What does the crankshaft position sensor do?
The crankshaft position sensor monitors the rotation of the crankshaft, specifically targeting when the number one piston reaches top dead center (TDC) in the cylinder. Most crankshaft sensors are mounted just above a notched ring on the crankshaft or above the flywheel. These sensors use a magnet to produce or vary an AC electronic signal that is used in conjunction with a camshaft position sensor to determine when a position approaches top dead center (TDC) on the compression stroke. In modern engines, with advances in variable valve timing and direct injection, the crankshaft position sensor is the most important input for the on board computer.
What are the symptoms of a faulty crankshaft position sensor?
Simply stated, the car will not run. Until the on board computer receives a signal from the crankshaft sensor, there will be no spark and the engine will not start. Moreover, when the on board computer receives an erratic signal, internal logic will understand this as a mechanical problem, and it will shut down the engine to prevent any damage. The engine will stall out for no apparent reason. Heat, age and especially rust are the biggest culprits for sensor failure.
What is the severity of a faulty crankshaft position sensor?
The failure of a crankshaft position sensor could leave you stranded on the side of the road waiting for the tow truck. Sometimes, if the sensor is allowed to cool off, the car may restart and run for a short period. Before getting to the turn and pray approach, find a good mechanic, one who specializes in engine performance, and set an appointment. Plan on dropping off the car for up to several days as some sensors make take longer than others depending on exact location.
What is the typical cost to replace a crankshaft position sensor?
- Estimated part(s) cost = $50- $100
- Estimated labor cost = $600- $700
- Estimated total cost = $650 - $800
This will be a repair of two extremes - cheap or expensive. The sensor will cost somewhere between $50 and $100 depending on the manufacturer. However, installation can really vary depending upon the car, and in some cases run upwards of $600 to $700 or more. Many sensors will mount on the engine or insert through a hole in the engine near the crankshaft pulley, which is much easy to access. Other sensors will mount inside the timing cover or inside the transmission bell housing, and are very hard to access. These parts will need to be removed in order to access the sensor. Incidentals, including gaskets, may run an extra $50 to $100 dollars.
Again, pricing will vary by location and your vehicle make and model. Save time and money by using Openbay to compare pricing and book an appointment with a service center in your area.
Service article written by an ASE Master Technician