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

P0238 Turbocharger/Supercharger Boost Sensor A Circuit High

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. P0238 means the signal voltage is above its upper limit: GM above 86 % of 5 V (about 372 kPa) for roughly 4 s with the warning light in the first trip, Ford above 4.88 V for 5 s, Saab's 1.6 turbo above 4.8 V. Causes are a signal shorted to 5 V or 12 V, an open sensor ground or – on GM modules with a pull-up input – an open signal wire. If several high codes appear at once, check the shared ground. 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

Sensor ground open, or signal wire open on a pulled-up input
Signal shorted to 5 V or 12 V
Sensor faulty internally
Connector corrosion or moisture at the ground
Engine module

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€30–200
Time0.3–1.5 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

P0237P0236P025EP0235P0242P0108

References: law.cornell.edu, gsi.ext.gm.com, fordservicecontent.com, newtonnet.co.uk.