Camshaft Position Sensor Circuit

[kg49erfan]

I just received a 1997 Ford Taurus GL from a family member. The Service Engine Soon light is on and the State of CA will not smog it until it is fixed. When I hook it up to a machine to diagnose the problem I get the following: Code 340, Camshaft Position Sensor Circuit Malfunction. Is this an easy fix or am I talking thousands of dollars? Also, if it is an easy fix, can I do it myself? Any information will be greatly appreciated. Thanks.

[hughw]

The cam spostion sensor is located on top of engine on the transimssion end of the engine..You can see a wiring harness mostly covered by a plastic sheild....The cam position sensor is right under this wiring.
The sensor part will cost about $35......and thats probably all you will need....if the shaft and gear assembly is needed...I think I saw where it is around $250.........Even if you had it done in a shop, It would probably not be cost prohibitive if the car is ok otherwise.

[kg49erfan]

Originally Posted by hughw

The cam spostion sensor is located on top of engine on the transimssion end of the engine..You can see a wiring harness mostly covered by a plastic sheild....The cam position sensor is right under this wiring.
The sensor part will cost about $35......and thats probably all you will need....if the shaft and gear assembly is needed...I think I saw where it is around $250.........Even if you had it done in a shop, It would probably not be cost prohibitive if the car is ok otherwise.

Thank you for the information. I think only the sensor needs replacing so that is what I will do first. I will let you know if that works. Thanks again.

[ronaldomckay]

I have a 2001 Taurus I purchased the cam shaft sensor right from the dealer. It cost less than 50 dollars and I installed it myself...then cleared the trouble code. Car has worked great since then.

[TomV]

If it is only the Sensor that is bad then the effort is something a normal home mechanic can do, provding you have a very small (5 mm or so) socket to remove the two screws holding it to the Synchronizer. The unit is located under the throttle cable assembly on top of the engine, beneath a pain in the ass plastic wire harness. I had to break the plastic harness to get to the Sensor. However it is an easy component to remove and replace once the components over it are removed.

That is the easy part. If the damage also includes the Sychronizer then more money is involved since it cost me around $160 from Ford. I have performed this repair myself and was able to do it in an easier fashion than indicated in both Ford and Haynes manuals. However this was because the vane in the Synchronizer was intact (though deformed) and I could determine its position relative to holes in the assembly and transfer that information to the replacement unit. This avoids the complex alignment procedure necessary when the previous alignment position is not known. You will not know if the Synchronizer is bad unless you remove the Sensor and perform a visual inspection.

The Haynes manual, available at your typical auto parts store, shows the assembly is located on top of the engine, underneath the spark plug wires 1,2 and 3, that are routed to the rear of the engine. You need to take off a few parts, such as an air hose, some electrical connectors, throttle cable assembly, plug wire routing harness and such. It is not too time consuming once you see the book and the sensor's location. You need the proper size wrenches. There is a flat, rectangular, plastic wire harness directly over the sensor that does not come off. I bent it around a bit and it cracked some, but not enough to cause any real damage. It does allow the overhead access needed to remove the plastic sensor from its housing. You need some small socket wrenches for this. I just bought a set of small sockets, metric and English, for stuff like this. An extension shaft of at least 6 inches is very useful here.
Once the sensor is removed (2 screws and electrical connector) you can view the rotating shaft in the synchronizer housing to determine the condition of the semicircle vane that rotates through the magnetic field of the sensor. Check the sensor for damage too. The magnet in the center of mine was snapped off and caused the vane to be bent inwards. If you do not see any damage to the metal within the housing then just replace the plastic sensor and see if that solves your engine light problem. Blow out any loose parts before assembly. If there is noticable damage to the metal within the housing then you need a new synchronizer. I paid about $30-35 for the plastic sensor (Autozone) and $159 (Ford dealership) for the metal synchronizer assembly. But I paid no labor. The job takes about an hour if only the plastic sensor is bad and about 2 hours if the synchronizer is faulty and you use the following procedure to properly align the system. It may also give you an excuse to buy some small socket and box wrenches as well! If replacing only the sensor does not eliminate the engine light then you could have a faulty synchronizer (gear not meshing properly) or an electrical problem between the sensor and the computer.

The tool used synchronize the system in the fashion described in the Haynes and Ford documentation (I have a copy of each) assumes that the #1 cylinder is at TDC. It aligns the vane of the rotating shaft relative to the magnetic circuit of the CMP Sensor. The vane disrupts the magnetic field as it rotates and the signal is sent to the computer. The 38 degree setting of the housing is not necessary for the synchronizing aspect but for assuring the electrical connector can be placed on the sensor since it is a fairly short cable.
The rotating shaft can fit in any one of 14 positions (14 teeth on the gear). It does not fit only one way, and is not polarized. I was also able to place the assembly in more than two different positions myself. Therefore, if you want to replace this assembly without the use of the tool and the setting of the #1 cylinder to TDC as described by Ford, you must record the position of the shaft's vane prior to its removal, relative to the housing. This is similar to using the synchronizing tool, but with the postion of the cylinders in an intermediate state.
After taking the plastic CMP sensor off, I transferred the position of the vane onto the top surface of the housing rim with a Sharpie fine tipped pen. The vane was bent out of shape from the magnet that fell from the sensor, but the edges were still in place. I then transferred a mark to the manifold across from one of the three small gaps in the housing rim, the one opposite the large gap for the electrical connector. This would ensure that housing is placed back to its original position and there would be no problem getting the electrical connector back on.
The entire assembly is removed with the removal of the single screw on the engine block. The shaft rotates CCW on removal.
Transfer the marks on the old assembly onto the replacement assembly. Oil the shaft thoroughly. Place the unit into the engine, inserting the shaft onto a pin in the engine. The vane should be rotated CW as it is pushed down. Once the assembly is against the engine, check the alignment marks for the vane/housing and housing/manifold. If necessary, pull up the unit and reinsert it in another position until the alignment marks correct. Now you can replace the hold-down screw and its fork/washer to keep the housing in place.