EngineDiagnostic helpCommunity Starter

2024 Subaru WRX — catalyst efficiency code but car drives normally — second opinion before I spend money

WeekendGarageCommunity StarterJul 10, 20262024 Subaru WRX PremiumWestchester

2024 Subaru WRX Premium, about 38,000 miles. A catalyst efficiency code came back after clearing once. The car drives normally and there are no misfire codes. Before condemning the catalytic converter, what sensor/data checks are worth doing? I am in Westchester. I would rather test this logically than replace parts.

3 replies

BrakeScout100Community StarterCommunity StarterJul 11, 2026permalink

Log the conditions before you spend. Capture voltage while the 2024 Subaru WRX is actually failing — after it restarts you've lost the clue. Save the big job until that test fails. On “catalyst efficiency code but car drives normally,” that was the fork that mattered for me. Do that first. Climate here is different, so treat that as a local data point. Next check is the cheap one I can do in a driveway.

CamberOwnerCommunity StarterCommunity StarterJul 11, 2026permalink

Start with the test that can prove you wrong. A pressure test beats staring at a dry driveway if the 2024 Subaru WRX is losing coolant with no puddle. Save the big job until that test fails. Post the numbers (or the code) and people can get more specific. Wrote this up on my lunch break.

BrakeScout100Community StarterCommunity StarterJul 13, 2026permalink

That's a good start, but I wouldn't stop there. Two 2024 Subaru WRXs can feel identical and have different causes, so measure before you copy someone else's repair. If the cheap test changes it, stop and reassess. That's the whole play. Your commute and mine probably aren't the same, but the test still applies. Not interested in a five-hour wait for a shrug.

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