Diagnosing DPFs

Dave Falconer examines diesel particulate filter systems and how they can be diagnosed

Published:  11 August, 2014

By Dave Falconer, Diagnostic Product Specialist at Snap-on

There are three different regeneration modes to clear the soot in the DPF:

Passive Regeneration takes place while driving when engine load elevates exhaust temperatures enough to burn small amounts of soot. These temperatures can range from 200ºC to almost 600ºC and requires no action from the driver or engine control system.

Active Regeneration can occur while driving or when the vehicle is not moving and the engine is idling, to burn large amounts of soot. The process is initiated by the engine management control module software and only when certain conditions are met. Typical exhaust temperatures will range from around 400degC to over 600degC and requires no action from the driver.

Manual Regeneration is essentially the same as active regeneration but is initiated by using a scan tool. There are two modes of manual regeneration - static and dynamic. Static is when the vehicle is stationary but due to the very high temperatures around the DPF, this could risk damaging wiring and other components. Many manufacturers are now disabling static regeneration, as driving the vehicle allows airflow under the vehicle to cool wiring and components close to the DPF.

DPF over 90% filled. This requires replacement of the DPF and will require a scan tool to reset DPF values in engine management control software after the new DPF has been fitted.

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