Engine Electrical
Reference Sensor
A reference sensor reports crankshaft or camshaft position so the engine computer knows when to fire the plugs and injectors. We list 31 sensors from $13 to $170 by AC Delco, Standard Motor Products, SKP, Dorman and DIY Solutions, with strong coverage for Chevrolet Corvette plus Mazda Miata, Ram 2500 and Jeep Wrangler.
Shop reference sensor by vehicle
What the sensor does
The sensor reads a toothed wheel or notches on the crankshaft or camshaft. Each tooth passing the sensor creates a signal that tells the engine computer the exact position and speed of the engine. Without that signal, the computer cannot time spark or fuel. Some sensors listed here are also used in LS engine swaps, where matching the correct reluctor type matters.
Signs of a bad reference sensor
Common symptoms include an engine that cranks but will not start, stalling that often happens when the engine is hot and then restarts once it cools, intermittent misfires and a tachometer that drops to zero while driving. A check engine light with a crankshaft or camshaft position code is typical.
Damaged wiring, a loose connector or a worn reluctor ring can cause the same codes, so inspect those as well.
Choosing and installing
Check whether the sensor is for the crankshaft or camshaft and which side of the engine it mounts on. Some units include a wiring harness, with lengths such as 10.5 in or 15 in, and others plug straight in. Mounting brackets are not included on these sensors.
Oil the O-ring lightly before installing, and tighten the bolt to spec. Many GM engines need a crankshaft position variation relearn with a scan tool after replacement, or a misfire code may return.
Reference Sensor questions
Will a bad crankshaft sensor stop the engine from starting?
Often yes. If the computer receives no crankshaft signal, it cannot fire the plugs or injectors, so the engine cranks but will not start. A failing sensor can also cause stalling and intermittent no-starts.
What is a crankshaft position relearn?
It is a procedure done with a scan tool that lets the engine computer learn small variations in the reluctor wheel. Many GM vehicles need it after a sensor or engine repair so the misfire monitor works correctly.
Are crankshaft and camshaft sensors interchangeable?
Sometimes the same part number fits both locations, but often they differ. Order by position and check the fitment table for your engine.