cam position sensor irratic signal
 

Hi Fellas;
I picked up a 05. Was wrecked, not totaled and the owner didn't want to fix it, Red flag but hard to pass up. So I am finding the nagging problem.

Both codes trip for the cam position sensor and circuit. Had my regular shop check it out. First He said; the cam sensor was unplugged??? (I didn't think it would run but? it does) plugged it in and had an erratic signal, checked wiring, OK. He then installed the NAPA sensor I had bought and still the erratic signal.

So 2 bad sensors? or bad gear? It has signs of somebody being in the timing cover (116k mi.) So we are thinking somebody damaged the timing gear or its not timed right or the pickups are damaged???


Any Ideas?

Thanks Taggmann

The Camshaft Position Sensor (CMP) on the 5.9L diesel engine is located below the fuel injection pump. It is bolted to the back of the timing gear cover.
The Camshaft Position Sensor (CMP) contains a hall effect device. A rotating target wheel (tonewheel) for the CMP is located on the front timing gear. This hall effect device detects notches located on the tone-wheel. As the tonewheel rotates, the notches pass the tip of the CMP.
When the leading edge of the tonewheel notch passes the tip of the CMP, the following occurs: The interruption of magnetic field causes the voltage to switch high resulting in a signal of approximately 5 volts .
When the trailing edge of the tonewheel notch passes the tip of the CMP, the following occurs: The change of the magnetic field causes the signal voltage to switch low to 0 volts .
The CMP provides a signal to the Engine Control Module (ECM) at all times when the engine is running. The ECM uses the CMP information primarily on engine start-up. Once the engine is running, the ECM uses the CMP as a backup sensor for engine speed. The Crankshaft Position Sensor (CKP) is the primary engine speed indicator for the engine after the engine is running.
With the clip on the sensor pointed up, the far right terminal with the switch on should produce 5 volts, the middle pin should produce ground and the far left pin should show continuity to the 24 pin on the C1 ECM Connector. I would start with the basic wiring diagnoses to verify the wiring is correct.

Thanks for all the info. I will test those terminals.

Guess that would explain why it has to crank a while before it starts.

Since someone had been in the timing cover I am still suspicious about the tone wheel being damaged. Would the tone wheel damage easily?

Thanks again.

I would seriously doubt you've got damage of that magnitude and the truck still runs fine. The way i would determine, is A: Unplug the sensor and watch the cam PID and determine if it stays the same or changes (would indicate if the problem was on the sensor side or computer side) B:remove the sensor with the truck running and sensor still plugged up and determine what the PID does then.

I guess the better question is , are you saying there is a code indicating erratic signal, or is the PID erratic?

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On top of the items we've covered here's some items that can also cause CMP codes.

* Injector DTC's present
* Other DTC's
* Camshaft sensor
* (F855) 5-Volt supply circuit open
* (K916) Return circuit open
* (K44) Signal circuit shorted to ground
* (K44) Signal circuit shorted to supply (F855) circuit
* (K44) Signal circuit shorted to (K916) return circuit
* (K44) Signal circuit short to voltage
* ECM
* Intermittent condition