The Cam Position Sensor (CPS) on all 7.3L Powerstrokes can be its Achilles heel. This sensor tells the PCM where exactly the rotating mass is in its journey. Without it, or with one that isn’t working correctly, the PCM won’t know when each piston is nearing top dead center and therefore won’t be able to inject fuel into the combustion chamber at the right time. The CPS is hands down one of the most common fail items on the entire engine. If you’ve had a 7.3 for some time, you’ve likely either dealt with the CPS failing or it has already been replaced.

So how does the CPS work?

First off, it’s a Hall Effect sensor. Hall Effect sensors measure changes in a magnetic field. For the 7.3, a tone ring is mounted to the camshaft, this tone ring is made of metal and has gaps in it. The CPS is placed over the ring and as the ring spins, the sensor measures differences in the magnetic field as each of these gaps in the tone ring passes by. This is how the PCM gets its RPM and piston location information.

Why does it fail?

Long story short, it fails for many reasons, which all point back to it just being an inferior part. Aftermarket CPS’s failed the most, but Motorcraft and International parts, in the beginning at least, failed too.

Note: It's important to note that as these trucks grow in age, wire harness issues become more and more common. Harness/pigtail failures should always be considered when diagnosing a failed CPS concern.

What happens when it fails?

A failure of the CPS means the PCM isn’t seeing the information it expects to see. This can be intermittent data corruption or a lack of data from the CPS altogether. It’s worth noting that failure commonly happens on either end of the temperature range: hot or cold. So, at startup or after the truck has been running for some time. The most common issues when the engine is cold are hard starts, characterized by prolonged cranking, and complete no-starts. When the CPS fails while the engine is hot, it will commonly cause reduced power situations or rough running, but more often than not, the engine will just die unexpectedly. Cycling the key a few times and waiting a few minutes often allows for the engine to be started again, but it usually won’t run for very long after. Erratic tachometer readings are also a tell-tale sign of CPS failure. Because the CPS can fail intermittently or altogether, you may experience a mix of these issues.

What diagnostic trouble codes are commonly related?

•  P0340: Camshaft Position Sensor "A" Circuit Malfunction

This is the most common code. It indicates a general problem with the CPS circuit. This could be the sensor itself, the wiring, or even an issue with the PCM (though less common).

•  P0341: Camshaft Position Sensor "A" Circuit Range/Performance

This code suggests that the signal from the CPS is inconsistent or outside the expected operating range. It might be intermittent or inconsistent.

•  P0344: Camshaft Position Sensor "A" Circuit Intermittent

This code specifically points to an intermittent loss of signal from the CPS. This often manifests as the engine suddenly dying, then restarting after a few minutes, or experiencing random stutters while driving.

How do we fix a failed CPS? Simple.

We replace it. Assuming there are no other issues, like tone ring damage (rare) or wiring issues (common as these trucks grow in age), replacing the sensor with a quality one will fix the issue.

Which CPS replacement part is the best?

Over the years there have been a few different versions of the 7.3 CPS. Ones from Motorcraft or International are the most trusted. Here’s info on the most trusted three:

Black CPS (Original Design): The original black-bodied sensors (Ford part number F7TZ-12K073-A, or International equivalent), while they are respected for their signal output quality, these are the ones that had high failure rates.

Gray CPS (Later OEM/Recall Design): Ford later released a gray-bodied sensor (F4TZ-12K073-C, often associated with the recall Ford did around 2007-2008). While it fixed the stalling issue, many owners reported that these caused a miss at idle or other drivability concerns.

Dark Blue O-Ring (Improved Motorcraft International): Some International-branded sensors (e.g., part number 1876736C91) are black with a dark blue O-ring and are highly regarded for improved performance, smoother idle, and potential mileage gains due to a slightly different signal put out by the sensor.

 

For more in depth info on the CPS and it’s operation, check this out:

https://www.riffraffdiesel.com/content/RESOURCES/7.3L%20Cam%20Position%20Sensor%20.pdf

Related Parts Links:

Motorcraft Cam Position Sensor 1994-2003: https://www.riffraffdiesel.com/cam-position-sensor-cps-94-03/

Riffraff Diesel Cam Position Sensor 1994-2003: https://www.riffraffdiesel.com/cam-position-sensor-upgraded-cps-94-03-7-3l/

CPS Harness Pigtail 1994-2003 7.3 Powerstroke: https://www.riffraffdiesel.com/cps-harness-pigtail-94-03/

CPS O-ring 1994-2003: https://www.riffraffdiesel.com/cps-o-ring/