P0238 The turbocharger boost pressure sensor A is reporting a signal that is too high

Turbo boost sensor A circuit high

P0238 in short

P0238 means the turbo boost pressure sensor A is sending a signal that is too high. A damaged wire, a faulty sensor, a stuck waste gate or a blocked exhaust can cause it. Expect reduced power or limp mode. Get it checked soon, and stop if the engine knocks or loses power badly.

The boost sensor tells the computer how much pressure the turbo is making. If the reading is much higher than expected, it sets P0238 and may cut power to protect the engine.

Because a real overboost can damage the engine, the sensor and the boost control must both be checked.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Faulty boost sensor or damaged wiring and connector

    Common general cause
    Why it ranks here
    TroubleCodes.net lists wiring damage and a defective sensor first.
    What would change this
    Rises if reference voltage is outside 4.5 to 4.9 volts or the wiring is damaged. Falls if the sensor reads correctly.

  2. Stuck or failed waste gate or damaged vacuum lines

    Common general cause
    Why it ranks here
    TroubleCodes.net lists a failed waste gate and damaged vacuum lines, which would cause real overboost.
    What would change this
    Rises if the waste gate does not respond to commands. Falls if it moves normally.

  3. Clogged catalytic converter or muffler

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists exhaust restriction as a possible cause.
    What would change this
    Rises if exhaust backpressure is high. Falls if the exhaust flows freely.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Record codes and freeze-frame data, then look over the sensor wiring, connectors and vacuum lines.

    Low risk

  2. Check the sensor reference voltage and command the waste gate open and closed on a scan tool.

    Best left to a shopTool: scan tool, multimeter

    Warning:The turbo and exhaust are very hot, and testing can create high boost pressure. Let a shop do it.

Symptoms

  • Check engine light
  • Reduced power or limp mode Gets more serious: stop and have it checked.
  • Whistling or grinding from the turbo Gets more serious: stop and have it checked.

How to fix

  1. With the engine off and cool, look over the boost sensor connector and vacuum lines for damage.

On your vehicle

Cadillac

  • 2019 · XT4

    Supported by vehicle data

    GM preliminary information PIP5625 says P0238 can set after service work if the turbocharger air pressure sensor connector and the A/C refrigerant connector are swapped when the engine wiring harness is reassembled, on the 2019 XT4. Whether it is still current is not verified.

  • PIP5625Status unverified

    DTC P0238 after service when sensor connectors are swapped

    2019xt4 · issued · NHTSA 10154275

    GM preliminary information that P0238 can set after service work if the turbocharger air pressure sensor wiring connector and the A/C refrigerant wiring connector are accidentally swapped during engine wiring harness reassembly.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Jeep

  • 2015 · Renegade

    Supported by vehicle data

    Jeep bulletin 08-089-14 is a multi-module software update. One listed concern is P0238, turbo boost pressure sensor circuit high, with the MIL lighting sometimes at wide-open throttle on the 2.0L diesel Renegade. Whether it is still current is not verified.

  • 08-089-14Status unverified

    Flash: multiple ECU software enhancements

    2015renegade · issued · NHTSA 10139781

    Jeep bulletin for upgrading software in several modules. One listed concern is DTC P0238, turbo boost pressure sensor circuit high, with the MIL lighting sometimes during wide-open-throttle acceleration (2.0L diesel only).

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2003–2007 · F-250 Super Duty

    Supported by vehicle data

    Ford bulletin 06171 gives diagnostics and service tips for 6.0L turbocharger carbon deposits (lack of power, white or black smoke, surge) with P0238 among the codes listed, on 2003-2007 trucks. Whether it is still current is not verified.

  • 2003–2007 · Excursion

    Supported by vehicle data

    Ford bulletin 06171 gives diagnostics and service tips for 6.0L turbocharger carbon deposits (lack of power, white or black smoke, surge) with P0238 among the codes listed, including the Excursion. Whether it is still current is not verified.

  • 2003–2007 · E-350

    Supported by vehicle data

    Ford bulletin 06171 gives diagnostics and service tips for 6.0L turbocharger carbon deposits (lack of power, white or black smoke, surge) with P0238 among the codes listed, including the E-350. Whether it is still current is not verified.

  • 06171Status unverified

    6.0L turbocharger carbon deposit diagnostics, with P0238 among the codes

    2003–2007e-350, excursion, f-250-super-duty, f-350-super-duty, f-450-super-duty · NHTSA 10021232

    Ford bulletin with diagnostics and service tips for 6.0L turbocharger carbon deposits: lack of power, white or black smoke, surge, and codes including P0238, P0299, P0404, P2262 and P2263.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P0238 yet.

All Turbocharging, fuel pressure and EGR codes

P0238 questions

Is it safe to drive with P0238?

Only gently and for a short trip. Stop if power is lost or the turbo is noisy.

Sources and review

  1. P0238 trouble code summary — TroubleCodes.net
  2. PIP5625: DTC P0238 after service when sensor connectors are swapped — General Motors
  3. 08-089-14: Flash: multiple ECU software enhancements — Jeep
  4. 06171: 6.0L turbocharger carbon deposit diagnostics, with P0238 among the codes — Ford
  5. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles
Last reviewed
Written by
Saurabh K.
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