What does code P1166 mean on Honda vehicles?
The ECU detects an electrical malfunction in the heater circuit of the primary oxygen sensor.
OBD-II Code Honda
P1166 — Honda — Primary HO2S (No. 1) Heater System Electrical
The ECU detects an electrical malfunction in the heater circuit of the primary oxygen sensor.
Common symptoms
- Check engine light illuminated
Possible causes
- Faulty heater circuit
- wiring damage
- blown fuse
Initial recommendation
Inspect O2 sensor heater circuit and repair wiring or replace sensor.
Safety notice
This information is for guidance only. Brand-specific codes may vary by model, year, engine, transmission and vehicle configuration. It does not replace a physical inspection or diagnosis by a qualified mechanic. If the vehicle is unsafe to operate, avoid driving it and seek professional inspection.
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