Honda Accord · Diagnostic Trouble Code
P0141 — O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
What it means, how urgent it is, the most likely causes, and the exact order to diagnose it — with the repair guides that fix it.
What P0141 means
Like all modern O2 sensors, the downstream sensor has an internal heater so it reaches operating temperature quickly after a cold start. The PCM watches the heater circuit's electrical signature; an open, short, or out-of-range current draw sets P0141.
Sensor 2 sits after the catalytic converter and its job is monitoring converter efficiency, not fuel control — so a heater failure here affects emissions diagnostics, not how the engine runs. The sensor usually still reads correctly once the exhaust is hot.
⚠️ How urgent is it?
Fix it before inspection. Diagnosis is the same drill as any heater code: fuse, heater resistance, power and ground at the connector. The downstream sensor is usually the easiest O2 sensor on the vehicle to reach.
Most likely causes
- A burned-out heater element in the downstream oxygen sensor — the most common cause.
- Wiring damage in the heater circuit: blown fuse, chafed wires near the exhaust, corroded connector.
- Exhaust heat cooking the sensor's wiring over time.
- Rarely, a PCM heater-driver fault.
How to diagnose it — in order
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1
Check the O2 heater fuse first — quick and cheap.
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2
Unplug the sensor and measure heater resistance across the two heater wires (usually the same-color pair). Open circuit means a dead heater element.
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3
Verify battery voltage reaches the heater power wire with the key on.
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4
Inspect the wiring run for melted insulation or chafing where it passes near the exhaust.
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5
Confirm the sensor signal itself is still alive — a good downstream sensor at operating temperature should show a fairly steady mid-range voltage, not flatlined.
Reading the code is step zero
A basic OBD2 scanner plugs into the port under your dash and tells you exactly which codes are stored — plus freeze-frame data showing what the engine was doing when the code set.
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Repair guides that fix P0141
General diagnostic information, not a factory service procedure. If you're unsure, have a qualified technician confirm the diagnosis before buying parts.