Powertrain, generic · Fuel and air metering (injector circuit)

P0235 Turbocharger/Supercharger Boost Sensor A Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Boost sensor A measures the absolute pressure between charge air cooler and throttle – GM calls it TIAP, Ford TIP – usually combined with an intake air temperature sensor; its voltage rises with pressure. With the ignition on and the engine stopped it must read the same as manifold and barometric pressure. P0235 is the general fault of sensor A's circuit or signal, for modules that do not split low, high and range. GM, Ford and Saab do not use it; Audi documents it on the Q7 TDI together with over- and underboost, so there it also marks an implausible boost value, for example from a charge air leak or jammed turbo vanes. No manufacturer threshold for this code was found. With a sensor fault boost control is switched off and only the base boost of the wastegate spring remains, with a clear loss of power.

Likely causes

Connector at the boost sensor corroded or loose, broken wire
Boost sensor faulty, often oily from crankcase ventilation
Charge air leak or jammed turbo vanes causing an implausible value
5 V reference shorted by another sensor

Symptoms

  • Check engine light on
  • Clear loss of power, only base boost
  • Boost reading implausible in a scan tool

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–250
Time0.5–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

boost pressure sensor asensor wiringcharge air hoses

Related codes

P0236P0237P0238P025EP0239P0105

References: law.cornell.edu, static.nhtsa.gov, saabwisonline.com, en.wikipedia.org.