Hi all!

I am a first-time Mercedes owner, and I finally decided to pick one up from a local couple, 134K miles on a 2004 E320. They were up-front about a problem with occasionally non-starting, and I noticed the P0341 code on the ECU before purchase, so I was aware of that.

- NOT cranking at all (25-35% of the time)
- Cranks normally and starts (65-75%)

Thinking this would be a simple sensor replacement, that is the first thing I did - replacing the camshaft position sensor on b1 (passenger side) front of the engine. However, the original symptoms remain, plus now it sometimes cranks without starting at all (as opposed to simply not cranking.) As far as I know, these engines just have the one cam sensor, and b1 on the code should be the passenger side anyway, right?

So, especially since it looked fine when I pulled it out, I'm thinking about putting the original sensor back in, but I'm kind of at a loss - the wiring looks good to me, it's definitely getting power at the position sensor terminal - can anything else commonly throw the P0341 code? Does the cam itself on these engines require any other adjustment?

Second question, do these engines normally have a bit of what sounds like knocking under load? It doesn't make any noise at idle, and the engine seems fine otherwise, just when running up in any gear it makes what sounds like a real faint knock. I haven't seen any shavings in the oil or any other indication, so I'm hoping these engines are just maybe a bit noisy...?

Thanks in advance for all your help!
-Jim

 

Quick update; I found and ordered a Chilton's for the sake of wiring diagrams, so I can begin some more thorough checks of circuitry. I'm surprised how hard it was to find a manual for the 2004 E-series...

I plan to:
- Check continuity for all three sensor wires (ground, 12v, signal) as even good-looking wires can have issues.
- Manually turn engine, key on not started, whilst checking signal wire for varying voltage (hoping the Chilton's will have correct reading range)
- Observe crankshaft position sensor for signs of oil leakage or wear (I've heard crankshaft sensor can sometimes throw p0341)
For the engine sounds:
- Have assistant gently throttle the engine whilst I listen with an automotive stethoscope on the block
- If I don't hear rodknock on the block, I'll chase the sound thru the heads, intake, whatever.
- If I do hear rodknock, I'll be forced to clean out the garage to make room for an overhaul

Wish me luck...
-Jim

 

You can also get a knock off copy of the EPC/WIS on eBay. The WIS is the dealer repair manual and I think the wiring diagrams are also in there somewhere. Not easy to use but it's about $10 or so on eBay. On the sensor, was it an MB sensor or aftermarket? Aftermarket sometimes aren't any good, I would use MB only.

 

Agree with the MB sensors, both cam and crank position, because you have a problem that is evading a straightforward solution. Sensors can look perfect visually and still be faulty. The sensors won’t cause the no crank, though.
Have you scanned for any other DTCs? It seems like the no crank would set at least one unless there is no start signal coming from the ignition switch. That could be the root cause but it’s a rather difficult and pricey replacement to “just try.” Good luck with the wiring diagrams, etc.
The knocking noise is a concern. The E320 engine (M112) is a forever engine when properly maintained. Since it appears only under load, a combination of a bad knock sensor and low octane fuel could be the cause. It’s anyone’s guess without knowing the history.

 

I put the factory cam sensor back in, and the crank/no-start issue went away. So clearly inferior parts, there. It's still throwing P0341 codes though, so I need to source a genuine part. The dealer wants $200, but I'm actually going to the salvage yard on Saturday, so I'll see if I can get lucky and match up two or three cam sensors from the yard cars (based on the stamped Mercedes part # on back of the sensor.) If not, I'll pony up the $200 I guess.

I also replaced the starter relay, and as of today I'm 9 for 9 successful starts in a row. If I get to 20 for 20, I'll feel comfortable that the relay was the issue. If not, I'll attach a test light to the solenoid's +12v and watch for the condition (the aborted 1/10th of a second crank / no start) when it happens, to see if I'm getting +12 there.

The engine knock didn't sound like rods when I checked over things with a stethoscope. I couldn't pick up any noises from either head nor from the block itself. Where's the knock sensor on this car? Should it throw a code if it's failing? The sound only appears under load, it seems.

On a side note, I replaced the engine mounts because of excessive vibration in the cabin when at a stop, and I simply cannot believe the difference. With genuine Mercedes mounts, it's a cloud. I have to keep checking the RPM gauge to believe the engine is actually running at all! Now I know how this car was meant to feel. The passenger side mount was a piece of cake using the alternator-removal approach, driver's side is a PITA though.

On another topic, does anyone have recommendations for a scan tool that can handle a myriad of models & higher level functions? I have a Volvo, Mercedes, Hyundai, Mazda, Dodge, and Honda "in the family" to take care of, and it'd be cool to be able to do all the things (TPMS, key fob programming, SRS fault analysis, graphing of the cam pos. sensor, etc.) There are a ton of them on Amazon and I have no idea what's really a good one for a shadetree mechanic like me. If anyone has a recommendation, I'd appreciate it.

Thanks!