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Discussion Starter · #1 ·
Alright hoping to get some feedback here. I bought my truck bone stock and kept it that way till a few weeks ago when towing my 20' race trailer the DPF started giving me issues @ 148K miles. The next week I installed the 4" exhaust and the EFI by millken diesel. i got the blocker plates for the EGR but have yet to install because after doing some research i want to do the Y-bridge upgrade with the LB7 up-pipe to completely remove the EGR. I was towing today and it was doing great ( I keep it on the stock tune with deletes while towing) but about 15 miles into the trip I noticed a loss of boost and it would seemed like the turbo vane position would cycle about every 5 seconds and would blow a small cloud of black smoke and then lose power to the point of it going into limp mode and throwing the p0299 under-boost code. i got off at the next exit of course and limped it the 45 min to the track and cleared the code and it ran phenomenal all the way home. I'm looking for anything help in beginning to troubleshoot. Could not blocking the EGR cause this? Thanks in advance for any help here cause I'm stumped.

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DTC P0299

Diagnostic Instructions

  • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure
  • Review Strategy Based Diagnosis for an overview of the diagnostic approach
  • Diagnostic Procedure Instructions provide an overview of each diagnostic category
DTC Descriptor

DTC P0299: Turbocharger Engine Underboost

Circuit/System Description

The manifold absolute pressure (MAP) sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by turbocharger output, engine speed, accelerator pedal input, ambient air temperature, and barometric pressure (BARO). A diaphragm within the MAP pressure sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates these changes into electrical resistance. The engine control module (ECM) supplies a regulated 5 volts on the 5-volt reference circuit and a ground on a low reference circuit. The MAP sensor provides a signal voltage to the ECM, relative to intake manifold pressures, on the MAP sensor signal circuit. The ECM converts the signal voltage input to a pressure value. Under normal operation, the lowest pressure that can exist in the intake manifold is equal to the BARO. This occurs when the vehicle is operated at idle or when the ignition is ON while the engine is OFF. The highest manifold pressures occur when the turbocharger output is high. Manifold pressure can range from 58 kPa (8 psi) when pressures are low to more than 295 kPa (42.7 psi) when pressures are high, depending on the BARO. The MAP pressure sensor has a range of 43-365 kPa (6-53 psi). The ECM monitors the MAP sensor by comparing a calculated predicted value at a predetermined engine load and speed, to the actual sensor input.

Conditions for Running the DTC

  • DTCs P2564 or P2565 are not set.
  • The engine speed is between 800-3,000 RPM.
  • DTC P0299 runs continuously when the above conditions are met.
Conditions for Setting the DTC

The measured MAP pressure is more than 39 kPa below the expected range for 10 seconds.

Action Taken When the DTC Sets

  • DTC P0299 is a Type A DTC.
  • A message center or an indicator may display reduced engine power.
  • The ECM commands reduced engine power.
  • Diesel particulate filter (DPF) regeneration is inhibited.
Conditions for Clearing the DTC

DTC P0299 is a Type A DTC.

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Verify that DTCs P003A, P0047, P0048, P046C, P0402, P0403, P0698, P0699, P2563, P2564 or P2565 are not set.

    • If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis

  1. Engine running, command the TC Vane Pos. Ctrl. Solenoid ON, while performing a snapshot of the induction data list. Perform the following actions during the snapshot: Refer to Scan Tool Snapshot Procedure
2.1. Slowly increase the engine speed to 1,700 RPM for 5 seconds and then return the engine speed to idle. 2.2. Plot the snapshot and verify that the MAP sensor parameter increases smoothly and follows the Engine Speed parameter as the engine speed is increased, and then returned to idle.
  • If the MAP parameter plot slope is not a straight line with even the RPM change, replace the MAP sensor.

  1. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing

Important: Perform the Repair Verification after completing the Circuit/System Testing.

  1. Verify the integrity of the air induction system, the turbocharger ducts and hoses by inspecting for the following conditions:

    • Any damaged components
    • Any loose or improperly installed components
    • A wet or restricted air filter
    • Any exhaust leaks before the turbocharger
    • Any exhaust restrictions after the turbocharger
    • Any snow or ice build-up at the air cleaner and MAF sensor
    • Any water, snow, ice build-up, restrictions or coking at the MAP sensor

  1. Test the charge air system for air leaks. Refer to Charge Air Cooler Diagnosis for Full System Air Leak Test
  2. Test the turbocharger oil supply feed. Refer to Turbocharger Lack of Oil Supply
  3. Inspect the turbocharger oil supply tube for restrictions.

    • If a restriction is found, clean or replace the oil supply tube as necessary.

  1. Inspect the turbocharger for debris, worn impeller and turbine blades, or damage Refer to Turbocharger Cleaning and Inspection

    • If worn or damaged turbocharger blades or vanes are found, replace the turbocharger assembly.

  1. If the induction system, charger air cooler system, the turbocharger, and the turbocharger oil supply test normal, replace the MAP sensor.

Repair Verification

  1. Install any components or connectors that have been removed or replaced during diagnosis.
  2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
  3. Clear the DTCs.
  4. Turn OFF the ignition for 60 seconds.
  5. Duplicate the Conditions for Running the DTC and use the freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure
  6. If any service has been performed on the turbocharger or on the turbocharger components, a turbocharger relearn must be performed. Failure to perform the turbocharger learn procedure may cause this DTC to set. Refer to Turbocharger Learn
  7. Perform the Diesel Particulate Filter (DPF) Service Regeneration
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