I thought I would share a bit of a story that happened to me this weekend, in the hope that it will help some others if the same thing happens to them.
The model it concerns is any 300C with the Mercedes 3 litre V6 diesel. I'm guessing the newer models with the VM diesel will be totally different.
So there we are, on the way to Wakefield from Essex where we live, merrily trotting along the motorway. All of a sudden the dashboard starts to chime repeatedly (as if i've left the headlights on and got out), the engine cuts out completely, and on the dashboard are the engine management light, and the red lightening bolt, with a reverse bracket either side (see attached photo).
We coast to a stop onto the hard shoulder, and i try to restart the car. It turns over and over, but refuses to fire up.
The missus gets on the phone to the RAC, and we're told there's roughly a two hour wait, so this gives me a bit of time to do some Googling before the patrol arrives.
Now then, if you refer to the handbook, it clearly states (even in the diesel supplement) that the lightening bolt light indicates there is a fault with the "Electronic Throttle Control". This is utter nonsense. As it turns out, on the diesel models only, this light refers to a fault with either the Swirl Flap Motor, or the Turbo Actuator. Annoyingly this isnt listed in any of the handbooks that come with the car. Poor show Chrysler!
Whenever you turn the ignition on in the car, you can see the arm of the turbo actuator raise up. So if this is the problem, then its very easy to diagnose. I tried this little test, and sure enough, the turbo actuator arm wasn't popping up when my wife turned the ignition on, so naturally I thought this was the problem. Sadly I was wrong.
What had happened to my car was this....
Over time, the seal around the air intake on the front of the turbo degrades. This allows a small amount of oil to drip onto the swirl flap motor, which is situated directly below. (very poor design). This oil had eventually seeped inside the motor, causing it to short out. This short had instantly popped fuse number 15 under the bonnet, which in turn had caused the engine to shut down while doing 70mph to protect itself. I didn't have the handbook in the car with me sadly, so searching on the internet just have me fuse diagrams of the petrol models, which on those shows its for the injectors. Again as it turns out, fuse 15 in the front fuse box does completely different things on the diesel models. It protects the following.... A/C Clutch, A/C Pressure regulator, Crankcase Vent Heater, EGR Valve, Engine Control Module, Fuel Pump, Glow Plug Module, Swirl Flap Motor, Oxygen sensors..
So I replaced the blown fuse with a spare 20 amp, and the car fired straight up. It was now in limp mode, and showing the EML and Lightening light, but it was drive-able up to about 80 mph, albeit a bit slow getting there.
By this time, the RAC man had arrived. Now there is nothing worse that someone interfering when a pro is at work, so when he arrived, I left him to it, and he plugged the diagnostics in, and it threw up a ton of errors all related to things connected to this fuse. All except the swirl flap motor. He was a bit confused at first, but then I mentioned that I think it might be the swirl flap motor. He hooked up all his testing gear to it, ran a load of tests, and sure enough confirmed to me that the motor was dead.
He then cleared the ECU codes, started the car, and only then did it throw up a specific Swirl Flap related error.
HE gave me some spare fuses, and after a quick road test, we were on our merry way albeit in limp mode.
Now to fixing it.
The cheapest place I could find to supply and fit a new motor quoted £575 plus VAT. The motor is just over £100, but the labour involved is a joke. Anything that is situated inside the VEE of the engine (Swirl Flap Motor, Oil Cooler) etc needs major open heart surgery to fix it. Annoyingly both the motor and the cooler seals have known faults, so they couldn't be in a worse place!
If you fancy forking out all that money to have the motor replaced, then that is no doubt the best way in the long run, however there is a quick fix for £1.99 and YES it does work perfectly.
Get yourself some 4K7 resistors off of ebay, they are £1.99 for 50. Remove the engine cover, then remove the intake pipe that runs from the airbox to the front of the turbo. Right below the turbo, you will see a black box. This is the offending motor. On the right of the motor is a multi plug held in with a grey clip. Remove the metal bracket above the plug, and pop the plug off.
Grab a resistor, and bend the legs in such a way that they will fit snugly into the two centre holes in the plug. Theres 4 in total. Once you have put the resistor in, and you can confirm its in there properly. Tape it up with electrical tape so the resistor wont fall out. Replace the metal bracket, and the air intake pipe, leaving the plug sticking up so you can get to it again in the future if you need to. Then start up the car, and stand back in amazement as both the engine management light and the lightening bolt lights extinguish, and the car comes back out of limp mode.
Take the car for a drive, and you will see that it drives as good as new.
What you have done here, is fool the car into thinking the swirl flap motor is working again. WHen in fact its now disconnected.
You shouldnt notice any difference in performance or fuel economy at all. The emissions may be up slightly when cold is all.
So to summarise, if your car cuts out with the lightening bolt on.
1) Coast to a stop
2) Curse, swear, have a fag, but don't despair
3) Check fuse 15 in the front fuse box, and replace
4) Start the car and drive home in limp mode - The car will do upto 80mph
5) Order your resistors from Ebay, making sure they are the 4K7 type
6) Still use your car while you are waiting for them to be delivered, remembering that it wont pull away as quick as usual
7) Fit the resistor at the weekend in the rain
8) Stand back, chest puffed out, hands on hips, telling the neighbours you've just saved almost 700 quid :-)
- bignev, Eightpint, jack23 and 5 others like this