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2017 ATS 2.0T Turbo Lag and P0299 Underboost Code

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Mike T. · rep 0 · May 25, 2:50 AM · 1 replies · solved · Question

Vehicle: 2017 Cadillac ATS 2.0T Luxury

Hey everyone, I've got a problem with my 2017 Cadillac ATS 2.0T Luxury. Lately, I've noticed a significant amount of turbo lag, and the car just doesn't feel as powerful as it used to. It's like the boost isn't kicking in properly.

Yesterday, the check engine light came on, and when I scanned it, I got a P0299 code, which points to an 'Engine Turbocharger/Supercharger Underboost' condition. I've heard this can be a common issue with these engines.

Has anyone else experienced this with their ATS? What were the common causes, and what kind of repair costs am I looking at? I'm hoping it's not a full turbo replacement.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:50 AM

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ClearTheCode admin answer:

The P0299 code on your 2017 Cadillac ATS 2.0T indicates that the engine's turbocharger or supercharger is not producing enough boost pressure. This is a common issue and can stem from several potential causes, not all of which require a full turbo replacement.

Here's a breakdown of common causes and steps:

  1. Vacuum Leaks: Check all vacuum lines, especially those connected to the wastegate actuator and diverter valve. A crack or loose hose can lead to boost loss.
  2. Diverter Valve Failure: The turbocharger's diverter valve (also known as a bypass valve) can fail, causing boost pressure to escape. This is a relatively common wear item.
  3. Wastegate Actuator Issues: The wastegate actuator controls the exhaust flow to the turbo. If it's stuck open, not fully closing, or has a faulty vacuum line, it won't build proper boost.
  4. Charge Air Cooler (Intercooler) Leaks: Leaks in the intercooler or its piping can cause a significant drop in boost pressure. Inspect for cracks or loose clamps.
  5. Turbocharger Failure: While less common for P0299 alone, a failing turbocharger (e.g., worn bearings, damaged compressor wheel) could be the root cause. However, this is usually accompanied by other symptoms like excessive smoke or whining noises.
  6. Exhaust Leaks: Leaks in the exhaust system before the turbo can reduce the exhaust energy available to spin the turbine, leading to underboost.

When to see a shop:

  • If you're not comfortable inspecting vacuum lines, hoses, or components yourself.
  • If a visual inspection doesn't reveal any obvious issues.
  • If the problem persists after checking simple items.
  • A professional diagnostic will involve pressure testing the intake system, checking wastegate operation with a scan tool, and potentially inspecting the turbocharger itself. Early diagnosis can prevent further damage or more costly repairs.
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