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Dodge Repair/Cam Shaft position sensor frequent failure: 4.7L


QUESTION: I have a 2002 Dodge Ram 1500 4x4 4.7 v8.  It a reman motor.  the problem we are having is it keeps throwing a code for the cam shaft position sensor all mechanics that have looked at it say there is nothing wrong with the motor it the sensor.  We have had three of them in less than 2 years.  We also replaced the the pig tail for the sensor.  Is there anything that would cause this to happen?

ANSWER: Hi Larrie,
If the replacement of the sensor each time immediately solves the problem for a while then it would appear that the sensors are failing prematurely. I would doubt then that it has anything to do with the electrical connections of the sensor to the engine control module, but certainly the mechanics should have checked the continuity of the three wires that are involved in the sensor circuit.
So the other possibilities are that the sensor may be failing due to excessive heat, or that there is a problem with the engine control module (though it would be strange that replacing the sensor solves the problem immediately, were that the case).
So I wonder whether the engine may be running excessively hot due to an issue with the thermostat or the cooling system. The sensor is mounted directly on the side of the right cylinder head near the front which is no doubt a very hot location ( from the cylinder head itself and the nearby radiator). So consider how the temp gauge is reading most of the time. Is it running hot quite often? Dose the failure occur, and then when the engine cools does it run normally? That would corroborate the idea of overheating of the sensor.
You might want to fashion some sort of metal 'fins' to attach to the sensor to improve the cooling of it.
Those are my thoughts.
Please read the PS below and respond to it.

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QUESTION: The truck is not running hot according to the gauge in the truck and surely one of the mechanics that has had it would notice if it was getting hot.  What it does is it will run good for several months and then it will start going into limp mode is what the mechanics say.  It will let me drive it around 50mph no problem and no faster.

ANSWER: Hi Larrie,
"Limp-in mode" is a term often applied to the electronic automatic transmissions, and has nothing to do with the camshaft position sensor. The trans will only drive in 2nd gear while in that "mode".
So which is it? If the fault code is P0340 then that is the cam shaft sensor, if you get a P0700 then that means there is a transmission problem. Turn the key;"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage replaced by a 4-digit number preceded by a P.
As to the possible short lived cam sensor, all I can suggest is that it is being damaged by heat. Most engines don't mount that sensor on cylinder head proper so that is why I suggest that is the possible cause. Again, try to add a 'cooling fin' of some sort and see if that helps.
Please read the PS below and respond to it.

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QUESTION: Ok got some more info.  They have changed out the sensor and pigtail that is located on the back passenger side of the truck.  Now they have changed out the sensor on the front of the engine I believe one is the crank shaft position sensor and the other is the cam shaft position sensor. They say they have both been changed out twice now. Ran great for them they say, I took it now showing codes I read with a reader Codes 725, 320, 300, 302, 305.  These have shown up since the first time we had the truck worked on after they redid the engine.  If you run the engine it runs bad and if it dies it wont start unless you remove the battery cable and then it will start but still runs bad.  At this point don't know what to do.  Do I put in more money or run for the hills.  When truck does run right it runs good but it does not run right very often.

Hi Larrie,
Were those codes you listed definitely current codes, or might they have been 'stale'. If you or the shop didn't disconnect the battery recently to erase stale codes then I would do that now and then look for 'fresh' codes after driving it some more.
The 300 level codes are about engine missing on cylinders 2 and 5, the 320 code says the crank shaft position sensor signal is poor/missing, and the 725 is also about the crank signal not giving a good indication of the engine rotational speed (rpm). So if the codes are still there it indicates either that the crank sensor or its three wire circuit is compromised or possibly that the engine or transmission control module is malfunctioning (those are expensive items and would not be replaced absent some further codes suggesting which one is bad).
So try to get some 'fresh' codes and let me know what they are.

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Roland Finston


Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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