Mike P

My 1993(low mileage, seldom used) 600SL had a "Check Engine" light while idling. My local shop downloaded the code which indicated a "crank sensor". The idle was somewhat erratic, slightly high(800-900rpm) and then the ASR light came on. The fault was cleared but later returned. The shop seems to think that the sensor is "bad" or needs to be cleaned.

Where is the sensor and does this make sense? These cars are starting to scare me, especially since I have an SL65 on order.

Thank you in advance,
Mike

stonechip

You could have two problems:

The “check engine light” is triggered mostly by the emission control system. The usual suspect in this case is a bad oxygen sensor, I had a BMW 750 with this problem and after replacing over $ 7,000 in cover parts, the problem continued. They finally realized that the car comes with two oxygen sensors and they only replaced one. I jettisoned the car after that.

So have them check the oxygen sensors, I believe the SL600 may also come equipped with two.

The second problem is what happened with my current SL500. The ASR light came on, and off and I ignored it for a couple of days. The third day the light stay on and the car would barely move. I finally made it home.

The ASR control module (Computer) ASR motors, and ASR sensor sending units went south, they need to be replaced. The car will only drive at ¾ of the engine speed and the tachometer can become erratic while driving. Total cost for part and labor, out of guarantee, $ 4,620; I am not sure with the V12. If the ASR is coming on I have a bad feeling that the hardware, based on the year of the car, may need to be replaced.

Mike P

Stonechip:

Thank you for your reply and sharing of your personal experiance but I'm still confused. The downloaded fault code indicated a faulty crank sensor. Do you still think it's an oxygen sensor related problem? Is it possible that the ASR computer is being fooled by a faulty crank sensor, especially when it comes on while parked?

Mike P

blueSL

Normally the crank position sensor picks up information from the edge of the flywheel at the back of the engine, into which the starter motor engages and it's purpose is to synchronise the mechanical and electrical operation of the engine (ignition, injection and so on).

It should not be mega-bucks to replace.

BarryFish

If it's after warm-up, the crank sensor is known to cause intermittent problems. Since you said idle, that might indicate a thermally sensitive problem. Idle means low cooling air flow and a hotter sensor.

Have it checked twice. pay once.

Best Regards,

Barry