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Distributorless ignition systems require a crankshaft position sensor (CKP), and sometimes also a camshaft position sensor (CMP). These sensors serve essentially the same purpose as the ignition pickup and trigger wheel in an electronic distributor, the only difference being that the basic timing signal is read off the crankshaft or harmonic balancer instead of the distributor shaft. This eliminates ignition timing variations that can result from wear and backlash in the timing chain and distributor gear. It also does away timing adjustments (or misadjustments as the case may be).
On 1996 vehicles with Onboard Diagnostics II (OBD II), the crankshaft position sensor is also used to detect variations in crank speed caused by ignition misfire. If the computer senses enough of these, it will illuminate or flash the Check Engine or Service Engine Soon light to signal the driver he has a problem
Hope this helps you understand the functions of the crankshaft position and camshaft position sensors a little better!
Thursday, January 21st, 2010 AT 5:50 PM