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Hi,
my 2002 C240 would crank, but would not start.
I then bought this USB OBDII scantool and have it plugged to a notebook and it gives no trouble codes. This morning, a service person came to my neighbor and my neighbor have him come over to give my C240 a quick check. He brought in a handheld scantool also with an OBDII interface and yet he too can't find any trouble codes.
Neighbor says he once saw a similar C240 scanned using two plugs: an OBDII and also a huge round plug that only Benz uses. He suggests, perhaps that other round plug was needed to give a thorough scan. I unscrew the plastic cover underneath the steering wheel but found no such plug.
Is it true that the C240 have 2 different plugs? If it does, where can this be found? If it doesn't, is there any other approach when an OBDII scan gives zero error readings?
Thank you in advance.

SL-ML-C

my vote is a bad battery in your key, a bad Crank Position Sensor, or a bad Cam Position sensor.

mleskovar

The key does not even need a battery to work the ignition. I don't know if a m112 engine has a cam position sensor....if it does, it is a very low failure item because I haven't read of one failing. The CPS is a high failure item and it doesn't show up on OBDII and matches your symptoms.

SL-ML-C

my M113 has got a cam pos. sensor in it, and it went out before my CrankPS did.

the key's transponder has a capacitor in it, and I have had it go bad causing the ECM not to let the car start.

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Many thanks for the response
Key battery was changed not too long ago.
So that leaves the Crank Position and the Cam Position sensors.
Would a bad Cam Position not show on an OBDII scan too?
If it doesnt, then we've got it narrowed down to the Crank Position sensor =)

EDIT:
Sorry I should've mentioned this earlier.
I'm not sure if this have anything to do with the car not starting, but a couple of months before it died out, when shifting transmissions (automatic) the car would jump quite a bit.
and sometimes on the Instrument Cluster, the Transmission Position Indicator (P,R,N,D) and W/S program selection would not show. When it doesnt, the car would not start.
Unplugging the key and trying it again a few times would sometimes make them appear again, then car would start. But now it never shows anymore.
Hope it all relates to the CPS

TMAllison

The key battery power the door functions.

The CPS normally doesnt create a code. Is like someone turned the key off while driving. Usually will restart after it has cooled down 60 minutes though, until it fails completely.

SL-ML-C

the key battery powers the keyless entry, yes - the transponder chip and capacitor that charge through the ignition (controls the immobilizer) is separate, and can fail from time to time.

pull your CPS, and run an ohmmeter through it while heating it with a heat gun and watch for abnormalities when hot.

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So CPS problems only arises when it gets hot? problem is, in my case, its actually quite the opposite. Before it went completely dead, every morning it was difficult to start. Would have to keep trying until the "P" transmission sign appears.
But once it started, it would be much easier to start again even after quite a long drive and have it parked just for 5-10 minutes.
Would this also mean its not the CPS failure?

mleskovar

Could be this.....

https://mbworld.org/forums/c-class-w...-replaced.html