Where is the Crank sensor on 1999 blazer 4.3?

If you want to do it yourself procure the Haynes Manual for your unit. Part number 24046 '90-94.: There may be a couple of sensors, the procedure below is for the 24x sensor if fitted. remove the drive belt. raise the car and support on jackstands remove the crankshaft pulley remove the bolt and the sensor wiring harness bracket. Note well the routing of the wiring as you must replace it as installed at the factory. remove the sensor mounting bolts and pull the wiring harness. reverse the procedure to install. After disturbing the seensor the crankshaft variation relearn procedure may be required. If the engine MIL light illuminates take it to a dealer and get them to reset the system for you. To replace the 7x sensor, disconnect the wire, remove the bolt holding the sensor in th eblock and withdraw the sensor. make sure you replace the O-ring after lubing it with engine oil.