Limp mode is exactly what it sounds like. The ECU on your Sprinter will detect an error in the turbocharger system. To prevent any possible damages, the ECU will only allow the van to run with greatly reduced power, fueling, and boost. Essentially, it is running only enough for you to limp it home.
Your van may be in limp mode if you notice greatly reduced power with no apparent cause. You will be limited in acceleration, speed, and RPMs. Turning the van off and then restarting the van is a good way to determine if it is in limp mode. If the van runs perfectly even for a few minutes, it is likely in limp mode. It will go back into limp mode unless it is properly diagnosed and fixed. It could go back into limp mode within seconds, or it could take weeks.
There are many reasons for the ECU to think there is a problem. Some are minor quick fixes, and some are much larger and expensive issues. Many jump immediately to a bad turbocharger. Other things should be checked first. If, after diagnosing, there are still a couple of possible culprits, we always recommend starting with the easiest and cheapest fixes.
1. Check your air filter
A dirty air filter can restrict airflow to the engine, leading to a loss of turbo boost pressure. This is especially true if you are unsure when the air filter was last changed. Debris in the air filter housing may also be restricting airflow.
2. Replacing intercooler & turbocharger hoses and seals
As hoses and seals age they are more prone to shrinking and cracking. This can lead to leaks which will cause the turbo to not maintain adequate boost pressure. Any seal or hose in the system could be the culprit but the common ones we see are the turbo outlet seal and the turbo resonator seals. You can visually inspect the seals without removing them initially. If there is an indication that oil or moisture is present on the seal, it is a good indication it is leaking and should be changed. Inspecting the hoses is similar. Any oil or moisture on the hose indicates it could be cracked. You can also try squeezing the hoses with your hands. A hose that feels especially squishy could be leaking. If, after exhausting all sources, you are still unable to find the cause of limp mode, you may need to have the system pressure tested. This is done with a special tool, often by a repair shop.
3. EGR Valve
The EGR valve controls airflow in the exhaust recirculation system and the intake system. The EGR valve should open and close freely. This is pretty easy to remove on a Sprinter. Once removed, you should be able to move it to the open position with your fingers, and it should snap closed when you let go. Because it is constantly exposed to exhaust gasses, it is prone to clogging. If yours is not moving freely, you can clean it so it does move freely and re-install it. Many people can clean and re-install these multiple times before replacing them.
4. Swirl Flap Issues
The swirl flaps inside of the intake manifold control and adjust the airflow. The movement is controlled by the swirl flap motor and swirl rods. All of these components can get clogged by soot. You can try to move the plastic swirl flap rods by hand. They should move freely. If they are stuck, this could indicate the intake manifold should be replaced or cleaned. Likewise, the rods could be broken because the motor was trying to move the flaps, and the stick flaps broke the rods.
If your swirl rods are broken, check out the blog post below and learn how upgrading to metal rods could save you money in repairs.
5. Turbocharger Actuator
Boost pressure to the turbocharger is controlled by a vane system. The vanes are like fan blades controlling the air in the turbocharger. This is controlled by the turbocharger actuator. If the electronic actuator fails when the turbo is still mechanically sound, it can be replaced for a fraction of the cost of a full turbocharger replacement.
You can find a new replacement OM642 actuator here.
6. Blown Fuse
Multiple faulty air sensor codes may indicate that the problem is a blown fuse. If you clear the codes and they reappear immediately before starting the vehicle, it means the sensors are not communicating with the van. This is because they are without power due to the blown fuse. This is especially common after an oil cooler replacement. Check the 15 amp fuse located between the two relays, and we have the replacement fuse available if you need it.
7. Coolant Contamination
This is only applicable to the 4-cylinder OM651 Sprinters 2014-2017. These models can have a water pump failure that causes coolant to migrate into the vacuum system. See this article for more detailed information.
