JCB P0299 – ECM: Turbo Low Boost

The Engine Control Module (ECM) has detected that the turbocharger is not producing the expected amount of boost pressure. The actual boost pressure measured by the sensor is significantly lower than the target pressure for a predetermined period, which suggests the turbo is not providing the expected level of boost pressure, often due to an air leak or an issue with the affected circuit.

• JS Series Crawler Excavators
• JS Series Wheeled Excavators
• Loadall Telehandlers
• Backhoe Loaders
• 540-140 Loadall

1. 1

   Read all fault codes with a diagnostic scan tool to identify related sensor (MAP, boost pressure) or wastegate control solenoid issues

2. 2

   Visually inspect the entire air intake system from the air filter to the intake manifold for cracked, split, or disconnected hoses, loose clamps, intercooler damage, or air filter blockages (most common cause)

3. 3

   Perform a boost pressure system leak test (smoke test) to visually identify any points where air escapes under low pressure

4. 4

   Inspect the turbocharger mechanically (engine off) for damaged compressor blades or excessive shaft play, and audibly (engine running) for high-pitched whining or whistling

5. 5

   Check wastegate operation to ensure the mechanical actuator rod moves freely and is not stuck open, or perform an electronic actuator test via scanner

6. 6

   Inspect the boost pressure, MAF, and MAP sensors for physical damage and ensure electrical connectors are clean and secure

7. 7

   Check engine oil level and quality, as inadequate lubrication can lead to turbocharger failure

1. 1

   Address related fault codes

   If other fault codes are present (especially related to sensors or the wastegate), diagnose and repair those issues first.

2. 2

   Repair boost leaks

   If leaks were found during the visual inspection or smoke test, replace the damaged hoses, clamps, or intercooler. Ensure all connections are secure.

3. 3

   Service air filter

   Clean or replace the air filter if it is dirty or clogged and restricting airflow to the turbo.

4. 4

   Test and replace sensors

   Test suspected faulty sensors (such as the boost pressure sensor) against manufacturer specifications. Replace if they fail.

5. 5

   Repair or replace wastegate components

   If the wastegate or its actuator is found to be faulty (e.g., stuck open, not holding pressure), repair or replace the component.

6. 6

   Replace turbocharger

   If the turbocharger shows signs of mechanical damage, excessive shaft play, or has seized, replace the turbocharger assembly.

7. 7

   Clear codes and test drive

   After any repair, clear the fault codes with a scan tool and perform a test drive under various load conditions to ensure the fault does not return.