a diagram I have shows that the camshaft position sensor contains a P-N-P transistor. Output signal for the sensor is at a constant 12 volts until the magnet passes the sensor and the induced voltage acting on the transistor drops the signal voltage to 0 for a brief time. This tells the controller that the number one cylinder is at TDC and the contoller uses this with other signal s from other sensors to make engine management decisions.

Ah.. a transistor! so high impedance is normal.

So is this the circuit??


one terminal (+12)
|
<
> Resistor (100 K ??)
<
|....................................... signal (+12 or 0.6 V)
/
magnet------| transistor
\
third terminal (neutral)

So I need to connect a battery across two terminals and measure a switching voltage on the third.

So if sensor works, I put +12 V across two terminals and measured an AC voltage on the third>

Any idea which pin is which??

Paul

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1983 500 SL (Gone )
1972 350 SL 4.5

>

That would be the later style sensor....the info I posted was for HFM 2 wire sensor, so that would be invalid info for the 3 wire. The 2 wire is a VR [ variable reluctor ] Sensor . The 3 wire requires V input from the ECU and switches that signal on/off.
I do not know when they made that change, as my CD is from '95/104 systems. Prob when they went from HFM to Motronic/OBD2. [ '96]
As OKC 's post shows, this 3 wire is a switching sensor, where the 2 wire is a sine wave sensor [ like an ABS wheel sensor type];
The newer sensor is much better b/c it actually switches the signal, thereby giving you a square wave , On/Off signal. Whereas the 2 wire is a signal generator and you wind up with a variable voltage a/c sine wave...no where as acurate as the square wave format. I would make sure the end of the sensor is clean of debries.

<>

Waste Spark.

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__________________
A Dalton

which is from Alldata. Bear with me.

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You can see the square wave............

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A Dalton

when OBDII posts a cylinder misfire code, what was actually detected? What was measured or sensed by the engine management system?

put new ignition coil in for cylinders 2&5. Car is running good again.

Back to the 1997 E320 camshaft position sensor problem!

This weekend I plan to check the functioning of the sensor and wiring, and check the magnet in the camshaft gear.

1.) I figure I can remove the sensor and check the voltages (+12, ground, and switching either 0 or +12) I plan to use an external magnet.

2.) I plan to rotate the engine using a remote starter switch till I can see the magnet in the camshaft gear (does anybody know what it looks like?) and check that it hasn't fallen out - I'll use a nail to check the pull.

3.) I will reinstall the camshaft position sensor and see that the magnet in the camshaft gear switches it - & rotate the engine to check it go on and off. I'll also see if there is an AC voltage on the switch when the car is running.

4.) The problem may be electromagnetic interference as the CPS wires run near the spark plug wires. I've read that EMI noise can confuse the computer and sometimes can be large if improper plugs or wires are used, or the the routing of the CPS cable is too close to sources of EMI.

5.) I might even use a braid to shield the cable.

Anything I missed? and does anybody know what the camshaft magnet will look like through the camshaft position sensor hole?

thanks,

Paul

__________________
1983 500 SL (Gone )
1972 350 SL 4.5

I would proceed a little differently. Since the spacing between the sensor and the magnet on the cam gear is critical, I'd unplug the connector and insert some very fine wires into each pin position (just individual strands from a scrap piece of stranded wire), then refasten the connector. Don't force it if it won't go back together. Keep strands separated so there are no shorts. Then use your voltmeter and try to detect the signal pulses each time the magnet goes by. I'm not sure, from the diagram, which two pins you'll find the signal on and since it is a narrow pulse, the meter will probably just blip. Looks like I'd connect the ground of the meter to Pin 1 and the positive lead to Pin 2 for starters. (Make sue Pin 3 is carrying +12 volts with respect to Pin 1.) This would at least give you an indication that the sensor was or was not functioning. Good luck.

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You will not see an AC voltage signal on this type of sensor. It is a Hall Effect sensor and it triggers DC On/OFF. That is the advantage of this 3 wire sensor over the Induction , 2 wire sensors [ they are AC V output]

Your sensor has a 12 V feed from the ECU [+ and - to power the IC of the sensor] and the third wire is the triggered on/off signal back to the ECU.
So, you want to see a constant 12v at the + and - pins, and a pulsed, DC signal at the third pin, which is the sensors switched output signal to the ECU. This is a switching sensor, unlike the 2 wire AC voltage generator sensor .......

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A Dalton