Saab Crankshaft Position Sensor - Bosch 12789959

Product Information

The engine crankshaft position sensor monitors the position and rotational speed of the crankshaft, providing information to the engine control unit (ECU). The sensor ensures proper timing for fuel injection, ignition, and other key engine functions. Without accurate crankshaft data, the ECU can't adequately time the spark or fuel, causing poor performance or even preventing the engine from running. Crankshaft position sensors come in different designs, with magnetic or Hall-effect sensors being the most common. The magnetic sensor consists of a coil and magnet that generates a signal as the engine rotates, while the Hall-effect sensor uses a semiconductor to detect changes in the magnetic field.

The crankshaft position sensor is usually located near the crankshaft pulley/harmonic balancer, or flywheel/transmission depending on the engine’s design. It works by detecting notches or teeth on a component called a reluctor or tone wheel, creating a signal that the ECU can interpret. When this sensor fails, common symptoms include engine stalling, rough idling, misfires, or the engine not starting at all. One of the most frequent failure modes is internal short-circuiting due to heat and vibration over time. Contaminants like oil, dirt, or metal shavings can also interfere with its ability to detect the crankshaft's position.

• No Start Condition: The CPS gives the information to the ECU that the engine is showing positive RPM and is ready to start. If the computer does not get a signal from the sensor, or the sensor is outputting values that it is not anticipating, the engine won’t start.
• Stalling when warm: Once the engine warms up, a failing crankshaft position sensor can often cause stalling when coming to a stop because the engine doesn’t have the right information to maintain a stable idle.
• Dead or erratic tachometer: Some older vehicles may run the tachometer off of the output from the crankshaft sensor. If the tach is behaving strangely, especially in conjunction with other running problems, the CPS could be at fault.
• P0335: If the integrity of the internal wiring has failed, you may get a P0335, however it is not a guarantee that a vehicle with a failing CPS will have a check engine light.
• Poor performance at certain RPMs: A failing crankshaft position sensor can cause issues with engine performance, especially if at a certain point in the rpm range the sensor can’t send an in-range signal to the ECU with may cause timing to drift. Failing crank position sensors more commonly cause running issues at higher RPMs and idle.
• Misfires across multiple cylinders: If the engine is struggling to time fuel and spark, you may encounter misfires across all cylinders at once. This is in contrast to the failure of a coil or fuel injector, which may only effect one cylinder at a time.

About Bosch

Bosch is one of the worlds leading suppliers of engine electronics and sensors. Their sensors and modules can be found in almost every modern car on the planet. Bosch Automotive offers a comprehensive portfolio of unmatched solutions for every job. From diverse diagnostic solutions and OE-quality auto parts, to industry-leading software and unmatched vehicle coverage, to innovative charging, repair and maintenance tools. Making repair and maintenance more effective, efficient, and sustainable for the vehicles of yesterday, today and tomorrow. With over 130 years of experience in the automotive industry, Bosch continues to lead the way in automotive innovation by inventing and developing quality products and solutions that focus on customer needs, shaping the future, and the continued pursuit of excellence.

Robert Bosch founded the “Workshop for Precision Mechanics and Electrical Engineering” in Stuttgart, Germany in 1886. Since the beginning Bosch has been a leader in innovation and development. They introduced fuel injection into mass production in 1967 laying the foundation for modern ignition electronics. Bosch brought lambda sensors to market in 1976, paving the way for cleaner exhaust gases and better fuel economy.

With millions of parts and products in their product line, Bosch offers everything from brake pads to household tools and medical supplies. FCP Euro has partnered with Bosch for the 2019 TC America Championship. They are a sponsor on our 2018 Volkswagen GTI TCR race cars. We offer Bosch's full line of OE and OEM components for your European vehicle.