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2020 Eclipse Cross 1.5T Turbo Lag and P0299 Code

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Mike T. · rep 0 · May 22, 5:31 AM · 1 replies · solved · Question

Vehicle: 2020 Mitsubishi Eclipse Cross SEL

Hey guys,

I'm having some trouble with my 2020 Mitsubishi Eclipse Cross SEL, which has the 1.5L turbo engine. Lately, I've noticed a significant increase in turbo lag, and the car just doesn't feel as responsive as it used to be. It's especially noticeable when trying to accelerate quickly or merge onto the highway.

To make matters worse, the check engine light came on yesterday, and when I scanned it, I got a P0299 code, which points to 'Turbocharger/Supercharger Underboost'. I've checked some of the visible hoses for cracks, but I haven't found anything obvious. The car still drives, but it feels sluggish.

Has anyone dealt with this specific issue on their Eclipse Cross or other Mitsubishi turbo models? What should I be looking for, or what are the common culprits for this code and symptom combination?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:31 AM

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ClearTheCode admin answer:

The P0299 code (Turbocharger/Supercharger Underboost) on your 2020 Mitsubishi Eclipse Cross 1.5T is a clear indicator that the engine's boost pressure is lower than what the Powertrain Control Module (PCM) expects. This directly explains the increased turbo lag and sluggish performance you're experiencing.

Common Causes for P0299:

  1. Boost Leaks: This is the most frequent cause. Check all intercooler hoses, clamps, and connections for cracks, loose fittings, or punctures. A small leak can significantly reduce boost.
  2. Wastegate Actuator/Valve Issues: The wastegate controls exhaust flow to the turbo. If it's stuck open, partially open, or its actuator is faulty, boost pressure won't build correctly.
  3. Diverter Valve/Bypass Valve Failure: This valve releases excess boost pressure when you lift off the throttle. If it's stuck open or leaking, boost will escape.
  4. Faulty Turbocharger: While less common, the turbocharger itself could be failing (e.g., worn bearings, damaged compressor/turbine wheels).
  5. MAP/Boost Sensor Malfunction: A faulty Manifold Absolute Pressure (MAP) sensor or boost sensor could be sending incorrect readings to the PCM, leading it to believe there's an underboost condition when there isn't, or vice-versa.
  6. Clogged Catalytic Converter/Exhaust Restriction: Although less direct, a severely restricted exhaust can impede turbo operation.

When to See a Shop: Since you have a check engine light and a specific code, it's best to have a professional diagnosis. While you can visually inspect hoses, a shop has specialized tools to perform a smoke test for boost leaks and can properly test the wastegate, diverter valve, and sensors.

Recommended Steps:

  1. Professional Diagnostic Scan: A shop will use an advanced scanner to check for other related codes and monitor live data from boost sensors.
  2. Boost Leak Test: This involves pressurizing the intake system to pinpoint any leaks.
  3. Wastegate/Diverter Valve Inspection: Check for proper operation and vacuum line integrity.
  4. Turbocharger Inspection: Assess the turbo for shaft play or damage.

Addressing this promptly will restore your vehicle's performance and prevent potential long-term engine issues.

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