in neutral)while driving once or twice the past few weeks. my scanner showed 3 codes which turned out to be knock sensor bank 1 and 2. and crank sensor. i changed the crank sensor and now the car wont start at all.....just cranks. does this sound like i got a bad sensor?

Bad sensor or possibly timing is off by a few degrees?

You will need to check for spark. If no spark, the check the crank sensor. If you have spark, then check fuel pressure.

Ensure the connector for the crank sensor went in all the way and no pins bent. The part may be DOA.

there is also a crankshaft variation learn procedure called a CASE learn that sometimes needs to be done for the pcm to learn the position of the crank. (not common on a sensor change though).

im pulling the pulley back off after class tonight.....i read up on the learn procedure but it requires the vehicle to run first...........also i couldnt have changed the timing by pulling the crank pulley off could i???? the car ran before id just hate to change it again and have the sane results....can i use an ohms meter to test it or is poking into wires a bad idea here?

Test the sensor with a ohm meter. As you turn the engine over it will change. It should go up and down as each blade goes past the sensor. I agree with Bill, check the plug first. Then check the ohms. If no reading, the sensor may be to far from the blades.

pulled it all apart to inspect and didnt notice anything accept that the metal flanges the sensor uses were dirty....i cleaned them and reinstalled and now it runs great. how do the crank sensors work exactly, i thought it was magnetic? hard to believe the dirt would do that

The magnetic field is interuppted by the fin of the HB passing by. Not sure what dirt has to do with it. But I've been there, had that same issue.

More likely you were out of adjustment.

On an unadjustable sensor??????