P244B – Diesel Particulate Filter (DPF) Differential Pressure Too High

Stephen Darby

By Stephen Darby (Contact Me)
Last Updated 2017-03-28
ASE Master Tech

Trouble CodeFault LocationProbable Cause
P244B Diesel particulate filter (DPF) - differential pressure too high DPF regeneration fluid, Large exhaust leaks, DPF pressure sensor, Open or shorted circuit/s

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What Does Code P244B Mean?

When a code P244B is stored, you may assume that the powertrain control module (PCM) has detected an input signal from the circuit of the diesel particulate filter (DPF) pressure sensor indicating that differential pressure is too high. This code is used exclusively in diesel powered vehicles.

DPF systems are used to clean up exhaust emissions in diesel powered vehicles. They remove up to ninety-percent of carbon (soot) from the exhaust. Diesel engines produce black smoke from the exhaust, especially under acceleration. Soot is the main ingredient of the smoke. The DPF filtration element is secured in a steel housing. It resembles a fat muffler or catalytic converter. Positioned ahead of the catalytic converter (and/or the NOx trap), large soot particles are trapped in the DPF element while smaller particles and other (exhaust gas) compounds are allowed to flow through and exit the tailpipe.

Ceramic based cordierite wall fibers are some of the most common elemental compounds that are currently being used in DPF composition. Cordierite is known for its excellent filtration characteristics. It is also known for a tendency to overheat at extreme temperatures, making it susceptible to malfunctions in vehicles equipped with passively rejuvenated DPF systems (see the paragraph below on DPF regeneration systems).

The heart of the DPF is the filtration element. When an excessive accumulation of soot particles takes place inside the DPF, exhaust pressure increases. When exhaust pressure exceeds a predetermined limit, as indicated to the PCM by the DPF pressure sensor, the filtration element must be regenerated. Proper regeneration of the DPF permits exhaust gases to continue flowing through the DPF so that the correct level of exhaust pressure can be maintained.

DPF systems that are regenerated automatically are known as active DPF systems. In this case, the PCM is programmed to inject chemicals (including but not limited to diesel fuel and diesel exhaust fluid) into the exhaust at programmed intervals when DPF pressure reaches a certain level. Under the correct driving conditions, an electronically controlled injection causes the temperature inside the DPF to increase. This temperature increase causes trapped soot particles to burn and be released (through the muffler and tailpipe) as ions of nitrogen and oxygen.

Passive DPF regeneration systems are very similar to active DPF regeneration systems but they typically require some type of manual input. Passive regeneration systems are normally activated when the vehicle is parked and the process may take several hours to accomplish once it is begun.

Once the DPF filtration element is sufficiently regenerated, pressure inside the DPF should drop to an acceptable level.

Plastic DPF pressure sensors are usually mounted away from the extreme heat of the DPF. DPF back pressure is monitored using high temperature silicon hoses (connected to the DPF and the DPF pressure sensor).

 

dpf-sensor

 

If the PCM detects a DPF pressure condition that is higher than programmed parameters, a code P244B will be stored and a malfunction indicator lamp may be illuminated.

What are the common causes of code P244B?

  • Improper DPF regeneration fluid
  • DPF regeneration fluid reservoir may be empty
  • Large exhaust leaks
  • Clogged DPF pressure sensor tubes/hoses
  • Open or shorted circuit/s in the DPF pressure sensor circuit
  • Faulty DPF pressure sensor
  • Driving habits may not be conducive to efficient DPF regeneration

What are the symptoms of code P244B?

  • Diminished engine performance
  • Decreased fuel efficiency
  • Excessive black smoke from the exhaust
  • Increased engine temperatures
  • Increased automatic transmission temperatures

How do you troubleshoot code P244B?

Before diagnosing a code P244B, I need to gain access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source such as All Data (DIY).

Make sure that the vehicle has an adequate amount of the correct reductant fluid or diesel fuel for (DPF regeneration purposes). Codes of this type are often the result of the vehicle being out of reductant fluid or having the wrong type of replacement fluid.

Some driving habits may also contribute to inefficient DPF regeneration (that can cause this type of code to be stored). Many passive and active DPF regeneration systems demand to be driven under heavy loads or at a minimum level of continuous acceleration over a set period of time, before regeneration can be completed.

My diagnosis typically begins with a visual inspection of system harnesses and connectors. Inspect wiring that is routed near hot exhaust components and/or sharp exhaust shields.

I would proceed by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. I like to to write this information down for future reference. I then clear all stored codes and test-drive the vehicle.

If the code is reset, I would use the DVOM (following manufacturer’s recommendations) and test the DPF pressure sensor. Consult your vehicle information source for specific instructions. If the sensor fails to comply with manufacturer’s resistance specifications, it must be replaced.

 

 

bad-dpf-sensor

 

If the sensor complies with manufacturer’s specifications, the DPF pressure sensor supply hoses should be checked for clogs and/or breakage. Replace hoses that are burnt, cracked, or collapsed.

If sensor supply lines are intact, and the sensor checks out, I would begin testing system circuits. To prevent controller damage, disconnect all related controllers prior to testing resistance and/or continuity with the DVOM.

Codes Related to P244B

  • P2452 Diesel Particulate Filter Pressure Sensor “A” Circuit
  • P2453 Diesel Particulate Filter Pressure Sensor “A” Circuit Range/Performance
  • P2455 Diesel Particulate Filter Pressure Sensor “A” Circuit High
  • P2456 Diesel Particulate Filter Pressure Sensor “A” Circuit Intermittent/Erratic
  • P2458 Diesel Particulate Filter Regeneration Duration
  • P2459 Diesel Particulate Filter Regeneration Frequency
  • P2461 Diesel Particulate Filter Pressure Sensor “B” Circuit High
  • P2462 Diesel Particulate Filter Pressure Sensor “B” Circuit Intermittent/Erratic
  • P2463 Diesel Particulate Filter Restriction – Soot Accumulation

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