Replace upstream or downstream O2 sensor (P0420/P0030 codes).
Reviewed by SubaruReview Editorial Team · Last reviewed 2026-05-10 · Editorial standards
How this repair stacks up against the other common Subaru engine jobs — useful when you're sequencing what to fix first.
| Repair | Cost range | Labor | Parts | DIY |
|---|---|---|---|---|
| Subaru Oxygen Sensor Replacement Cost (this page) | $200–$450 | 0.5–1.5 hrs | $80–$280 | 2/5 |
| Subaru Head Gasket Replacement Cost | $1,800–$3,200 | 12–16 hrs | $350–$650 | 4/5 |
| Subaru Timing Chain Replacement Cost (FB Engines) | $1,600–$2,800 | 8–12 hrs | $550–$850 | 5/5 |
| Subaru Water Pump Replacement Cost | $400–$1,150 | 2.5–6 hrs | $150–$350 | 4/5 |
| Subaru Timing Belt Replacement Cost | $750–$1,450 | 4–6 hrs | $350–$550 | 5/5 |
| Subaru Turbo Replacement Cost | $1,850–$3,800 | 5–8 hrs | $1200–$2600 | 4/5 |
This repair is part of our Subaru repair-cost database and connects back to the engine-family guides where we cover why each failure happens.
Sensors degrade naturally at 80-120k. Failures throw P0420 (cat efficiency) or P0030/P0050 (heater circuit) codes.
P0420 alone won't strand you, but unburned fuel can damage the catalytic converter ($1,500+ to replace).
Expect $200–$450 at most US shops, parts plus labor.
0.5–1.5 labor hours typically.
Yes — DIY difficulty 2/5.
P0420 alone won't strand you, but unburned fuel can damage the catalytic converter ($1,500+ to replace).
Cost, labor-hour, and parts-price ranges on this page are aggregated national-average estimates. Individual figures are not tied to a single primary source and should be treated as directional — request a written quote from a Subaru dealer or an independent Subaru specialist before booking work. See our editorial standards for how we build these ranges.
No primary source is currently cited for the specific figures on this page. Treat quantitative details as directional pending verification — see our Corrections Policy to help us update it.
Independent Subaru specialists usually come in $300–$1,000 below dealer pricing on the $200–$450 range shown above, without giving up OEM parts. See real quote breakdowns in the Subaru repair-costs hub.
The most common trigger is AC Compressor Failure, documented with symptoms, root cause, and a permanent-fix path. Fixing the underlying failure first is what stops you from paying for this job twice.
Bundling engine work at one visit almost always beats paying labor twice. Owners on this platform also price out Subaru Head Gasket Replacement Cost and Subaru Timing Chain Replacement Cost (FB Engines) at the same appointment.
Yes — we rate it 2/5. Follow the job-steps checklist above and the money-saving tips, and cross-check the reliability hub for related failures worth inspecting while you're in there.
It's tracked inside our Engine Guides cluster alongside every related failure and fix. Browse all topic hubs to see repair cost in the context of the underlying engine or drivetrain issue.
Dig into the Problems Database to plan your next maintenance sprint, or browse every model hub for buyer's guides, generation breakdowns, and known-issue lists.