eddieo45

I thought the CEL only reset itself after a number of starts, I thought 20 or so? Mine has been on/off/on/off over the last week or so (still haven't read code). My wife's E350 had CEL on, code indicated thermostat, and CEL went off even as car continues to run cold.

Rudeney

It depends on the code. Some things, like a loose fuel cap, will go away immediately when solved. More serious error do require several (3, I think) start-stop cycles, and then the MIL only goes out if the condition is no longer present (though the DTC itself will remain stored).

eddieo45

well, it came on again and now that my $20 Amazon.com code reader has arrived I can see that it's a P0016 code it's throwing, crank/camshaft position sensor. That hardly seems like something that's intermittently correcting itself, no?

Yidney

I think most any sensor can throw an intermittent code, if for no other reason than the sensor may be working intermittently.

Rudeney

Eddie, I have some bad news. P0016 = DTC 1201 (P0017 - DTC 1200). These are the tell-tale symptoms of "balance shaft" failure:

http://benzbits.com/BalanceShaftTSB.pdf

Specifically, the timing gear on the balance shaft is stretching and it's allowing the timing chain to run "behind" where it should be. The variable-valve timing system can compensate for up to 20-degrees of difference, but as it detects that the timing chain is not in the right position, it throws an error. If it throws enough errors, it illuminated the MIL. Right now, it's intermittent because the gear teeth are just slightly worn. As the gear continues to deteriorate, the error will become more numerous and the MIL will remain illuminated continuously. If left unrepaired, the gear will completely fail, and many bad things can happen to the timing case, oil pump, oil pan, vales, pistons and cylinders.

My advice - get to your dealer right away and see if they will help you work with MBZ for a goodwill claim (assuming you aren't under an extended warranty).

Yidney

So what code would he have if just the CPS was actually failing?

eddieo45

Rodney,
How many separate repairs are related to that issue? Back in 3/2010, I felt I was being tapped from behind while decelerating/downshifting. That repair (under warranty) replaced clips and springs as well as complete B1 and K1 assemblies. Then last April it went into limp mode and the $1500 repair bill reads "fault in turbine speed sensor," "DTC 0718 stored in ETC," and "replace EHS Conductor Plate." What's "4460 CPMA"? That line item was $871.57

Yidney

Those all sound like transmission repairs, not engine repairs.

eddieo45

lol, shows how little i actually know about our cars! I thought the balance shaft issue was a transmission issue, and I thought it was behind me now. I should probably sell the car.....there's a 2009 CLK550 near me I like.....under 17000 miles but out of warranty.

Rudeney

Yep, those are all transmission repairs. The balance shaft is an internal engine part. The crank shaft drives the cam shaft(s) via a metal timing chain. The V8 engines have a small sprocket bolted onto the front end of the crankshaft that directly drives the chain. V6 engines are inherently "unbalanced" so they add an extra "balance shaft" running parallel to the drive shaft in order to help counteract vibrations. A gear forged as part of the balance shaft is used to drive the timing chain on the V6. The supplier that forged these parts (gear on the V8, entire balance shaft on the V6) screwed up and made some of them too soft. The timing chain wears down the gear teeth (see the pics in the TSB I posted) and things start getting out of time.

My advice if you are going to trade, do it NOW! This problem will only get worse and the MIL will eventually be illuminated constantly. Even if you reset the code, a code will be thrown and the MIL will illuminate immediately upon starting the car. It's a $4K+++ repair out of warranty (the entire engine has to be pulled).

eddieo45

Well, the last couple of days have been crazy as I look for a new car and take care of a few things on mine before selling. My wife and a friend both think I'm crazy to be putting such faith in Rodney's assessment and acting so fast. I was asked "what if it's just a bad sensor?"

Yidney

That was the question I asked just a few posts up. Presumably cars in the balace shaft VIN range can also exhibit a CPS code for other reasons - such as a bad CPS. And a bad CPS is a common problem on these cars. Maybe Rodney has some other reason why it cannot possibly be that. I always thought the balance shaft issue threw 2 codes, and you only reported one.

eddieo45

The light is on for the 3rd time, and the $20 code reader does say 2 codes, but both seem to be P0016. I'm having it sold at auction tomw; hopefully end up with a 2009 CLK550.

Rudeney

DTCs 1200/1208 (a.k.a OBDII codes P0017/P0016) are:

1200 Constant adjustment of exhaust camshaft of right cylinder bank in direction 'Retarded' (P0017)
1208 Constant adjustment of intake camshaft of right cylinder bank in direction 'Retarded' (P0016)

Basically, the CPS is a Hall Effect sensor that is triggered every time a magnet on the flywheel passes under it. I believe there are 18 magnets (one every 20 degrees) on the flywheel. It can't sense the actual position - just that it rotates 20 degrees at a time. The ECU determines which cylinder to fire based on the camshaft timing. So, if the camshaft sensors don't quite match one of the 20-degree marks on the CPS, you get an error. The variable timing system can still compensate, but these DTCs let you know "something isn't right".

A bad CPS would not be giving consistently wrong positions - it would either quit working altogether (which would cause the ECU to shut down the engine, assuming it had stopped rotating) or it would be very intermittent, which would either shut down the engine, or cause it to run poorly. When the CPS is returning a consistent signal that is just not in sync with the angle of the crankshafts, the only cause can be that the timing chain is not in the right position. 1201 and 1208 indicate that they are "retarded" or running "behind schedule" of the CPS. This is because the gear driving the timing chain is stretched, which moves the crank ahead of the timing chain, putting the camshafts "behind schedule".

I know this is really hard to explain in text, but that's my best attempt. I can assure you that if you have an engine in the affected range, and you are getting 1200/1208 DTCs, you have a 99.999% chance of it being due to "balance shaft" failure as explained in the TSB.