VanHiest

Hello!
First of all I want to say that I've done an extensive research and tried quite a few things prior to writing this extensive post.

The story
2003 CLK320 coupe. Below -20C outside. Drove it in the morning with no issues. Started and went from my job to a store with no issues. After shopping decided to reset the ECM: code reader failed to find throttle valve end positions. After this the car is starting and immediately quitting.

What I know
I use iCarsoft MBII, software is up to date. I used it to reset the ECM multiple times prior to this as I was troubleshooting the Limp Home Mode due to a tranny fault. Reset was successful each time. Transmission was sorted the day prior.
MBII shows no DTCs, shows that the MAF, throttle valve angle, temperature and all the other sensors are operational. But also shows that throttle end positions are not recorded.
Fuel tank is 80% full with 89 gas (now boosted, see below). Fuel pressure on the rail is between 50 and 60 psi prior, during and after start.
Battery was good initially. Now I only try to start it with installed booster cables from another running vehicle, system reading 13.5V.
Starts are normal, fairly quick with no misfires. Quitting is also quick, always happening within 1-2 seconds, but not as abrupt as when I turn the key to OFF. No CEL.

What I tried
Fuel pressure measured at the rail. Reading is normal.
Dumped a bottle of fuel booster in the tank.
Tried starting with MAF disconnected.
Removed, cleaned and inspected the throttle valve. Operates under voltage.
Replaced camshaft position sensor. CPS was replaced recently too.
Tried resetting throttle using several procedures I found online. No throttle valve movement noted.
Tried starting with throttle valve pried open manually to a various degree: usually quits even faster, with a clap.
Tried starting with EVAP ports taped up - no change.
Supplied 12v to the throttle valve motor on the ECM end of the harness: throttle valve opens normally.
Removed and examined the ECM - no damage inside or outside. Reinstalled and tried starting while the unit is warm - no change.

Guesses / Next steps
I figure that ECM failing to find the throttle valve end positions is either a symptom or a cause of the problem. Yet I'd think there would be codes thrown at me, CEL and some kind of safe operation mode. Unless it is the ECM that failed and it's not aware of it.
Couple other options I can think of is badly contaminated fuel or an aftermarket alarm that I'm not aware of.
I am now looking for a person here in Calgary with a Mercedes of the same era, to hook up my code reader and compare the readings.

Meanwhile, any input would be appreciated!

Rudeney

So it actually fires and runs briefly and there are no codes? When it runs, is it smooth or laboring? Also, do you have a spare key (if not, get one) and does it react the same with both keys?

VanHiest

Yes to you first question.
It runs smooth.
Unfortunately, I don't have a second key.

Rudeney

What is the actual code you are getting for the throttle valve end position error?

VanHiest

No code. It's one of the readouts. Under the ECU I can find "Throttle valve end positions learned" - "NO".

Rudeney

Oh, that just means that it needs a throttle sync. I don't know if the iCarsoft MBII has a function for that or not. Try this

1. Make sure everything in the car is turned off and closed.
2. Turn the key to position 2 so all the dash lights are illuminated.
3. Press the accelerator fully to the floor, depressing the "kick-down" button.
4. Hold he pedal for 5 seconds and continue to hold it down.
5. Turn the ignition switch back one click to position 1.
6. Release the accelerator pedal, but leave the key in position 1.
7. Sit quietly and wait for about two minutes - do NOT open or turn anything on.
8. Listen for a "click" or "ping" noise form the dash.
9. Start the engine and drive the car for at least five minutes.

VanHiest

Thanks, I tried this. No noises appear and nothing changes

Rudeney

Have you scanned all systems with iCarsoft, like the EIS, SAMs, etc?

VanHiest

Yes I did

Rudeney

Well, I have nothing else to suggest. I think the MBII has live data recording. You might play around with that to see if it shows anything interesting.