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P2002 – Diesel particulate filter efficiency below threshold (Bank 1)

What it means

The diesel particulate filter (DPF) traps soot from the exhaust and burns it off from time to time at high temperature. This is called regeneration. The computer uses a differential pressure sensor to watch the pressure before and after the filter. P2002 means the filter isn't behaving as expected. Often the pressure difference is suspiciously low, which suggests a damaged or missing filter element, but a sensor or hose fault can also be behind it. Exactly what is monitored varies by model.

Symptoms

• Check engine light or DPF light on.
• Sometimes loss of power or limp mode.
• Less often, a sooty tailpipe or visible smoke.
• Often no symptom except the code.

Common causes (most likely first)

1. A faulty differential pressure sensor, or a bad signal.
2. A cracked, loose or blocked sensor hose between the filter and the sensor.
3. A damaged, cracked or burnt-out filter element that lets soot through.
4. A heavily clogged, overloaded filter, if the computer also reports that with this code.
5. A related engine fault (injectors, EGR, turbo) producing too much soot.

How urgent is it? Can I drive?

Usually drivable in the short term, but don't put it off. An overloaded filter raises exhaust back-pressure and can trigger limp mode, and over time the engine and turbo can suffer. If the DPF light is on and there is no power loss, a longer steady drive on open roads can help it regenerate. Your owner's manual explains what to do for your model.

What to check first

1. Read all codes. Fix any injector, EGR or turbo codes first.
2. Watch the DPF differential pressure in live data at idle and when revving. If it doesn't change with throttle, suspect the sensor or a hose. If it is very low even at high rpm, the filter may be damaged.
3. Inspect the sensor's rubber hoses for cracks, loose ends, melting or water inside.
4. If your scanner shows it, check the soot load and when the last regeneration ran.

When to see a mechanic

If the sensor and hoses are fine, the filter needs to be checked in a workshop. Forced regeneration, cleaning or replacement should only be done there. Removing, gutting or coding out the DPF is illegal, and we don't help with it. A car like that can also fail its roadworthiness test.

FAQ

Will a regeneration fix P2002?

It can help if the filter was just overloaded. It won't if the sensor, a hose or the filter element is damaged.

Is replacing the sensor enough?

Only if testing shows it is faulty. Check the hoses first, because they are often the cause.

Can short city trips cause DPF faults?

Yes. On short trips the filter doesn't get hot enough to regenerate and fills up faster.