P0135 on the 2024 Honda Accord
The 2024 Honda Accord (11th generation) offers a 1.5L turbocharged four-cylinder (192 hp) and a 2.0L hybrid powertrain (204 hp combined). The P0135 code indicates a malfunction in the upstream O2 sensor heater circuit. On a 2024 model, this is most likely a manufacturing defect covered under Honda's warranty. The heater element warms the sensor to operating temperature quickly after startup for emissions compliance.
P0135 on the Accord's Two Powertrains
Both the 1.5T and the hybrid 2.0L use upstream O2 sensors with heater circuits. On the hybrid, the O2 sensor heater is particularly important because the engine cycles on and off during driving, requiring rapid sensor warmup each time the engine restarts. A heater malfunction on the hybrid means extended open-loop operation during each engine restart cycle.
Causes on a New Accord
- Factory sensor defect: An individual sensor with a manufacturing flaw in the heater element can fail within the first few thousand miles. This is the most likely cause on a nearly new 2024 Accord.
- Blown heater fuse: The underhood fuse box contains a dedicated O2 heater circuit fuse. While unlikely to blow without cause on a new car, a loose fuse or wiring issue at the fuse box can trigger P0135.
- Assembly wiring issue: The heater circuit wiring may have been improperly routed or pinched during assembly, creating an intermittent or steady open circuit.
- ECM driver issue: Rarely, the ECM's heater control transistor can have a manufacturing defect. This is diagnosed by exclusion after verifying the sensor, fuse, and wiring.
Symptoms
The check engine light is the primary symptom. On the 1.5T, cold-start performance may be slightly rough for the first minute. On the hybrid, the impact can be more noticeable since the engine cycles on and off: each restart takes longer to reach closed-loop fueling, reducing overall hybrid efficiency. Most drivers notice only the warning light during normal driving.
Warranty Coverage
Your 2024 Accord is fully covered under Honda's 3-year/36,000-mile basic warranty and the federal 8-year/80,000-mile emissions warranty. Schedule a visit at your Honda dealer for free diagnosis and repair.
Dealer Diagnosis
- Code verification with Honda Diagnostic System (HDS).
- O2 sensor heater fuse check.
- Heater circuit resistance measurement at the sensor connector.
- Heater circuit power supply verification.
- TSB check for the 2024 Accord platform.
Reference Costs
Under warranty: $0. Post-warranty reference: OEM Denso sensor: $90-$185. Dealer labor: $100-$180. Total: $190-$365. Honda dealer labor: $125-$175/hour.
After Service
The dealer will clear the code and verify heater operation. Drive normally for a few cycles to complete monitor resets. If the code returns, visit the dealer for further investigation under warranty.