Imagine you’re driving along the roads in the beautiful country around Nanaimo, BC. You intend to merge onto Highway 19, but when you try to accelerate, your Sprinter van simply won’t give you the juice you need.
You put your pedal to the floor…and still nothing. You can’t even get above 80 kph. Your Mercedes-Benz vehicle is likely in what’s called limp mode. Here’s what you need to know about what causes this setting and what to do if the scenario above happens to you.
Photo by Jonathan Arbely on Unsplash
What Is Mercedes Sprinter Van Limp Mode?
Limp mode is also often called “limp home mode” or LMH. As the name implies, it’s a setting that makes it possible to limp home but not much else. Limp mode is used in other turbocharged diesel vehicles, but it’s most commonly associated with Sprinter vans.
The limp mode setting was incorporated into the Mercedes-Benz Sprinter as a protective mechanism. It keeps drivers from going fast or putting too much stress on the engine when there is a problem, thereby preventing overheating and other catastrophic consequences. One way it does this is by shutting off the turbo.
How Can You Tell If You’re Probably in Limp Mode?
Not sure if your vehicle is in limp mode? Look for these signs:
- Inability to reach highway speeds (usually limited to about 80 kph or less)
- Difficulty going up steep hills
- Limited RPMs (typically under 3,000)
- Transmission won’t shift into third gear or above
- Sluggish acceleration and poor responsiveness
- Engine whining or whirring loudly
- Black smoke coming from the exhaust
- Check engine light illuminated (flashing or solid) on the dashboard
You may see other alerts on the instrument panel. You may be able to restart the van if you stop and let it cool off a bit, but the same symptoms will return again if you try to push the engine too far.
Mercedes Sprinter Limp Mode Causes
So, what causes a Sprinter van to go into limp mode in the first place? As we mentioned above, this is a protective feature, not a bad thing, in spite of it being an inconvenience. There are multiple reasons why a Sprinter van may go into limp home mode.
Clogged Air Filter
This is the easiest thing to check first, and it’s a common engine problem. When your engine is deprived of air, it makes combustion difficult. And it affects the ability of the turbocharger to provide additional pressure.
Cracked Hose
Both turbocharger and intercooler hoses can develop cracks over time. Your diesel mechanic can check the latter with an intercooler pressure tester to find leaks you might miss visually.
Blown Fuse
Your air sensors need power to function properly. But a blown fuse can cut their power. Your mechanic will look for air sensor codes that can’t be cleared until the right fuse is replaced.
Faulty Turbo Actuator
Turbochargers function similarly to pumps, with fan-like vanes inside that move air. If the actuator that controls the vane system electronically fails, it can be replaced without having to replace the entire turbo.
Swirl Flap Problem
The swirl flap system is part of the intake manifold, but it can get gunked up with soot. Cleaning or replacing this part may be the solution.
Bad EGR Valve
The exhaust gas recirculation (EGR) valve is part of your exhaust system. It affects emissions and also air intake. It may not be opening or closing properly, requiring cleaning. Or there may be an electrical problem, which usually points to needing a replacement.
Low Transmission Fluid
Transmission fluid lubricates your transmission components. It’s possible that your fluid is so low that the limp mode gets triggered, preventing you from upshifting into third gear. Occasionally, the clutch may also be to blame in manual transmission vehicles.
Other Possible Problems
Some other potential issues with the van that appear less often could be:
- Worn or damaged catalytic converter
- Faulty oxygen sensor
- Bad mass air flow (MAF) sensor
- Worn transmission gears
You Have a Sprinter Van Stuck in Limp Mode: Now What?
It’s important to get your Sprinter van to your mechanic if you believe you’re in limp mode or if one of your fleet vehicles shows signs. Do not attempt to keep driving for days in limp mode.
You may be able to drive to your diesel garage if you’re not too far away. But if you’re any distance from the shop, it’s best to arrange for a tow, especially if the check engine light is flashing, not solid.
Your mechanic can run the computer codes for your Sprinter van and get to the bottom of what’s going on. It’s possible that you’re not actually in limp mode and have another problem. Either way, the shop can diagnose and fix your van and get you back on the road again safely.