P2002: Diesel Particulate Filter Efficiency Below Threshold (Bank 1)

Can I keep driving?

What to do right now

1. 1Check your instrument cluster for any red warning lights, flashing engine lights or limp-home mode messages.
2. 2Avoid heavy acceleration and long motorway trips until you have checked the exhaust and sensor pipes.
3. 3Arrange an OBD scan or visit a garage soon to read live exhaust pressure data and find out whether it is a cheap pipe or sensor fault.

Likely causes

Most likely first.

1. Likely

   Cracked or damaged internal DPF ceramic core

   Extreme heat during an aggressive regeneration cycle or road debris hitting the exhaust can crack the fine internal ceramic substrate, allowing soot straight through.

2. Possible

   Split or melted pressure sensor rubber hoses

   Small rubber hoses running between the exhaust and the differential pressure sensor perish, split or melt from heat, leaking exhaust pressure to the atmosphere.

3. Possible

   Faulty DPF differential pressure sensor

   Internal sensor degradation or moisture ingress creates incorrect voltage readings that trick the engine computer into calculating incorrect pressure drop across the filter.

4. Rare

   Exhaust gas leak before the filter

   A cracked flexi-pipe, blown gasket or loose clamp upstream of the filter allows exhaust gas to escape before it reaches the pressure measuring points.

5. Rare

   Tampered or gutted particulate filter

   A previous owner or garage may have deliberately cut open and emptied the ceramic filter core to avoid replacement costs, causing zero backpressure.

What you can check yourself

Park somewhere safe and level, engine off, before you start.

1. 1

   Wipe the exhaust tailpipe

   With the engine cold and switched off, wipe a clean white paper towel inside the tip of the exhaust tailpipe. A thick layer of black soot points to a cracked internal filter core, as an intact filter leaves the exhaust clean.

2. 2

   Inspect the pressure sensor rubber hoses

   Open the bonnet and locate the differential pressure sensor on the bulkhead, then follow its small rubber and metal pipes down toward the exhaust. Check along the rubber sections for splits, chafing, heat damage or loose push-fit connectors.

3. 3

   Check for exhaust soot under the bonnet

   With the engine bay cool, look around the turbocharger and exhaust manifold area using a torch. Fresh black soot dusting or a strong smell of diesel exhaust indicates a pre-filter leak.

4. 4

   Scan for other engine fault codes

   Plug in an OBD code reader to see if related fault codes appear alongside P2002. Accompanying codes for exhaust gas recirculation or exhaust gas temperature sensors can help identify what triggered the filter failure.

Typical prices in Ireland (€) and the UK (£), from an independent garage up to a main dealer. The total repair cost depends heavily on whether the fault is simply a split rubber sensor hose or a cracked internal filter core that requires complete replacement.

When to go to a garage

• Book a garage visit if you find black soot inside the tailpipe, as a cracked ceramic core means the filter needs replacing.
• Go to a mechanic immediately if the engine light begins flashing or the car enters limp-home mode with reduced power.
• Contact a specialist if replacing the sensor and checking the hoses does not clear the fault code after a software reset.

Questions drivers ask

Test rules here are for the National Car Test in Ireland (NCT) and the MOT in the UK. Elsewhere, check the regulations of your own country or state before going for a vehicle test.