Turbo and forced inductionGeneric OBD-II codeUrgency: Garage soon

P0299 on Fiat: causes and affected engines

P0299 means: turbocharger or supercharger "A": insufficient boost pressure (underboost).^[1][2] Fiat has 9 documented faults that can trigger it, across 7 engines, including 1.4 T-Jet, 1.3 Multijet, 1.9 JTD/Multijet and 2.4 JTD and 0.9 TwinAir and 1.0/1.3 FireFly. Only a diagnosis can confirm the cause on your car.

Documented faults

that can trigger it

Engines

used by Fiat, with at least one of them

Fiat models

with at least one of these faults

Urgency

Garage soon

Reviewed on 9 October 20262 sources How we work

Documented faults in Fiat engines that can trigger P0299

Grouped by engine or model, from most to least important. These are faults with the turbo and with the EGR valve: not all of them will necessarily set the code, and only a diagnosis confirms the cause on your car.

1.4 T-Jet

In 500L, 500X, Bravo, Doblò II, Punto III and Tipo

- High severityFrequency: CommonTurboPremature turbocharger failure or wearOn the Fiat 500X, Fiat Tipo, Jeep Renegade and Jeep Compass there are recurring reports of turbocharger failure, sometimes at very low mileage (from 15,000 km); the manufacturer has offered occasional goodwill discounts, but there is no official campaign.Repair: €1,100–€2,300Appears at around 15,000 km

1.3 Multijet

In 500, 500L, 500X, Doblò II, Panda III, Punto III and 2 more models

1.9 JTD/Multijet and 2.4 JTD

In Bravo, Croma, Doblò I, Punto II, Punto III and Stilo

0.9 TwinAir and 1.0/1.3 FireFly

In 500, Panda III and Punto III

- High severityFrequency: OccasionalTurboEarly turbocharger failure (0.9 TwinAir)The 0.9 TwinAir's turbo can fail, in some cases at low mileage: there is one documented case replaced under warranty at 13,000 km in the Fiat 500 and another, a turbo hose, at 51,000 km in the Fiat Panda III. A specialist German source describes it as an infrequent problem.

1.6 and 2.0 MultiJet II

In 500L, 500X, Bravo, Doblò II, Freemont and Tipo

- Medium severityFrequency: CommonEmissions controlEGR valve blocked by soot in urban useYes: the EGR valve builds up soot with urban use and short journeys, which causes loss of power and turns on the engine fault warning light. It is one of the most frequently cited faults of this engine in both the Jeep Renegade and the Fiat Doblò.Repair (garage): €200–€500

2.3 MultiJet

In Ducato III

- Medium severityFrequency: OccasionalEmissions controlEGR 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.

2.4 JTD / JTDm Multijet

In Croma

- Medium severityFrequency: OccasionalEmissions controlClogged or faulty EGR valve on the 2.4 JTD and JTDmThe EGR valve is the most-cited fault in the testimonies for the 200 hp 2.4 JTD of the Alfa 159: 24 mentions in 63, plus 8 in 36 for the 210 hp and 12 in 64 for the 156. It gets dirty or fails; RACE puts the cost of replacing an EGR between €130 and €800 on cars in general (not a price specific to this engine).Repair (garage): €130–€800

Common causes of P0299 on any make

From most to least likely, according to the sources.

1Air leaks in the boost hoses or the intercooler, from a split hose or a loose clamp: this is the most common cause.^[1][2]
2Faulty wastegate or its actuator, or a seized turbo, which do not regulate the pressure properly.^[1][2]
3Worn or faulty turbo.^[1][2]
4Blocked intercooler or intake.^[2]

What to check first

The first diagnostic steps, from the most likely and cheapest to check to the most expensive.

1First check the boost hoses and the intercooler: cracks, oil at the joints and loose clamps. This is the most common cause and the cheapest to repair.^[1][2]
2With a diagnostic tool, compare the boost pressure requested by the control unit with the pressure measured by the sensor while you accelerate.^[2]
3Check that the wastegate actuator (or variable geometry actuator) moves and that its rod travels the full stroke, and check the solenoid valve that controls it.^[1][2]

Full guide to P0299: symptoms, diagnosis and whether you can drive

Frequently asked questions

Which Fiat engines have faults that can trigger P0299?

1.4 T-Jet (1 fault), 1.3 Multijet (2 faults), 1.9 JTD/Multijet and 2.4 JTD (2 faults), 0.9 TwinAir and 1.0/1.3 FireFly (1 fault), 1.6 and 2.0 MultiJet II (1 fault) and 2.3 MultiJet (1 fault). Each fault has its own page with the affected years and versions, the symptoms and the repair cost.

What does code P0299 mean on a Fiat?

Turbocharger or supercharger "A": insufficient boost pressure (underboost). The engine control unit has detected that the turbo is not delivering the expected boost pressure: the actual pressure falls below what the engine management requests. That is why, to diagnose it, the requested pressure is compared with the measured pressure using a diagnostic tool. It is a generic OBD-II code: it means the same on a Fiat as on any other make.^[1][2]

Can I keep driving with P0299?

Garage soon. You can normally get to the garage by driving gently, often in degraded mode, but you should not carry on using the car as normal: the fault can end up causing more serious engine damage.^[1][2]

Sources

Every fact on this page links to its source. If you find an error, let us know.

Qué significa el código P0299Autodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
P0299: Turbocharger/Supercharger A Underboost ConditionCarista · Technical documentation · consulted 2 October 2026