Code P0238: high signal from the turbo pressure sensor

Original definition (SAE J2012): Turbocharger Boost Sensor A Circuit High^[1][2][3]

1. 1Faulty boost pressure sensor.^{[1][2][3][4][5]}
2. 2Damaged sensor wiring or connectors: open circuit, short to the supply, or a fault in the sensor's 5 V supply or reference earth.^{[1][2][3][4][5]}
3. 3Boost pressure that really is excessive, according to Autodoc Club: stuck wastegate or faulty wastegate control unit, or a faulty turbo control flap.^[1][2]
4. 4Faulty engine control unit or one with software errors.^[1][2]
5. 5Other mechanical causes that Autodoc Club includes in its list: leaks in the pressure hoses, a blocked or damaged intercooler, a blocked air filter or mechanical defects in the turbo.^[1][2]

• Engine warning light on in the instrument cluster.^[4]Engine warning light: faults that cause it
• Loss of power and poor acceleration.^[1][2][5]Less power: faults that cause it
• The engine goes into limp mode, with power limited.^[1][2][5]Limp mode: faults that cause it
• Irregular engine running or jerking when accelerating.^[1][2]Jerking: faults that cause it
• Unusual noises, such as whistling, in the engine bay.^[1][2]Turbo whistle: faults that cause it
• Dark smoke from the exhaust.^[1][2]Black smoke: faults that cause it
• Fuel consumption noticeably higher than usual.^[1][2]Uses more fuel: faults that cause it

1. 1Read all the stored codes and use the diagnostic equipment to compare the pressure given by the boost sensor with atmospheric pressure and with that of the MAP sensor: they should be consistent with each other.^[5]
2. 2Inspect the intake duct and the sensor wiring for damage, leaks, dirt or blockages, and repair any damaged wiring.^[1][2][5]
3. 3Disconnect the sensor and measure the reference earth at the connector and, with the ignition on, the 5 V supply; the Saab manual gives reference values of less than 5 Ω to earth and between 4.8 and 5.2 V. Ross-Tech publishes, for a VW Tiguan 2.0 TSI, voltages measured at the connector with the sensor disconnected and connected.^[4][5]
4. 4Check the signal: with the sensor disconnected, the diagnostic equipment reading should be high (more than 275 kPa in the Saab manual) and, when you bridge the signal and the reference earth with a jumper wire, it should drop to almost zero (less than 1 kPa). This is how to tell a wiring problem from a faulty sensor.^[5]
5. 5If the circuits are fine, test or replace the sensor.^[1][2][4][5]
6. 6Then check the wastegate, the turbo control flap, the intercooler and the air filter, and check whether there are control unit software updates.^[1][2]

Faults in which this code appears

• Medium severityOccasionalFrequency: Occasional2.3 MultiJetEGR valve and throttle body clogged by carbon deposits and moistureThe 2.3's EGR and intake throttle body clog up with carbon, soot and, in the throttle body, moisture: the engine goes into limp mode, loses power and shows an EGR warning. On the dual-EGR Euro 6, the low-pressure cooler is added to the list. Almost all of this comes from forums and commercial websites.