Hi Dan, and 911Hillclimber.
We will be speaking to the Trading Standards people regarding the fact that the Dealers are refusing to carry out the correct diagnosis on a vehicle that is showing electronically that the GPF filter is at 100%.
The fact that our Dealers are using this electronic reading to condemn these filters without checking for back pressure is very suspect.
Regarding Paul's old car, yes its been resold, but we do have the original registration number and chassis number, its in our database.
We have at the moment 3 cars that require a new GPF, at a cost of over 9K. We have asked the Dealers to carry out a back pressure check, only one car is booked in, will update you if it gets done.
Enclose this information for your attention, it just highlights the need for more thorough diagnosis when faced with a suspected blocked GPF.
The motor trade recognized diagnostic path for a suspected blocked Gasoline Particulate Filter (GPF), often referred to as a Petrol Particulate Filter (PPF) or Operating Particulate Filter (OPF), focuses on distinguishing between sensor faults and genuine soot/ash accumulation, followed by forced regeneration or replacement. Because GPFs operate at higher temperatures than diesel filters, they often self-regenerate; therefore, a blockage is frequently triggered by short, city-based driving or faulty exhaust pressure sensors.
1. Initial Diagnostic Scan (OBD-II)
- Retrieve DTCs:Use a diagnostic scan tool (e.g., Snap-on) to look for GPF-specific codes, such as:
- 34D909: High Soot Load Detected.
- 1A280E / 1A280C: PPF (GPF) Pressure Too High.
- 1A2818: Regeneration Interruption.
- P2452 / P2002: Pressure Sensor Circuit or Efficiency below threshold.
- Live Data Analysis: Check "PPF Backpressure" and "Soot Load" values. A high differential pressure reading at idle or during light load indicates a blockage.
2. Physical Inspection
- Sensor Inspection: Inspect pressure sensor pipes for blockages, damage, or moisture. A clogged or leaking pipe can prevent proper sensor readings, causing the ECU to fail to trigger regeneration.
- Borescope Inspection: If the GPF is suspected to be physically damaged or melted (not just blocked), use a borescope (e.g., Snap-on BK700) through a sensor port to check for honeycomb monolith damage.
3. Verification & Diagnostic Test
- Physical InspectionStationary): Use a diagnostic tool to perform a "Service Regeneration" or "Forced Regeneration" to clear minor to moderate blockages.
- Active Driving Test: Perform a "driving regeneration" procedure, where the vehicle is driven at higher loads to increase exhaust temperature to ~600°C to oxidize the soot.
- Differential Pressure Sensor Check: Using a Mityvac or similar tool, apply pressure to the sensor and verify it matches the Live Data in the diagnostic tool to rule out a faulty sensor.
4. Remedy Action
- Clean/Replace: If the soot load cannot be reduced, the filter may require professional off-car cleaning or replacement.
- Initialisation: If the GPF is replaced, you must perform the "Petrol Particulate Filter: Initial Operation" (functional test) on the diagnostic scanner to reset the soot accumulation counter, or the new filter will instantly trigger a warning light.
Common Causes & Symptoms in Trade Practice
- Symptoms: Warning lights, Reduced power/Limp mode, Start-stop function not working, Unusually high fuel consumption.
- Common Cause: Excessive short trips where the engine never reaches optimum operating temperature.
- Wrong Oil: Using oil that does not meet the manufacturer's low-SAPS (Sulphated Ash, Phosphorus, and Sulphur) specification can permanently block the GPF, making it impossible to regenerate.
Points to note:
1. Initial Diagnostic Scan (OBD-11)
We have none of these codes, no pressure, no soot, no sensor codes.
2. Physical Inspection
Because we are not checking for back pressure, the Dealers are assuming that the GPF is definitely blocked.
The only way you can check the GPF core, is to disconnect the rear GPF pipe flange, and check with a very long camera extension.
3. Verification & Diagnostic.
Regarding forced and driving regeneration, this can be done to get rid of soot, but not ash if its physically present in the GPF.
4. Remedy Action
They say they are dealing with Ash, because when they check a GPF thats at 100% and the fault code P242F is present, no soot values are seen electronically.
When these GPF filters or the differential pressure sensors are replaced, they cannot reset the basic setting due to the car not having the adaptation function fitted.
5. Common Causes & Symptoms in Trade Practice
We don't have any issues with reduced power or unusually high fuel consumption.
We do have an issue with the soot regeneration light / message, we never see it, even though the Dealers are saying the GPF is blocked, so were is all the soot going, and why isn't the light / message coming on.
Dont forget we had one of our cars that had covered over 10 thousand miles with the original GPF, that had the DTC P242F, we recorded lots of Ash % checks, and no significant soot was ever recorded. This cars ash values fluctuated between 80 to 100%, over the milege covered.
Regarding the wrong oil being used, this would only be critical if the GPF filters were actually blocked, which they are not.
AND THIS WOULD BE CONFIRMED BY CARRYING OUT A SIMPLE BACK PRESSURE CHECK.
Dave