1997 E320 camshaft position sensor
 

I'm helping a friend clear a check engine light code for the camshaft position sensor in a 1997 E320. I need to check the sensor and wiring and reset the CEL.

Can somebody please post a wiring diagram to tell me where the wire going to the camshaft position sensor ends up. I'd like to check continuity to be sure the wire is well insulated and not broken in the harness.

Also, is there a way to check the functioning of the position sensor without having an oscilloscope. I assume it works by sensing a magnet on the camshaft gear passing by. Not sure how to easily measure that event.

I'll also check that it has the 0.4 - 0.6 mm gap between the end and the camshaft (gear?).

Thanks,

Paul

Can anybody confirm ...
 

that there is a need to verify this clearance?

CPS signal is .8-1.5 a/c V. at crank/idle rpm.

Arthur ...
 

looks like you might be out there this evening. Saw something in another of your posts about verifying the gap on a CPS. Is it an issue with this model of car (1997 E329)? If so, do shims come with replacement unit and how is it done as sensor looks like something that inserts into the cam gear cover. Thanks.

If the sensor signal meets Voltage specs, then the spacing is OK.
If you change the sensor, then you want to check the spacing for clearence [.5mm/ .020"]. There are spacer/shim washers that go between the sensor and the mounting hole to make that adjustment.

Don't confuse the cam sesnor and the cam advance magnet...they are completely different, and often confused. The advance is on te front and the cam sesnor is on the side.....

Thanks, Arthur ...
 

my car is throwing code P0341. Went to run some arrands this PM and on the way out it missed badly which has never happened. On the way back, it stumbled at startup and when i got it out on the road, I accelerated briskly to see what would happen. Car ran very roughly and turned on CEL. I pulled codes when I got home (Car ran roughly all the way but it was a short distance). There was also a Cylinder 2 Misfire code in the memory. Think I should try a new camshaft position sensor it connections are clean and tight?

I would change the 3 plug connectors a under the coils..common , maint. item and the most common cause of mis-fire on 104 DIS ignitioned engines

Thanks again, Arthur ...
 

my under-the-coil connectors are only about 20,000 miles old but I will replace them.

Thanks Arthur,

I'll check the AC volts for sensor function.

Any help on checking wiring? I'd like to verify continuity. Where do they lead, what pins on computer??

ALso, clearing the code using a OBDII meter rest the CEL but left the code in the computer. The CEL returned, and I'm not sure if this means there is a problem with the camshaft position sensor or circuit, or if I need to clear the computer entirely. This time I'm going to use the battery method, to verify I can get the code to disappear. Then if it comes back I will know it isn't a one-time fluke!

thoughts?

Paul

If they are that new , I would hold up on changing them.
Does the car have Plats??????


For original poster:

The sensor should ohm out at 900-1600 ohms. I don't have the pin #s for that chassis.

Hello again, Arthur ...
 

no my car has OEM plugs, Bosch F8DC4. After pulling the first set of codes, I cleared them and as I was putting car in the garage, CEL light came on again.
Just pulled that code this morning and again see CYLINDER 2 MISFIRE. Car started fine and ran smoothly but goes to rough idle about 15 seconds after startup. Is cylinder 2 one of the ones which uses the short connected under the coil? Thanks.

Swap that coil with one of the others and see if the code follows the coil.

Arthur, need next thoughts ...
 

after looking at my records, I discovered that the plugs and coil-to-plug connectors had about 40k miles on them. So I got three new connectors from dealer and replaced them and all plugs today. Car seemed to run very smoothly upon startup so I went for a drive. After a couple of miles and while accelerating up a grade, CEL came on and car went to rough idle at the next stop. Drove home and again read out code P0302 (CYLINDER 2 MISFIRE). This was third time it has come up after clearing it the previous two times. The code concerning the camshaft position sensor has not returned after the initial appearance. Is it possible that the coil serving Cylinders 1 &2 is defective? Can anybody explain how one coil is made to serve two cylinders?

Like I told you on the last post...swap the coil with one of the others and see if the code follows the coil swap....... Simple.

You have a Waste Spark Ignition using one coil to fire two plugs that are wired in Series..... a Series Circuit.

Use the Archieves ,,,there are pages upon pages on this .

Back to the 1997 E320 camshaft position sensor issue!

I went to check for the 1 kilo-Ohm impedance, and 1 V AC in idle of the camshaft position sensor. I found that the sensor had three terminals, not two as I expected
The resistance was very high across each terminal pair - like 100 KOhm or more (open circuit)

and when the car was started, I could detect no AC voltage at all between any pair of terminals.

Arthur?? I don't understand how the sensor works, and I'd like to see if it functions.

I tested the CamPS on our family car (2 terminal) and it measured 2 kOhm just like Arthur said.

Is anybody familiar with tests for the three terminal sensors - or does this one sound like it's dead?

Also, could the magnet have come off the camshaft gear sprocket?

TIA,

Paul

This may help ....
 

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

<I found that the sensor had three terminals, not two as I expected
>

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.

<<Can anybody explain how one coil is made to serve two cylinders? >>

Waste Spark.

I'll try to send diagram of camshaft position sensor ..
 

which is from Alldata. Bear with me.

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

A related question ...
 

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

P0302 Code Resolved ..
 

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

If I was going to check this sensor ....
 

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.

<<I'll also see if there is an AC voltage on the switch when the car is running. >>



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 .......