Your vehicle will automatically enter limp mode after soot build-up has reached high levels to try and prevent further damage to your car. If your Volkswagen enters limp mode, you should immediately take your car to a Volkswagen service centre to run a forced regeneration program to try and save the filter.
The simplest way to sort out a blocked DPF is to engage in 'passive regeneration'. Simply put, this is driving on a motorway or A-road at a sustained speed for 30-50 minutes to allow your exhaust temperature to reach the point where it can cleanly burn off the excess soot.
There are two main types of DPF regeneration: passive and active, however, DPF regeneration can be performed manually using a scan tool.
You can sometimes temporarily override limp mode by restarting the vehicle and refilling the DEF tank. However, you cannot permanently bypass this vehicle feature.
To reset limp mode, first turn off the engine and disconnect the battery for about 15 minutes to clear error codes. Check key sensors like the throttle position sensor and mass airflow sensor for faults. Inspect transmission fluid levels and condition, as low or dirty fluid can trigger limp mode.
How long can you drive a car in limp mode? Limp mode isn't intended to let you keep driving indefinitely because this would be unsafe. Instead, it allows you to reach your destination (if it's relatively close), find a safe place to stop or go to a garage where you can get help.
In such cases, driving five miles to a service center or home likely won't do any damage. However, it's a roll of the dice. If the issue is serious, driving a few miles could cause expensive-to-repair damage. Our general recommendation is, if you find your car in limp mode, pull over and turn off the engine.
Many modern diesel cars will enter limp mode when the DPF filter becomes severely blocked. This reduces the engine's power output to prevent damage. If your car suddenly loses performance and won't accelerate past a certain speed, the DPF could be the issue.
Common Triggers on Today's Diesel Pickups
A full diesel particulate filter, a failed EGR valve, or a bad differential pressure sensor can force a power limit to reduce soot. Fuel rail pressure that is too high or too low can also trigger limp mode.
Continuing to force the DPF to regenerate will worsen the problem and cause serious damage. Injector and Turbocharger Damage: Multiple forced regenerations can overload the turbocharger, fuel injectors as well as other expensive engine components with the extreme heat being generated. This can lead to costly repairs.
So don't ignore it, hoping the DPF light will simply go away. You need to go for a drive where you can get the car up to temperature and keep the revs up - preferably above 3000rpm - for a good few minutes.
A very common way to begin cleaning a DPF is to use high-pressure, compressed air. You can achieve this best by using a high-pressure cleaning cabinet, which backflush compressed air into the filter and forces ash to dislodge any blockage.
Particulate filter regeneration is essential to maintain the performance and efficiency of diesel vehicles. Forcing DPF regeneration may be necessary in some cases, but it should always be done in a controlled manner and with the proper equipment.
If your car has an automatic gearbox, change gears in manual mode, increasing the number of revolutions. However, there's no need to go as far as the rev limiter, as that won't do any good. Drive in this mode for at least 30 minutes. This will trigger a regeneration cycle and your DPF will be cleaned.
You can attempt to bypass limp mode by restarting the vehicle after a short wait. Alternatively, you could try removing one of the battery terminals to reset the electronic systems.
Tackling a turbo's wastegate actuator pivot all too frequently has to be done with decent dose of WD-40® delivered in the 'hit and hope' theory simply by aiming the can with faith it will reach the spot.
In these cases, the DPF must be manually cleaned by adding a cleaning treatment to loosen and dissolve the soot and allow it to pass through the filter. This is done by applying the product through the pressure sensor tube or by removing an oxygen or temperature sensor and applying the product directly to the filter.
Here are the sensors that can cause limp mode to be activated:
Physical damage within the DPF itself, such as cracks or leaks, can prevent the regeneration process from occurring properly. Faulty sensors – The DPF relies on various sensors, including exhaust temperature sensors and differential pressure sensors, to monitor when regeneration is needed.
Limp mode is a car security feature that activates when a fault is detected, reducing speed and switching off non-essential functions. It is triggered by abnormal signals from car components, such as faulty sensors, transmission issues, or low fluid levels.
Sometimes, after the car sits for a while, Limp Mode will clear itself and you can drive again normally.