P0167
O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)
When a vehicle powertrain module registers the fault code P0167, it points directly to an internal system malfunction identified as "O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
A P0167 fault code points directly to a problem with o2 sensor heater circuit malfunction (bank 2 sensor 3) that the ECM has confirmed over multiple drive cycles. In practice, this fault causes check engine light on startup, delayed closed-loop fuel control. Low severity — the car drives normally, but the fault should be diagnosed and resolved within the next few weeks.
Symptoms
Check engine light on startup, delayed closed-loop fuel control
Common Causes
- Burned out internal O2 sensor heater
- Blown fuse for O2 sensor heaters
- Open circuit in wiring
- Poor ground
How to Fix
- 1 Replace Bank 2 Sensor 3
- 2 Check and replace related fuses
- 3 Test continuity and repair open wires
- 4 Clean ground terminals
Technical Explanation
The ECM detects code P0167 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The module measures the voltage return on the 5V reference circuit, comparing it to the expected signal envelope at current engine load and RPM. A deviation greater than the calibrated threshold — typically ±10% outside the normal operating window — flags the fault. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
Code P0167 has minimal impact on immediate driving safety. However, the underlying burned out internal o2 sensor heater issue will cause this vehicle to fail an emissions inspection and may gradually affect fuel economy if left unrepaired.
Mechanic's Pro Tip
Before replacing any component on P0167, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Fuse: $10; O2 sensor: $150 - $300