Fuel and air

P0235 — Turbo/Supercharger Boost Sensor A Circuit Malfunction

Severity: medium Drive with care, to a shop

What P0235 means

The engine control module reads boost sensor A to know how much pressure the turbocharger or supercharger is making. It uses this signal to manage fuel, boost control and the wastegate. When the signal is out of range or doesn't make sense, the module can't control boost accurately and usually cuts power.

Symptoms

  • Check Engine light on
  • Reduced power and sluggish acceleration
  • Limp mode
  • Hesitation when accelerating
  • Poor fuel economy
  • Whining or hissing noises if there is a boost leak
  • Related underboost or overboost codes

Possible causes

  1. Failed boost pressure sensor A
  2. Damaged wiring or corroded connector at the sensor
  3. Open circuit or short to ground or power in the harness
  4. Wiring damaged by heat near the turbo
  5. Boost hose or vacuum line leak skewing readings
  6. Wastegate actuator or turbo mechanical problem
  7. Internal ECM fault or software issue (rare)

How to diagnose

  1. Scan all codes and freeze-frame data and note any related boost codes
  2. Inspect the sensor connector and harness for heat damage, chafing and corrosion
  3. Check boost hoses, clamps and vacuum lines for cracks, loose fittings and oil residue
  4. Compare live boost reading with barometric pressure key-on engine-off, then with the specified boost under load
  5. Measure the 5 V reference, ground and signal wire continuity at the sensor connector
  6. Test the sensor signal with a multimeter or scope as load changes
  7. Check wastegate or boost actuator movement through its full range
  8. Consider the ECM only after the sensor and wiring are ruled out

Common fixes

  • Replace boost pressure sensor A
  • Repair or replace damaged wiring and connectors
  • Fix leaks in boost hoses and vacuum lines
  • Repair or replace the wastegate actuator or turbo if confirmed faulty
  • Reflash or replace the ECM if an internal fault is confirmed

P0235 on different brands

Ford · manuals
On Ford, the extended format P0235:16 means the boost sensor A circuit voltage is below the threshold, which describes the monitor condition detected rather than a confirmed failed part.

Questions and answers

Can I drive with P0235?

For a short time, yes, but power is usually limited. Bad boost data can stress the turbo, so get it diagnosed soon.

What most often causes P0235?

Most often it is the boost sensor itself or a wiring or connector problem, especially near hot turbo parts. Boost leaks can cause similar symptoms.

Will the code clear itself?

The light may go out if the fault doesn't recur over several drive cycles, but the cause remains. If it isn't fixed, the code will likely return.

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.