dirk1984

Hi there guys. 1st time posting something but have been lurking for many years! HA HA!

I just would like to get some input from the community on a issue Im having with a W218 Cls63. M157 engine. 2011 model if I'm not mistaken.

Issue I'm having is the car went to different workshop where they wanted to do a tune and found on a dyno run the car does not make power and it has a laggy gearshift.
When they switch the car off and on the gearshift clears up to fast solid shifts and vehicle pulls much harder. One dyno run showed 200kw and 400nm. When they switched vehicle
off and on and dyno'd it again suddenly went to 350kw and 700nm,but after a while or repeated tests the vehicle would lose power again.

They came to me and I did a short test and found everything on vehicle good except in M.E I have a code of P033284:
Knock sensor 1 (CYLINDER BANK 2) has a short circuit to ground. A signal is below the permissible limit value.

While I was still working at Mercedes years ago the M157 had just come out before I left to start my own shop and I have a fair bit of experience on the M156.
I try and specialize in Merc's at my shop and we have good understanding of the vehicles. Anyway's,I saw the code would move from stored to current & stored each time the ignition is
cycled. Code will clear and vehicle will pull like a train and then suddenly I would feel a very slow bad gearshift and look at codes and find the mentioned code is current. Switch off and clear and
vehicle would fly again for a bit until does it again.

I went ahead and checked all connections,wires etc.and finally decided to just replace sensors. As you guys will likely know they are located underneath intake manifold. I removed everything,not such a bad job,just lots of strip work,but luckily I've always found to be logical in how they route wires etc. Manifold and cooler off,I removed intercooler and had it tested,all good. I checked the wires around exposed knock sensors and found all good but ordered a replacement set in any-case and replaced them when sensors arrived.

When the replacement was done and codes cleared I took vehicle for a drive and found all good when suddenly I had a poor gearshift and then when I scanned I found the same code to be back.
No other fault codes. Just like before.

Car is in very good condition.
Has 150k km on clock.
We did a oil and filter and air filter change while were at it. Wanted to change plugs although the maintenance record suggests it was done 50k km ago,I did not do a plug change in the end as some of the suppressors are quite stuck on there and Merc in South - Africa does not have stock in country of the part so I was not going to risk damage. There are no misfire codes as stated anyway.Everything is good,except low power and this code. Also,it does not switch on MIL light.If you did not scan it you would never know,only when you wanted AMG power on a pull away or when trying to overtake you would not say there is something wrong with car.

I would thus really appreciate any ideas or feedback of what my fault could be. Where can I go look?

Thank you and best regards: Dirk van Zyl. Cape-Town. South-Africa.

C32owner

Hey Dirk. I'm very keen to hear what the problem is when you discover it. Also keen to hear which tuner the owner goes with and what results he gets before and after dyno runs if you able to share.

Only thing I can think of right now and suggest further if its truly a knock the sensor is picking up, maybe try adding some octane booster to the tank, or ethanol.. Something to raise the octane and see if you can do a few WOT pulls and see if the code pops back up.. On a stock motor with increased octane it really shouldn't be knocking. Maybe that sensor is a little to sensitive, idk ?

C32owner

Edit: I know you didn't want to change plugs, maybe you can just replace the problematic bank plugs to?

Also found some posts now of the intercooler system affecting power massively. I think a good check up of the intercooler system, checking it is bled properly and pump operating correctly. Check your IAT temps efc while on a pull... Could very well be a heat issue with Intake temps, hence a data log will be great to do.

dirk1984

Good day. Found problem yesterday evening and car was re run this morning. Did not have time to post again. Went through all the wires again all the way to the control unit. The connector on ECU plug the wire was not making contact as it looks like it burnt. I suspect the knock sensor when it friend caused a short. Because it was on the physical pin it shows no break in wire any where because there is no break. The problem was the physical connection in ECU plug to ECU.

I am not sure what tune is going with,I would like to have gone down to a colder plug but not risking it with the suppressors. When there is stock I will do that Colder plug will enable more boost.

Car was run this morning and now makes 393 kw and 777nm stock. I will try and post a pic now. The man said he will send me another pic after tune.

Thanx for the input. Appreciate it.

dirk1984

C32owner

Awesome, well done on tracing the fault. That's a bugger! I'm sure client is well pleased. That stock power is very strong. I know a couple of Cape Town dynos power figures are to the crank and not at the wheels. Is these numbers at the crank I presume?

Musa's M278

Hello Sir, I have got the same exact problem. I don't have a check engine light yet I have lost so much power. It feels as if somethings holding my vehicle back. I have got a cls550 with the M278 Engine. I don't hear the turbos that well either when I step on the accelerator. This morning I ran a test and I got 2 codes one was P032784 which states that "Knock sensor 1 (Cylinder bank 1) has a short circuit to ground. There is a signal below the permissible limit value" the second code was P033284 which also stated, "Knock sensor 1 (Cylinder bank 2) has a short circuit to the ground. There is a signal below the permissible limit value". I don't know where to begin my diagnostics at this point honestly. Do you suggest anything? I understand that your engine is different than mines but our issue with the vehicle sounds similar. I would appreciate any help. Thank you in advance!!

dirk1984

it was a broken wire in the loon nit far from the sensors. Have to remove manifold etc.

Musa's M278

Thank you for the reply, do you think mines would possible a bad wire as well? but why that effect my turbos? because they don't even sound the way they used to sound.

dirk1984

The sensors determine timing etc.so if no signal boost gets limited.

Musa's M278

Thank you so much for your help, that would make sense for these sensors to limit the boost. Any suggestion as to where I should start fixing this issue? should I just replace the sensors or try to dig in deeper?

gNasty

DId you ever get this fixed? If so, can you explain the process please.