Glow Plugs Location - OM642
 

As I wrote in previous post, I am having an issue with glow plugs on my 2008 E320 Mercedes Benz Bluetec.
Getting a warning about glow plug/glow plug controller on my dash board, I decide to replace the controller and at the same time check the conditions of the glow plugs. Following the glow plug number 1-6 on the female connector from the controller,I found the number 5 as a bad GP.
Now I don't know how are the GP sequence numbers in the engine. How are they numerically located in the engine cylinder head looking the engine from the front of the car?
Also I removed one GP to check the part number in order to buy the correct plug and found all these numbers engraved on it:

CZ 302 7V K72 MK
A 001 159 57 01
NGK

It is a 8 mm Thread.


The new controller is a Beru with Made in Germany engraved on it but the cardboard box says Made in Portugal. After installed and take the car for a drive the glow plug warning went away But I still wanting to replace the bad GP.
Please let me know how to locate the #5 GP.
Thanks

It goes like this

3 6
2 5
1 4
(front)

Thanks Jay

In this car, is it supposed to get a "engine light" when one glow plug goes bad?

Yes my ML320 had the glow symbol and a CEL on one plug failing.

It is important to get this fixed quickly on this engine, they use the glow plugs for far more than starting.

My situation is this: I had the GP warning (symbol) on my dashboard (at the clock) and also the engine light on.
MB mechanic said that the engine light was because the Glow Plug Module was bad and also the DPF was clogged.
I replaced the GP Module and the GP symbol went away but the code was still there. Also a day after replacing the module the engine light also went away and now the car is running like it was before all these issues with DPF, GP module. No more engine light at all.
Today I stopped at Autozone and even with no engine light they still finding codes.
Code P0402 - Exhaust Gas Recirculation Flow Excessive Detected.
Code 0472- Exhaust Pressure sensor low impute
Code P0670 -Glow Plug module Control Circuit.
I had all these codes before doing any work on my car and the car was extremely slow and no power when accelerating.
Should these codes be reset in order to have an accurate reading?
Or should drive more miles to refresh the system?
Car is driving great now but why these codes, specially the GP Module still coming up again?