Q: How to diagnose and replace a crankshaft position sensor on Ford Explorer Sport Trac?
A: If the following tests indicate that a sensor is good, and not the cause of a driveability problem or OTC, check the wiring harness and connectors between the sensor and the PCM for an open or short circuit. If no problems are found, have the vehicle checked by a dealer service department or other qualified repair shop. The crankshaft position CKP) sensor is mounted on the engine front cover, next to a toothed trigger wheel. The trigger wheel has 35 evenly spaced teeth and one gap where a 36th tooth would be. The gap lets the CKP sensor signal the PCM when the crankshaft is 60-degrees before TDC for cylinders 1 and 5. The PCM then computes actual TDC or any number of degrees before or after TDC and uses this information to control ignition spark advance. The CKP sensor also provides the engine speed signal to the PCM and is part of the misfire monitor circuit integrated into the PCM. The Electronic Engine Control (EEC)system can detect different CKP sensor problems and set a trouble code to indicate the specific fault. Disconnect the CKP sensor connector, turn the ignition On but do not start the engine. Use a voltmeter to check for voltage between the sensor connector and ground. Disable the fuel system, connect a voltmeter to the CKP sensor, set the meter on the AC scale, and check for voltage pulses as you crank the engine. Caution: Keep voltmeter leads away circuit voltage at the sensor connector should from the drivebelt and rotating engine parts while cranking the engine. If no pulsing voltage signal is produced, replace the crankshaft sensor. Be sure the ignition is off and disconnect the sensor electrical connector. Remove the retaining bolts and remove the sensor from the engine front cover. Installation is the reverse of removal. Note: On 2001 and later models, if you are replacing the CKP sensor, the new sensor will have small wear tabs at the crank pulley side. Install the sensor with the spacer tabs touching the damper, then tighten the mounting bolt(s). Once the engine is running, the tabs will quickly wear off, leaving the correct sensor-to-puller spacing.