P0155: P0155: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
Standard SAE J1979 OBD-II diagnostic trouble code definitions, freeze-frame sensor telemetry, electrical multimeter benchmarks, and step-by-step DIY repair flowcharts.
1. Symptoms & Warning Signs
When fault code P0155 is triggered by the Engine Control Module (ECM), drivers frequently experience the following symptoms:
2. Most Likely Causes
Root cause statistical probability compiled from NHTSA ODI complaint telemetry, ASE Master Technician field records, and OEM Factory Service Manual diagnostic trees for P0155:
3. Step-by-Step DIY Repair Instructions
Inspect the O2 HTR fuse in the engine fuse box with a test light or multimeter.
Unplug the sensor connector and measure resistance between the two heater pins. An open circuit (infinite ohms / OL) confirms a dead internal heater.
Remove faulty sensor and install a new OEM oxygen sensor with built-in heater.
Clear DTCs and allow engine to cool down, then restart to confirm P0155 does not return.
Equipment for Diagnosing Universal Automotive (P0155)
Universal Automotive OEM Replacement Sensor
Direct-fit replacement assembly engineered to OEM tolerances for Universal Automotive.
AstroAI Auto-Ranging Digital Multimeter
Essential for testing 0.1V–5.0V sensor reference signals, ground continuity (<0.20Ω), and harness resistance.
BlueDriver Bluetooth Pro OBDII Scan Tool
Reads and clears enhanced codes (ABS, Airbag, Transmission, Engine) & live freeze-frame telemetry on phone.
Fix P0155 on 25 Specific Automakers
Manufacturer-specific wiring harnesses, sensor pinouts, and Technical Service Bulletins for P0155:
4. P0155 Frequently Asked Questions
Why do O2 sensors have internal heaters?
O2 sensors require temperatures above 600°F (315°C) to generate accurate voltage signals. The electric heater warms the sensor in under 30 seconds rather than waiting for exhaust heat alone.