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My check engine light came on yesterday and car went into limp mode
I scanned the car and came up with codes P2403 and P2402 as well as a bunch of misfire codes with I believe are due to the car being in limp mode but I could be wrong. Any help is appreciated
Hi the two p-codes are to do with the tank pressurization system that checks for gas (petrol) vapor leaks form the fuel tank (least of your problems and is unrelated to limp mode).
By limp mode you mean that the engine not running on all cyl's correct? Something that you need to do is to note down all the error codes then clear them and see what comes back.
The misfire codes are a real worry and is usually coil packs or air mass meter or both.
Coils are a complete unit for left and right bank (ref image). Warning!! even though the individual coils look and feel like they come out do not attempt to remove as the welded link inside will break as they are turned and pulled.
It could also be faulty/dirty spark plugs.
Other members here please advise more on this problem as all but one car I had repaired needed coil packs (the odd one out needed and engine - low compression).
The other stuff:
Being general OBDII codes it's not always clear as to what the system is complaining about - they are not always right (in my experience).
2402 is for the pressurization pump motor open circuit or disconnected and 2403 is for the pump sensor signal high (is this a rotation sensor or the pressure sensor??). I'll need to have a dig through the circuit diagrams.
If it's the pressure sensor it's located up near the filler neck.
For the pump I'll need to have a look on WIS as to where it is.
All that having been said please just dont replace parts yet as both error codes seem to suggest either a bad earth or corrosion/poor connected somewhere.
I'll post the appropriate diagrams later today.
2009 S550 AMG sport pckg. 2014 Ford F-150 Lariat Supercrewcab
Yes a bad MAF or coils can cause the issue. A bad MAF would usually cause a lean condition at higher RPM and show up as richer fuel trims than at idle. Maybe also set a P0171/174 code. A good way to tell if the MAF sensor is bad is to just unplug it and see if the car drive better. Some computers use a preset fuel trim map and try to guess the fuel load, which is not perfect but will usually do better than garbage info from a bad sensor. If unplugging the MAF makes it run better it's most likely that. Also a bad MAF will cause a huge lack of power. I saw a 2000 Ml320 with this issue that couldn't even budge 18mph. unplugged the MAF and it ran better. It also had misfire codes from the MAF. Put in a new and all was good
Last edited by Nickthegreek; 11-27-2015 at 06:52 PM.
Hi sorry for the delay but i am having difficulty finding info on the evaporative emissions system on my version of WIS (Workshop Information System).
Mine is set for Europe and consequently seems to have very little on the US only systems.
I could only find a block diagram that shows that the two control vales in the charcoal canister and tank pressure sensor are controlled directly by the engine computer.
I'll need to see if i can switch the service region to USA and try again.
as user greglig already stated this indicates that one of the coilpacks seems to give up.
I also had misfire on serveral cylinders and had to replace the coil pack.
Typically for the V12 @ around 100.000km.
My advice is to clear the DTCs and start engine again. If misfire will be set again, it seems you will have to replace the coil pack.
But keep in mind that if cylinders fail unburned fuel will be pushed into your catalythic converter which can be causing severe damage if engine runs longer.
If Coilpack is to be replaced be aware that during installation they tend to break. I would Mercedes handle repairing. They will also change the spark plugs (12x) if they change the pack
Costs were here in Germany at around 1300€ per coil pack incl. installation
I did the coil packs on my s600 recently...expensive...but it was covered under warranty. If you end up doing it, you might as well do your spark plugs too. That was an additional 800.00 I think.
Mercedes will also change the spark plugs if doing the coil pack swap.
Every Coil Pack (left or right bank) does have 12 spark plugs. V12 does have 24 in total.
As stated above, replacement costs for new coil pack, 12 spark plugs (BOSCH) and installation was around 1300€ at Mercedes Niederlassung (Dealership in German). I originally wanted to do the swap by my self
but mercedes disadvised me due to the possibility of cracking the coild pack (verrrryy fragile!!) during installation
They won't do it automatically, they will ask you and then tell you it will be around 800.00 to do it as it's separate from doing the coil packs. You would think it would make sense to just do it while they are there but the labor is charged separate.
The packs at the dealer are 1400.00 per side.
You are looking at around 4k-4500.00 to do both sides and the plugs.
Just a bit of general knowledge info here and something people don't realize and often overlook.
Spark plugs (and leads in non coil on plug systems) are very important and can be the cause of a coil failure.
When the coil is correctly "loaded" with an appropriate spark gap the secondary winding voltage does not climb excessively high and stays withing design limits.
By "spark gap" I mean effective distance between the high tension output to ground and not just the actual plug gap at the end.
For example lets say the spark plug gap is 1.5mm and needs 5000 volts (5kv) to jump the gap at normal atmospheric pressure, cylinder pressures are much higher under normal operation and it could become 10mm requiring 30kv to jump the gap.
When everything is working as it should these values are not exceeded an all is ok. When you have a bad plug or lead the effective gap is wider and a higher voltage is needed to jump the gap eg: 20mm or more. Seconday high tension side of the coil could climb to 50-60-70+ kv. What happens next is the high secondary voltage punches holes in the insulation and you get internal arching between adjacent windings damaging the coil. Secondary coil windings are thinner than your hair and still use lacquer as insulation.
This is another reason that modern coil on plug coils should never be run with nothing in the end. The damage happens little by little and gets worse over time.
The old GT40 coils (large round oil filled coils) were indestructible you could do anything you wanted.
Please note values given above are just a general example and by no means are to be taken as actual values seen on a car.
Back to the MB v12:
I think MB-USA should insist that you do plugs when the coil packs are replaced to eliminate the possibility of killing a new coil pack with bad plugs.
As Florian-S600 stated MB Germany will do both at the same time but different countries have different polices.
I think another reason the coils fail on the V12 is heat and potentially being driven too hard by design (even though they claim longer life and less load). This is a very complex system involving a separate control module on top of the engine computer.
11-27-2015, 02:49 PM
Other members here please advise more on this problem as all but one car I had repaired needed coil packs (the odd one out needed and engine - low compression).
