Diesel Particulate Filter Pressure Sensor "A" Circuit Range/Performance

What it means

The diesel particulate filter (DPF) differential pressure sensor is sending a signal that is electrically valid but does not make sense compared with other sensors. The diesel particulate filter (DPF) differential pressure sensor measures the pressure drop across the DPF so the ECU knows how full of soot it is and when to regenerate. This usually points to a sensor that is reading wrong, or to a real mechanical problem it is reporting correctly, rather than a broken wire.

Symptoms

• Check engine light on
• DPF warning light
• Frequent or failed regenerations
• Reduced power (limp mode)

Probable causes

Most likely first

1. 1Cracked, melted or swapped sensor hoses
2. 2Blocked sensor ports
3. 3DPF actually blocked
4. 4Failing sensor giving an inaccurate reading
5. 5Poor connection at the sensor connector

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the diesel particulate filter (DPF) differential pressure sensor connector and wiring (on the engine or firewall with two small hoses running to the DPF). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the diesel particulate filter (DPF) differential pressure sensor reading on live data. With the engine off it should read about 0. At idle it should be low and rise with engine speed.
4. 4Compare the diesel particulate filter (DPF) differential pressure sensor reading against related sensors and the real-world condition. If they disagree, find out which one is telling the truth before buying parts.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Fix the underlying problem the sensor is reporting, if real
• Replace the diesel particulate filter (DPF) differential pressure sensor if it reads wrong against a known-good reference