This month’s winning tip reminds us that temperature matters. As featured in SearchAutoParts.com.
L. Scott Walker started his tech career back in 1992, after graduating from the St. Phillips College in San Antonio, Texas with an AAS degree in automotive technology. He started working at Mercedes Benz of Austin in 1999 and has been there ever since. In addition to fixing M-Bs, he is also an Adjunct Professor of Automotive Technology at the Austin Community College. While his tip is M-B related, it applies equally well to other makes.
“Sometimes a hot “no start” can be caused by a failure in the crankshaft position sensor (CKP), and not set any related trouble codes in the engine control module. The car will start and run fine after the sensor cools. I check the sensor by removing it from the car, attaching my ohmmeter, and then heat it up with a heat gun while watching the meter. If the sensor is bad, resistance will rise and possibly even go ‘open’.”
This tip applies not only to CKP sensors, but any electrical winding on the car like camshaft position sensors (CMP), EVAP purge valves and fuel injectors. You can test the latter by this method, or by activating them repeatedly with a scan tool or multimeter. (Learn more about using your DMM for bi-directional control)