OK here goes….I do not believe that there is a simple and straight forward bench test to determine a faulty crank sensor. A bad crank sensor would be suspect if the engine cranks but doesn’t start and all other components of C3I system are OK, no code 41 or 42 is present and the fuel system is OK. I’ve also heard that a bad crank sensor can cause a loud backfire through the throttle body while cranking the engine.
As long as the sensor is not physically damaged it either works or it doesn’t. A misadjusted sensor or a bent interrupter ring would rub and damage the vanes on the sensor causing a rough idle, poor performance, or a no start condition. Clearance of 0.025” is required on either side of the interrupter ring. From the Buick shop manual, “ A crank sensor that is damaged due to mispositioning or a bent interrupter ring, can result in a hesitation, sag, stumble, or dieseling condition. To determine if the crank sensor is at fault, scan engine rpm while driving. An erratic display indicates that a proper reference pulse has not been received by the ECM, which may be the result of a malfunctioning crank sensor.” -Anthony P
