e300d crankcase position sensor
 

I'm posting for my Dad who has a 96 E300D

At the end of last winter the car started stalling intermittently and got worse. The CCPS was replaced and fixed the problem.

At the end of the summer the same thing started happening. The CCPS was found to be bad and replaced again.

For a few weeks the car ran and started acting the same way. The CCPS sensor was bad again and with a replacement the car is running again.

Is there anything wiring wise that would cause this sensor to short out.? There are no signs of physical marring when they are taken out. If there is a potential shorting of the harness does anyone know where the sensor is located and where it taps into the computer and ground (I assume it's a send and ground wiring harness) so new wires can be ran between the two points?

Thanks!

Is there evidence of it shorting?

In our diesels, the SOV (leaking, failing or bad K4 relay interrupting power supply) exhibits the same type of symptoms as the classic CPS failure in a gasser.

Though the k40 is a common cause of intermittent stalling, it is not the problem in this case. Each time the CCPS was tested, was bad, and a new one was the only thing that made the car run. Also, the k40 relay was re soldered to make sure that wasn't the problem.

Just an idea, but you state that the K40 relay was re soldered. As with any solid state circuit board, there is always the possibility of an unintentional "tracing" the point your are soldering to another point on the board. I have had that happen when making modifications to computer circuit boards. With the naked eye, it looks like the solder joint is clean, but in actuality, the integrity of the connection was compromised by a trace line of either solder or flux to another point on the board. Since you have replaced the CPS 3 times already, I would go with getting a new K-40 relay and see what happens. Good luck

The k40 was soldered by an electrical engineer with a magnifying glass. Also, the ccps was replaced once before the soldering and twice after, which makes it seem like there is no difference. Lastly, the car was running, just stalling a number of times, before and after the solder job, so the soldering didn't make a difference in performance in the vehicle.

If there is some circuitry in a K40 that could be crossing that would blow the CCPS then that would explain why the CCPS's are internally blowing out and not sending a signal when tested. Does anyone know if they are linked and how?

What does the CPS do on our diesels. Provide a reference for RPM and maybe cruise? I don't think that input is as critical as it would be on a gasser.

Most folks who have repaired a K40 end up getting a new one not long after in my expirience.

Probably provides RPM reference for idle speed management, rev limiter and lets ECU know the car is running for the "auto start" function. I'd like to know more about it myself...

Is the car stalling only at idle? Does it seem to have trouble maintianing a steady idle when it stalls or does it stall at higher RPM's and speeds as well?

The sensor is on the left side of the engine at the back in the rounded part of the block that joins the transmission. The wires pass out of the sensor and around the starter and are incorporated into the starter wiring harness to go wherever that goes. Maybe the sensor wires are getting too close to something related to the starter and they're getting an EMP from the starter or it's wiring which finally kills the sonsor... shrug...

This came out of my shop manual, and the manual contains about 10 different sections as to how to check it.

The task of the crankshaft position sensor is to detect the position and speed of the crankshaft through a non-contact measurements using the segments provided on the drive plate, or the flywheel, and to supply the corresponding signals to the IFI (ERE) control module(N3/7) or the DFI(EVE) control module.


The crankshaft position and engine speed are detected with no contact required. With the engine running, the leading and trailing edges of the flywheel segments generate an alternating voltage through induction in the crankshaft position sensor. The higher the engine speed, the higher the voltage.

From a respected tech: Provides ref data used by AC, some emissions components and signal for RPM gage.

I fail to see how the CPS can stall the car. I'd unplug it as see if your stalling issues cease; if it does look to the K40 relay, SOV and a new mechanic.

To clarify; The car had an intermittent stalling problem that then became a no start problem. Before each time the CPS was replaced the car would not start at all. After a new one went in it would start and after a while start having intermittent stalling and eventually a no start issue again. The SOV was replaced already during the one of the times the car didn't start at all.

The next time it is in a no start mode you need to pop the hood and listen for the click of the SOV when the key is turned to pos 2.

No click = no start = bad K40 relay.

One of the test procedures regarding the crankshaft sensor indicates that a malfunction could be due to "Contaminated position segments on the flywheel disk" (metal swarf). Metal swarf are metal shavings or metal dust that will adhere to the flywheel "disk position segments". My thinking is that since the sensor itself generates its own voltage via the "position segments", if those segments are somehow contaminated with metal shavings, it could possibly overload the sensor itself causing it to burn out prematurely.

Would cleaning the flywheel solve the problem?

If "metal swarf" is causing the problem, then cleaning the flywheel segment areas should cure it. If I were in your shoes, I would swap out the k-40 relay. It is not that expensive a part, and that would eliminate all suspicion regarding its integrity. If that fails to remedy the problem, then you could follow through with the possible flywheel issue if any.