Solving P0135 in Your 2024 Subaru Impreza
Your 2024 Subaru Impreza triggered P0135—O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 1. The upstream oxygen sensor's heater on the driver's side has failed.
Without the heater, your Impreza runs inefficiently until natural engine heat warms the sensor—wasting fuel each start.
Symptoms
- Check engine light on
- 9-17% reduced fuel economy
- Rough cold-start idle
- Hesitation during acceleration
- Extended warm-up period
- Failed emissions test
Common Causes
Failed Heater Element (62% Likelihood)
Your 2024 Impreza's 2.0L boxer engine creates thermal stress. Even in new vehicles, early failures occur from manufacturing defects.
Wiring Damage (24% Likelihood)
Sensor wiring in boxer engine layout endures heat and vibration near exhaust.
Blown Fuse (9% Likelihood)
Check fuse first—easiest fix.
ECM Software Issue (5% Likelihood)
Rare ECM glitches trigger false codes.
Diagnosis
- Verify P0135
- Check fuse
- Inspect wiring (Bank 1 = driver's side)
- Test heater resistance (4-12 ohms)
- Check voltage
- Monitor live data
Repair Costs
Subaru Dealership
Your 2024 Impreza is under warranty. Repairs should be free.
Out of warranty: $258-$385
Independent Shop
Cost: $178-$310
DIY
Cost: $73-$140
Time: 38-55 minutes
Parts
- OEM Subaru: $115-$160
- Denso: $73-$118
- Bosch: $78-$128
Prevention
- Use Top Tier fuel
- Address oil consumption
- Fix exhaust leaks
- Avoid unapproved additives
- Take longer drives
Driving with P0135
Safe short-term, but fuel economy drops 9-17%. Schedule repairs within 2 weeks to prevent catalytic converter damage ($1,000-$2,300).
When to Get Help
- Under warranty (free service)
- Uncomfortable with boxer engine work
- Code returns after replacement
- Multiple codes
2024 Impreza Notes
The Impreza's boxer engine layout places sensors uniquely. Check dealer for TSBs applicable to your VIN.