Diesel Particulate Filter Soot Content Fault – OM651
System: Engine Management / Emissions
Component: Diesel Particulate Filter (DPF) Monitoring System
Engine: OM651
Fault Codes:
• P246309 – The soot content of the diesel particulate filter is not OK (component fault – current and stored, MIL ON)
• P245328 – Differential pressure sensor 1 in the diesel particulate filter: signal offset outside the permissible range
Typical Symptoms
• Engine warning light illuminated
• Possible reduced engine performance
• Regeneration process may fail or occur more frequently
• Increased fuel consumption
• Vehicle may enter limp mode if soot load exceeds calculated limits
Possible Cause
• Faulty differential pressure sensor
• Sensor signal offset outside permissible range
• Blocked or damaged pressure hoses connected to the sensor
• Excessive soot accumulation in the diesel particulate filter
• Incomplete or interrupted regeneration cycles
• Electrical wiring or connector issues
Differential pressure sensor (A0009051119)
Diagnostic Insight
The engine control unit uses the differential pressure sensor to calculate the soot level inside the diesel particulate filter.
If the sensor signal offset is outside the permissible range, the ECU cannot correctly determine soot load. This can trigger the engine warning light and store fault codes P246309 and P245328.
Technicians usually check:
• differential pressure sensor live data
• pressure hoses for blockage or soot contamination
• wiring and connector condition
• calculated soot load of the diesel particulate filter
If the sensor signal is implausible, the differential pressure sensor should be replaced first.
After the repair, a guided regeneration test may be required to reduce soot accumulation in the diesel particulate filter.
Some OM651 vehicles produced after 2011 may also require an engine control unit software update.
Professional Diagnostic Recommended
Modern Mercedes-Benz systems are complex and require specialist diagnostic equipment. If this fault is present, the vehicle should be inspected by a Mercedes-Benz dealer or a qualified Mercedes specialist who can perform the correct diagnostic tests and software procedures. Information on this page is provided for reference only and should not replace professional diagnosis.
