The car is in limp mode with three warning lights on the dash – a situation that can scare any driver!
When starting the engine, three warning lights come on: the engine management light, the DPF light and the glow plug light. The glow plug and engine lights indicate that the engine is running in limp mode, has reduced power, does not rev up completely, and even when it does rev up, it is very slow.
Limp mode is a self-preservation feature that protects your engine and transmission from catastrophic failure.
Car diagnosis for faults
During the vehicle scan, we found a particulate filter fault.
The fault indicated a particulate filter restriction; the filter was clogged and required regeneration.
We have spoken with the customer and got the history of driving. The customer advised that he barely drives on a motorway, only driving in the city for short journeys that don’t help on the particulate filter. As known, a particulate filter needs driving for at least 40 minutes at more than 40 mph to perform regeneration.
We have read the data from the particulate filter to understand how badly clogged it is.
Usually, a DPF filter that needs regeneration has an excess pressure of 40hPa. The diagnostic tool indicates that the pressure was 9hPa, so the filter was not as bad as expected by looking at the warning lights.
We have found the guilty party
One of the problems with these cars is the DPF pressure sensor (photo below), which sometimes fails and provides wrong readings. Intermittently, it gives a higher reading than it is, and it is easy to believe that the particulate filter is clogged when it is not.
To understand better, when the particulate filter light comes on on these cars, you have to drive the vehicle on the motorway for at least 40 minutes of continuous driving at high speeds, and the particle filter regenerates itself.
A stop en route often interrupts the regeneration process. If this happens several times, the other two warning lights (glow plug and engine light) appear, and the engine enters limp mode. At this point, the regeneration can only be done in a workshop with the diagnostic machine.
The car isn’t in limp mode anymore
Replacement of the DPF pressure sensor completed. We cleared the error; the glow plug and the engine warning lights were gone off.
After resetting the particulate filter error, the car was no longer in limp mode.
Regeneration needed to resolve the last problem
We drove it in the motorway to carry out a regeneration procedure. The temperature in the filter reached between 450 to 500-550 degrees.
Work has been completed
At the end of the process, the particulate filter warning light went out.
Work completed, all the lights are off, and the DPF problem is resolved.
You can see the entire procedure in this video: