There are times that take a lot of the fun out of running a shop, and this 2004 Dodge Neon is a good example of that.  About four months ago the car showed up and it was setting a P0344 for a camshaft sensor signal sync error. The scan data at that time showed the camshaft signal missing, and measuring the signal in between the sensor and the PCM confirmed that it was inoperative because of the presence of the five volt reference that comes from the PCM that the sensor pulls to ground when it turns on. The sensor is a Hall Effect design that turns on when a magnet that is attached to the back of the camshaft passes close to it.  The last two checks for the power to the sensor and the ground circuit showed that the power and ground were correct so replacement of the sensor and it’s pigtail connector was indicated. The repair was completed, the code cleared and the vehicle was road tested with no other troubles found.

Monday afternoon the customer calls and reports the same symptoms of surging over 2100rpm and the check engine light is on again. We told him to bring it right down and when he showed up it was working just fine again. Pulling the code the P0344 was set in the history and scan data showed “cam lost last”. At this point there wasn’t much else to do but run the customer home and set up my testing connections to prove where the fault was occurring at.  The car ran fine the whole way to his home and back down to the shop. Leaving it run in the shop with my wife paying attention to it, the circuit failed at some point because the light was on and scan data showed sync  lost, but the signal was fine on the oscilloscope.

Several start and run routines were then performed over the next day and no trouble was identified. When attempting to diagnose a problem like this the only thing that really works consistently when trying to solve them is a good plan and a lot of patience. Many would resort to throwing a camshaft sensor at it and ship it out the door, and of course there is a chance they might be successful. The problem with that approach goes hand in hand with something the customer said during this phase of the testing. He was already losing confidence in the car and started lamenting the idea of replacing it. If a tech guesses and gets it right, the symptom may go away but the customer really has no reason to believe that the car is really repaired and it could act up on him at any time and then he would fear being stranded. The only way to restore his confidence in the vehicle is to be certain that the problem is found. Since leaving it run in the shop wasn’t giving me the information that I needed, the next step is to go on a suicide mission and drive the car and diagnose it when-ever and where-ever the problem occurs. So with the scan tool and the PICO four channel scope connected to the critical circuits it was time to hit the road and hope it acts up.

As luck would have it it didn’t take long to occur, but it did it on one of the worst hills in the area to have a car that wasn’t running right. This hill is about a half a mile long and about four hundred feet high with a blind curve in the middle of it, and there was a few moments this really seemed like it might be more than just a cliché as a suicide mission . Here is a screen shot of the camshaft and crankshaft signals while the problem was occurring.

The advantage of having both of those signals at the same time is that they share their powers and grounds which are both provided by the PCM. With the crankshaft sensor signal operating normally, and the five volt reference from the PCM to the camshaft sensor visible, the problem had to be in between the scope connections and the camshaft sensor. Here is a capture taken while the signals were both operating normally for a comparison.

 


Armed with this perspective closer examination of the harness and the connector was in order. The camshaft sensor connector isn’t very easy to reach in the car even though its right on the back of the head. (drivers side of the car).  One of the tricks is to grab the harness with a hook tool and start pushing and pulling on it to try and get the signal to drop out. That wasn’t successful, but when I put the tool right on the connector for the camshaft sensor I could push downward and the signal went open, and pull the connector back up towards the sensor and it would start working again.

Here is an important capture that reveals the circuit fault. Can you tell what part of the circuit is failing?

 
 



Well that’s great, the car has a new sensor and pigtail that were replaced just four months ago and there is clearly something wrong with one of them. So now it was time to shut the engine down, unplug the connector and pull it up where I could see it and this is what I noticed.






If you didn't see it in the first picture, how about this one?

 

 Here is another view.


Looking from the connection side you can see that the middle pin is pushed part way out of the connector. Grabbing the wire with a pair of needle nose pliers I could push the pin all the way into place, and then pull it right back out. Great, the new pigtail has a damaged pin, or pin retainer.

 

Taking the connector apart I could see the plastic retainer was damaged, and looking at the pin closely the terminal space was way too small for the camshaft sensor pin to fit inside. The problem was that the pin was originally flawed, and instead of making a good connection to the sensor, it pushed out of position and for the last few months and a couple thousand miles was simply just
touching the middle pin of the camshaft sensor. With the problem confirmed the easiest thing to do was to repair and then secure the pin in place inside the connector.

The vehicle was put back together and road tested again with no more troubles found. We called the customer to let him know what we found and how we fixed it.  When the customer came to pick up his car he wanted to know how much he owed, and well the answer to that was nothing of course, this is how we provide a warranty for our customers. From our point of view this shouldn’t have happened so it’s up to us to make it right if and when anything like this ever does occur. All told some two hours of labor time are gone over a pin that probably cost a penny for some machine to make a hundred of them. We take it on the chin for our customers and in the end all that’s really important is that we stood behind the work that we did and the materials that we sold. Hopefully our customers recognize that it’s how we handle the problems that are as much the measure of our shop as are our successes the first time around. Even so, it’s an easy choice to do the right thing, but that doesn’t make it a very fun thing to do.