MechanicDB
Home / Diagnostic Decoder / Powertrain System / Code P1155
System: Powertrain (P-Code) Coverage: OEM Specific (Toyota) Fault Family: o2_heater_circuit

Code P1155: Air/Fuel Sensor Heater Circuit Bank 1 Sensor 2

Diagnostic & Technical Explanation
Code P1155 (Air/Fuel Sensor Heater Circuit Bank 1 Sensor 2) sets when the ECM detects an open, shorted, or out-of-spec resistance in the internal heater element of an oxygen sensor, or the heater fails to bring the sensor to operating temperature within the expected time. This is almost always a degraded heater element inside the O2 sensor itself, though a blown fuse, relay, or chafed heater wiring can also be responsible.

Probability-Ranked Repair Procedures (3 Ranked Fixes)

Rank #1

Test O2 sensor heater circuit fuse and relay

Easy DIY
Parts Estimate: $5.0–$25.0 USD Labor Estimate: 0.4 Shop Hours
  1. 1. Locate the O2 heater fuse and relay in the underhood fuse box
  2. 2. Inspect and test with a multimeter for continuity and proper switching
  3. 3. Replace any blown fuse or failed relay
  4. 4. Clear codes and verify heater current draw
Required Replacement Parts: 🔧 Automotive fuse assortment · 🔧 Relay (O2 heater circuit)
Rank #2

Replace oxygen sensor with failed heater

Moderate DIY
Parts Estimate: $50.0–$180.0 USD Labor Estimate: 0.6 Shop Hours
  1. 1. Identify the affected bank/sensor position from the code
  2. 2. Unplug the connector and remove the sensor with an O2 sensor socket
  3. 3. Apply anti-seize to threads (avoid the sensor tip) and install the new sensor
  4. 4. Reconnect and clear codes
Required Replacement Parts: 🔧 Oxygen sensor (heated, bank/position-specific) · 🔧 Anti-seize compound
Rank #3

Repair O2 heater circuit wiring

Professional Required
Parts Estimate: $10.0–$60.0 USD Labor Estimate: 1.2 Shop Hours
  1. 1. Measure heater element resistance at the connector against spec
  2. 2. Voltage-drop test the heater supply and ground legs
  3. 3. Repair chafed or corroded wiring near the exhaust manifold with high-temp splices
  4. 4. Confirm heater current draw matches spec
Required Replacement Parts: 🔧 High-temperature wiring repair kit

Need All 15,886 OBD-II Codes & 56,561 Fixes?

Download the complete commercial MechanicDB dataset instantly. Includes CSV, Apache Parquet tables, and a relational SQLite database with commercial application rights.

License Full Dataset · Instant Download ($49)