The cam position sensor (CPS) on the 7.3L Power Stroke tells the computer engine position and speed. It is inexpensive, but when it fails it produces some of the most alarming symptoms on the truck: sudden stalling and no-starts that come and go.
What the CPS does
Mounted at the front of the engine, the CPS reads the crank/cam signal the PCM needs to time injection. Without a clean signal, the engine cannot run. The sensor is heat-sensitive, so a marginal unit often works cold and quits when hot.
Symptoms
- Engine stalls suddenly while driving, then restarts later
- Intermittent no-start, especially when hot
- Extended cranking before the engine catches
- Tachometer drops to zero right as the engine dies
Why owners carry a spare
Because the CPS is cheap, small, and can strand you without warning, many 7.3L owners keep a spare and the tools to swap it in the glovebox. A roadside CPS change takes only minutes. If your truck dies suddenly and the tach drops to zero as it stalls, the CPS is the first suspect.
Replacing it
Replacement is straightforward at the front of the engine. Use a quality sensor, since cheap units can fail again quickly. After installation, verify a steady start and confirm the stalling is gone through a hot-and-cold test drive.
Frequently asked questions
Can a CPS cause a no-start?
Yes. Without the cam/crank signal the PCM cannot time injection, so a failed CPS causes stalling and no-starts, often heat-related.
Should I carry a spare CPS?
Many 7.3L owners do, because the sensor is inexpensive, can fail without warning, and swaps in minutes on the roadside.
How do I know it is the CPS and not fuel?
A tach that drops to zero exactly as the engine stalls, plus heat-related no-starts, strongly points at the CPS.
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