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

P0299 Turbocharger/Supercharger A Underboost Condition

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0299 means actual boost stays below target for a period although the control already demands more. Thresholds: GM petrol 30–55 kPa below target with the warning light in the first trip; GM diesels 10–50 kPa, two trips; Ford EcoBoost more than 4 psi (about 28 kPa) for 5 s with the wastegate already commanded fully closed; Ford diesels 30–40 kPa for 10–15 s, with a further underboost code P2263. Typical causes from manufacturer bulletins: a charge air leak, a wastegate that lost its preload or whose rod came off, a leaking bypass valve, sticking turbo vanes on diesels, and ice in the charge air cooler in winter. A faulty boost sensor can also fake underboost. Many engines then limit power.

Likely causes

Leak in the charge air path (hose off or torn, cooler leaking, clamps)
Wastegate faulty (rod off, preload lost, vacuum or solenoid, diaphragm)
Turbo vanes sticking or turbo worn (diesel)
Bypass valve leaking (torn diaphragm) or its control
Ice in the charge air cooler, boost sensor or connector, or software

Symptoms

  • Loss of power, sluggish acceleration
  • Limp mode, power limited
  • Check engine light on
  • Whistling or hissing from the charge air path under load

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–2,500
Time0.5–6 h

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

What to check first

  1. Pressure-test the intake for boost leaks
  2. Inspect hoses and intercooler
  3. Check actuator movement

Parts involved

turbochargerwastegatecharge air hosesboost pressure sensor a

Related codes

P0234P2263P0236P0238P0033P259E

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.