Fuel and air

P025E — Boost Pressure Sensor 'A' Signal Intermittent or Erratic

Severity: medium Drive with care, to a shop

What P025E means

The engine control module constantly compares the boost pressure sensor signal with the value expected for the current load and RPM. P025E sets when that signal drops out, jumps around or does not match how the engine is running. The usual culprits are the sensor itself, a poor connection at its connector, damaged wiring, or less often a leak in the charge-air system.

Symptoms

  • Check Engine light on
  • Loss of power and hesitation when accelerating
  • Surging or rough running under load
  • Unstable boost readings on a scan tool
  • Occasional rough idle
  • Limp mode with reduced power
  • Possible unusual turbocharger noise

Possible causes

  1. Failed boost pressure sensor
  2. Open, short or corroded wiring or connector at the sensor
  3. Poor ground or unstable 5 V reference voltage
  4. Charge-air leak: hoses, clamps, intercooler
  5. Leaking or damaged vacuum lines
  6. Turbo actuator or position sensor fault, or sticking variable geometry mechanism
  7. ECM fault (rare)

How to diagnose

  1. Read all codes and freeze-frame data, noting when the fault sets
  2. Inspect the sensor, connector and harness for corrosion, chafing, broken wires or oil in the connector
  3. Wiggle the harness and connector with the engine running while watching the sensor reading
  4. Check the 5 V supply and ground at the sensor connector
  5. Compare boost in live data with ambient pressure at key-on engine-off, then with the target under load
  6. Inspect charge-air hoses, clamps, intercooler and vacuum lines, and pressure test if needed
  7. Check turbo actuator or variable geometry movement through its full range
  8. If everything checks out, evaluate the ECM and its software

Common fixes

  • Repair the wiring or replace a damaged connector
  • Replace the boost pressure sensor
  • Fix charge-air leaks and replace damaged hoses
  • Repair or replace the turbo actuator, or free up the variable geometry mechanism
  • Reflash or replace the ECM as a last resort

Questions and answers

Can I drive with a P025E code?

For a short trip to a shop, carefully, yes. The engine may lose power or go into limp mode, and incorrect boost control puts extra stress on the turbo and engine.

Will replacing the boost sensor fix P025E?

Not always. The sensor is a common cause, but check the connector, wiring, power and ground, and look for air leaks first. Otherwise the code can come back.

Can I just clear the P025E code?

You can, but if the cause is still there the code will return. With an intermittent fault it is especially important to find the bad connection or damaged wire.

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.