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Home / DTC / P0299 — Turbocharger/Supercharger A Underboost Condition

P0299 — Turbocharger/Supercharger A Underboost Condition

Detailed page for trouble code P0299.

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Code

P0299

Generic P — Powertrain

Turbocharger/Supercharger A Underboost Condition

Brand: Generic
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Boost leak in intake or intercooler piping
  • Wastegate stuck open or wastegate actuator fault
  • Boost control solenoid (N75/boost control valve) or its wiring faulty
  • Turbocharger mechanical problems (worn shaft, damaged compressor, turbine damage)
  • Vacuum/pressure supply to actuator leaking or disconnected
  • Restricted intake or exhaust (clogged air filter, catalytic converter)

Symptoms

  • Reduced engine power and poor acceleration
  • Longer than normal turbo spool time (delayed boost)
  • Engine may run lean or show hesitation under load
  • Black smoke from exhaust (if rich compensation occurs)
  • Illuminated check engine light (CEL) with stored P0299
  • Unusual turbo noise (whine, grinding) if turbo damaged

What to check

  • Verify DTC with scan tool, check freeze frame and readiness status
  • Compare commanded boost vs actual boost (MAP or boost sensor) across RPM/load
  • Inspect all intercooler and intake hoses, clamps, and connections for leaks or damage
  • Check wastegate actuator movement and linkage for free travel and correct operation
  • Test boost control solenoid function and wiring for continuity, short, and proper supply/ground
  • Perform a smoke test or pressure test of intake system to find leaks

Signal parameters

  • Commanded boost pressure (kPa or psi) vs measured boost (MAP sensor) under defined RPM/load
  • Boost control solenoid duty cycle (%) or PWM command
  • Wastegate actuator position or applied pressure/vacuum (mmHg/kPa)
  • Turbo speed or turbine RPM (if available)
  • MAF sensor airflow (g/s) and MAP sensor absolute pressure (kPa)
  • Intake manifold absolute pressure under boost and at idle

Diagnostic algorithm

  1. Retrieve freeze frame and live data with a scan tool. Note commanded boost, actual boost, MAF, MAP, throttle position, and fuel trims at time of fault.
  2. Visually inspect intake hoses, intercooler, clamps, and couplings. Tighten clamps and replace damaged hoses. Re-test for the code.
  3. Perform a smoke or pressure test on intake/intercooler system to locate leaks. Repair any leaks found and clear codes.
  4. With engine off, inspect wastegate actuator and linkage for free movement. Manually actuate where possible to confirm operation. Replace or repair if stuck or binding.
  5. Test boost control solenoid electrically (apply bench power where safe) and check vacuum/pressure lines for blockages. Replace solenoid or lines if faulty.
  6. Check turbocharger for shaft play (axial/radial) and inspect compressor/turbine wheels for damage. If excessive play or damage present, consider turbo rebuild/replacement.
  7. Confirm MAP/boost sensor and MAF sensor operation by comparing to known-good values or replacing with a known-good sensor if readings are implausible.
  8. Check for exhaust restrictions (collapsed catalytic converter or clogged DPF) causing excessive backpressure and reduced boost. Repair as needed.
  9. After repairs, clear codes and perform road test under the same conditions to confirm commanded vs actual boost and that P0299 does not return.
  10. If code persists after mechanical checks, inspect ECM software updates, consult manufacturer technical service bulletins, or seek advanced diagnostics for intermittent electrical issues.

Likely causes

  • Leaking or disconnected intake/intercooler hose or clamp
  • Faulty or stuck wastegate/wastegate actuator
  • Failed boost control solenoid or solenoid plumbing/valve
  • Damaged turbocharger (internal boost loss)
  • Faulty boost/MAP sensor or sensor reference/vacuum line

Fault status

⚠️ Status
P0299 stored when measured boost pressure is significantly lower than commanded for current operating conditions (turbocharger/supercharger A underboost).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1 to 4 hours

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Code

P0299

LAND ROVER P — Powertrain

Turbo / supercharger with supercharging

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Boost leak in intake or intercooler piping
  • Wastegate stuck open or wastegate actuator fault
  • Boost control solenoid (N75/boost control valve) or its wiring faulty
  • Turbocharger mechanical problems (worn shaft, damaged compressor, turbine damage)
  • Vacuum/pressure supply to actuator leaking or disconnected
  • Restricted intake or exhaust (clogged air filter, catalytic converter)

Symptoms

  • Reduced engine power and poor acceleration
  • Longer than normal turbo spool time (delayed boost)
  • Engine may run lean or show hesitation under load
  • Black smoke from exhaust (if rich compensation occurs)
  • Illuminated check engine light (CEL) with stored P0299
  • Unusual turbo noise (whine, grinding) if turbo damaged

What to check

  • Verify DTC with scan tool, check freeze frame and readiness status
  • Compare commanded boost vs actual boost (MAP or boost sensor) across RPM/load
  • Inspect all intercooler and intake hoses, clamps, and connections for leaks or damage
  • Check wastegate actuator movement and linkage for free travel and correct operation
  • Test boost control solenoid function and wiring for continuity, short, and proper supply/ground
  • Perform a smoke test or pressure test of intake system to find leaks

Signal parameters

  • Commanded boost pressure (kPa or psi) vs measured boost (MAP sensor) under defined RPM/load
  • Boost control solenoid duty cycle (%) or PWM command
  • Wastegate actuator position or applied pressure/vacuum (mmHg/kPa)
  • Turbo speed or turbine RPM (if available)
  • MAF sensor airflow (g/s) and MAP sensor absolute pressure (kPa)
  • Intake manifold absolute pressure under boost and at idle

Diagnostic algorithm

  1. Retrieve freeze frame and live data with a scan tool. Note commanded boost, actual boost, MAF, MAP, throttle position, and fuel trims at time of fault.
  2. Visually inspect intake hoses, intercooler, clamps, and couplings. Tighten clamps and replace damaged hoses. Re-test for the code.
  3. Perform a smoke or pressure test on intake/intercooler system to locate leaks. Repair any leaks found and clear codes.
  4. With engine off, inspect wastegate actuator and linkage for free movement. Manually actuate where possible to confirm operation. Replace or repair if stuck or binding.
  5. Test boost control solenoid electrically (apply bench power where safe) and check vacuum/pressure lines for blockages. Replace solenoid or lines if faulty.
  6. Check turbocharger for shaft play (axial/radial) and inspect compressor/turbine wheels for damage. If excessive play or damage present, consider turbo rebuild/replacement.
  7. Confirm MAP/boost sensor and MAF sensor operation by comparing to known-good values or replacing with a known-good sensor if readings are implausible.
  8. Check for exhaust restrictions (collapsed catalytic converter or clogged DPF) causing excessive backpressure and reduced boost. Repair as needed.
  9. After repairs, clear codes and perform road test under the same conditions to confirm commanded vs actual boost and that P0299 does not return.
  10. If code persists after mechanical checks, inspect ECM software updates, consult manufacturer technical service bulletins, or seek advanced diagnostics for intermittent electrical issues.

Likely causes

  • Leaking or disconnected intake/intercooler hose or clamp
  • Faulty or stuck wastegate/wastegate actuator
  • Failed boost control solenoid or solenoid plumbing/valve
  • Damaged turbocharger (internal boost loss)
  • Faulty boost/MAP sensor or sensor reference/vacuum line

Fault status

⚠️ Status
P0299 stored when measured boost pressure is significantly lower than commanded for current operating conditions (turbocharger/supercharger A underboost).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1 to 4 hours

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P0298 P0234 P2263 P0101 P0102 P0103
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