OM656 -DPF Sensor 1 EGR Low Pressure Signal Offset Fault

System: Engine Management / Emissions
Component: Differential Pressure Sensor for Low Pressure EGR
Part Reference: A000 905 11 19
Engine: OM656

Fault Code : P238328 – Differential pressure sensor 1 for exhaust gas recirculation (low pressure): signal offset outside the permissible range (STORED / MIL ON )

Typical Symptoms

• Engine warning light illuminated
• Fault stored in engine control unit
• Possible reduced EGR system efficiency
• In some cases no noticeable drivability issues
• Vehicle may enter limp mode if the fault persists or sensor readings become implausible

Possible Cause

• Internal sensor calibration drift
• Faulty differential pressure sensor
• Sensor contamination caused by exhaust soot
• Damaged pressure hoses connected to the sensor
• Wiring or connector issues affecting signal accuracy

Diagnostic Insight

This fault indicates the sensor signal offset is outside the permissible range stored in the engine control unit. The ECU uses this sensor to determine exhaust gas flow within the low-pressure EGR system.

Technicians usually check:

• live data readings from the differential pressure sensor
• pressure hose condition and blockages
• wiring integrity and connector condition
• signal plausibility compared with expected exhaust pressure values

If the signal offset remains outside specification, the sensor itself is often the root cause.

In this case, replacement of the differential pressure sensor A000 905 11 19 restored normal system operation and the engine warning light cleared.

Professional Diagnostic Recommended

Accurate diagnosis of EGR pressure signals requires manufacturer-level diagnostic equipment.