Emissions

P0471 — Exhaust Pressure Sensor Range/Performance

Severity: medium Drive with care, to a shop

What P0471 means

The engine control unit compares the exhaust pressure sensor signal with what it expects for the current engine speed, load and airflow. P0471 is set when the reading is out of range or does not make sense for the operating conditions. The cause can be the sensor, its wiring or sensing tube, or genuinely high exhaust pressure from a clogged diesel particulate filter or another restriction.

Symptoms

  • Check Engine light on
  • Limp mode with reduced power
  • Loss of power, especially under load
  • Failed or too frequent DPF regenerations
  • Higher fuel consumption
  • Smoky exhaust

Possible causes

  1. Clogged or heavily loaded diesel particulate filter
  2. Failed exhaust pressure sensor
  3. Cracked, blocked or disconnected sensor tubes and hoses
  4. Damaged sensor wiring or connector (open circuit, short to ground or power)
  5. Exhaust leak before or after the filter
  6. Other exhaust restrictions, such as a plugged catalytic converter

How to diagnose

  1. Scan all codes and freeze frame data, and note any related turbo, EGR or DPF codes
  2. Inspect the sensor tubes and hoses for cracks, kinks, soot plugging and moisture
  3. Check the sensor connector and harness for corrosion, chafing and poor contact
  4. Measure sensor supply and reference voltage and compare with specifications
  5. Compare the sensor reading with key on, engine off (should be near atmospheric) and at idle
  6. Check DPF soot load and differential pressure in live data
  7. Inspect the exhaust system for leaks and restrictions
  8. Clear the code and road test or run a forced regeneration to confirm the repair

Common fixes

  • Replace or clear the sensor tubes and hoses
  • Repair the wiring or connector
  • Replace the exhaust pressure sensor
  • Perform a forced regeneration or DPF cleaning, or replace the filter if badly damaged
  • Repair exhaust leaks

Questions and answers

What does P0471 mean?

The ECU sees an exhaust pressure sensor signal that does not match engine operating conditions. The sensor, its hoses, or genuinely high pressure from a clogged filter can be responsible.

Can I drive with P0471?

For a short time, yes, but do not delay. With a clogged DPF the engine may enter limp mode, and continued driving can damage the filter and turbocharger.

How can I tell a bad sensor from a clogged DPF?

Compare the sensor reading with the engine off against atmospheric pressure and inspect its hoses. If the sensor reads correctly but the pressure drop across the filter is high, the filter is the problem.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.