“Limp Mode” or “Limp Home Mode” is a condition that can affect turbocharged diesel vehicles. Your Sprinter’s ECU senses something malfunctioning in the turbocharger system–either reading too much boost, too little boost, etc.–and decides puts the van into low power or “limp home mode”. Limp home mode has little to no turbocharger pressure and vastly reduced fueling, and the engine is only making a fraction of rated power. The easiest way to identify “limp home mode” is that you can restart your van and the power will return – maybe for a few days or even just a few miles. This is common condition with a few common causes.
Symptoms of “Limp Home Mode”
- Sudden Drop in Power without any “noise” or indication something went wrong
- Low power – enough power to get to 50 mph in some cases, but not to keep that speed up a hill.
- 3,000 RPM rev limit – some models limit the engine to 3000 RPMs when in limp-home mode
- Able to be “reset” by restarting vehicle
1. First off, it isn’t a “Bad” Turbocharger
We most often hear of “limp home mode” being diagnosed as a faulty turbocharger, and, accordingly dealerships and service centers replace the turbo for thousands of dollars.Unfortunately, this could end up being a monumental waste of money. Limp home mode is more often caused by things other than the turbocharger, things that are vastly less expensive than replacing the turbocharger itself.
1. Occam’s razor: Check the Air Filter
The easiest solutions are often the best solutions, so, always check your air filter first before digging into other problems. A clogged air filter can chose the engine of air and result in inadequate turbocharger boost pressure. Air filters are cheap and, on Sprinters, very easy to replace. Plus, a new air filter never hurts!
2. Check Intercooler & Turbocharger Hoses
Sprinter Intercooler hoses are prone to leaks. A leaking hose will cause limp mode as the vehicle will be unable to maintain specified boost pressure. The most often leak occurs at the fittings where hoses attach to hard pipes or the intercooler. Any buildup of black “gunk” near a fitting is an indication it is leaking. Replace the intercooler o-ring seals or refresh the hoses themselves to fix any leak you find.
Any curved hose is also a candidate for developing a split. Check all sides of all curved hoses by squeezing the hose vigorously. These hoses expand when pressurized, so a crack or split may not be noticeable if the hose isn’t under pressure. Replace any hose that has a crack in it. Trying to repair the hose is unlikely as oil vapors will break down any adhesive used to make a repair.
If a visual inspection doesn’t reveal a clear leak but you still suspect one may be the problem, investing in an Intercooler Pressure Tester may be a good idea. These devices allow you to pressurize the intake and intercooler system and find any leaks you may have.
3. Faulty EGR valve
If the EGR valve isn’t opening and closing at the correct time due to a mechanical issue, or it has an electrical fault, the vehicle will go into limp mode. Try cleaning your EGR valve first to see if you can restore proper motion. If that does not help, you’ll need to install a new EGR valve. Luckily the EGR valve on Sprinter models is located at the top of the engine and is easy to replace.
4. Swirl Flap Issue
The intake manifolds have flaps to direct airflow during different RPM and load situations. The swirl flap servo motor is a common failure item. Always replace the swirl flap clips when replacing the motor.
5. Turbocharger Actuator
On the modern diesel engine used in the Sprinter van, boost pressure is controller using a vane-system. The control valve for the vane system is electronically controlled and can fail. The turbocharger is still healthy, only the control valve has failed. Unfortunately, replacement actuators aren’t available new from Mercedes or from the turbocharger manufacturer. However, pull the part number off the actuator in your van and call your favorite used parts supplier to see if they have any in stock. You might be able to pick one up cheap.
Causes of Limp Mode on Pre 2007 Sprinters:
Turbo Actuator: We don’t offer this item separately, but often times the turbo isn’t working correctly because the electronic actuator is broken. Pre 2007 turbochargers can have their actuators adjusted.
Turbo Resonator: Common failure part on these vehicles. Can replace with a durable aluminum unit to fix the faulty factory part.
Turbo Actuator Electric Vacuum Control Valve or Air Sensors: The Turbo Actuator Electric Vacuum Control Valve is a small solenoid valve that regulates boost pressure. If this is broken your vehicle will probably go into limp mode. Two other sensors, the Charge Pressure Sensor and Air Intake Pressure sensor, will also cause the vehicle to go into limp mode if they are faulty.
Here are some codes related to Limp Mode:
P0299: Turbocharger Underboost
P2953: Intake Swirl port actuator open/sensor value too low
P0401/P0402: Exhaust Gas Recirculation Flow Excessive
We have a full list of parts for Sprinters on our website IDParts.com.