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How to properly diagnose this check engine code

Ronbrown77

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July 6, 2016
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City, State
Vallejo ca
Year, Model & Trim Level
1997 mercury mountaineer
Brought a 97 mercury mountaineer awd v8 and it came with a check engine light .the code is p0340 so what parts do I inspect to make sure its the camshaft sensor and not something else causing the PCM to say p0340
 






This is from OBD-Codes.com. It might help, but maybe not. At least you might get a better handle on the problem with more information. It looks like you are the right track with the Cam Pos Sensor but a problem could lie anywhere on that circuit.
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This diagnostic trouble code (DTC) is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model. So this engine code article applies to Nissan, Ford, Toyota, Chevrolet, Dodge, Honda, GMC, etc.
This P0340 code indicates that a problem was detected in the camshaft position sensor circuit.
Since it says circuit, that means the problem could lie in any part of the circuit - the sensor itself, the wiring, or the PCM. Don't just replace the CPS (camshaft position sensor) and think that will definitely fix it.
Symptoms
Symptoms can include:
Hard starting or no start
Rough running / misfiring
Loss of engine power
Causes
A code P0340 could mean one or more of the following has happened:
a wire or connector in the circuit could be grounded/shorted/broken
the camshaft position sensor may have failed
the PCM may have failed
there exists an open circuit
the crankshaft position sensor may have failed
Possible Solutions
With a P0340 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:
Visually inspect all the wiring and connectors in the circuit
Check for continuity in the circuit wiring
Check the operation (voltage) of the camshaft position sensor
Replace the camshaft position sensor as required
Check the crankshaft position circuit as well
Replace circuit wiring and/or connectors as required
Diagnose/replace the PCM as required
 






You can also remove the CPS and test it with a magnet and an VOM set to the continuity-beep setting. Hook up the VOM leads to the CPS's terminals, then you run the magnet over the tip of the CPS the VOM should beep indicating you have continuity. If it does your problem lies elsewhere (for example: bad/loose connector, broken wire, loose pin at the PCM. I've also read that a problem with the alternator can mess with the CPS signal).

As an analogy, lets say you have a table lamp that suddenly stops working. You can assume the problem is the bulb, but if you change the bulb and the lamp still doesn't work the problem may be in the socket, the wire, the plug, or even a tripped circuit breaker. If a light bulbs cost $40 it's best to determine where the real problem is before buying one. Also keep in mind that electrical components usually cannot be returned.

A VOM (volt ohm meter) is an essential tool to have when working with electrical components in your home and your vehicle. A decent one will run you some money, but it will pay for itself very quickly. Many under-hood sensors have an electrical range that they must operate within. When they fall out of their specified range the check engine light gets turned on by the PCM. Having a VOM and knowing the operating range of a sensor will allow you to test all your vehicles sensors, your wiring, your alternator and to some extent your battery.
 












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