P0472

What P0472 Means

Code P0472 indicates a low signal from the exhaust pressure sensor. This sensor measures exhaust gas pressure, which is required for correct operation of the exhaust gas recirculation (EGR) system, the diesel particulate filter (DPF), and the turbocharger. A low signal can come from a failed sensor, an open circuit or poor contact in the wiring, or a problem with the reference voltage.

The engine management system (DME/DDE) uses the sensor reading to calculate load and control DPF regeneration. When the signal falls outside the allowed range, the control unit sets the fault and may enter limp mode to protect the components.

Symptoms

• The Check Engine light comes on (DDE-Lampe).
• The engine may drop into limp mode (Notlauf) with reduced power.
• Refitting the sensor can trigger a companion fault LMM P0115C, which also switches on the DDE-Lampe immediately and puts the engine in Notlauf.

Diagnosis and Repair

1. Read the fault codes with diagnostic equipment (ISTA, INPA) and check for companion faults such as P0115C.
2. Check the exhaust pressure sensor: inspect the connector and wiring harness for open circuits, corrosion, or damaged insulation.
3. Check the reference voltage and signal circuit with a multimeter to the manufacturer's specification.
4. Replace the sensor with a known-good unit if needed.
5. Clear the codes after replacement and take a test drive to confirm the fault doesn't return.

Common diagnostic mistakes: replacing the sensor without checking the wiring won't fix the problem if the cause is an open circuit.

Related Problems

Ignoring P0472 can lead to the following:

• A companion fault LMM P0115C after refitting the sensor, which switches on the DDE-Lampe immediately and puts the engine in Notlauf.
• Heavy soot deposits around the DPF-to-turbocharger joint and on the front side of the turbocharger, which can point to disrupted regeneration and elevated exhaust pressure.
• Running for a long time with a failed sensor can damage the DPF and turbocharger through incorrect regeneration control and overheating.

Don't put off the repair — fixing it now prevents an expensive failure later.