What it means
The module detects that the signals from particulate filter pressure sensors A and B do not correlate as expected. This indicates inconsistent readings, but does not identify which sensor or circuit is at fault.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The control module compares the readings from DPF pressure sensors A and B to check whether they agree in the expected way. P246D sets when their signals do not correlate; it does not identify which sensor, hose, or circuit is responsible.
Common causes
Most likely first.
- Faulty or drifted pressure sensor A or B
- Blocked, leaking, or damaged pressure-sensor hose
- Wiring or connector fault affecting either sensor
- Exhaust leak or restriction affecting pressure readings
Symptoms
- Check engine light or DPF warning light on
- Power loss / limp mode
- Increased fuel consumption
- Failed forced regeneration attempts
How to diagnose it
- Read freeze-frame data and related DPF codes to see when the A and B readings diverged and whether regeneration was active.
- Compare live readings from pressure sensors A and B under the manufacturer's test conditions to confirm the mismatch.
- Inspect both sensors' hoses for blockage, leaks, cracks, kinks, or swapped connections that could make their readings disagree.
- Check the connectors and wiring for both sensors for corrosion, looseness, heat damage, or chafing.
- Test each sensor and its circuit separately using the manufacturer's procedure to determine whether one signal is inaccurate.
- Inspect for an exhaust leak or restriction affecting pressure readings, then confirm the A/B readings correlate after repairs.
Common fixes
- Reconnect or correctly route the A and B pressure-sensor hoses.
- Clear blocked hoses or replace cracked or leaking hoses.
- Repair damaged or corroded wiring and connectors for the affected sensor.
- Replace sensor A or B only if testing shows its reading is inaccurate.
- Repair an exhaust leak or restriction that is distorting the pressure measurements.
Can I keep driving?
If the vehicle has reduced power or a DPF warning, avoid heavy loads and long trips until the sensor disagreement is diagnosed. Incorrect pressure feedback can prevent regeneration or hide worsening filter restriction.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.