Toyota P1155: A/F Sensor Heater (B2S1) — Fix
On Toyota vehicles, P1155 means a fault in the air/fuel-ratio (A/F) sensor heater circuit for bank 2, sensor 1 — the same fault as P1135 on the other bank.
- Applies to
- Toyota vehicles
- Est. repair cost
- $40 – $400
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include a failed A/F sensor heater, a blown fuse, or wiring/connector faults on bank 2. P1xxx codes are manufacturer-specific — P1155 is defined by Toyota (not part of the generic SAE J2012 set), so this definition applies to Toyota vehicles. Model years can vary, so confirm against the Toyota service manual. Fix the fault, then clear the code with a scan tool.
Symptoms
- Check engine light on
- Slower closed-loop when cold
- Worse cold-start economy
How to fix it
- 1
Check fuse and wiring
1. Confirm the A/F heater fuse. 2. Inspect the bank 2 sensor connector.
- 2
Replace the A/F sensor
1. Test the heater circuit. 2. Replace the bank 2 A/F sensor if open, then clear the code.
Frequently asked questions
Where is bank 2 on my Toyota?
On a V6, bank 2 is the cylinder bank without cylinder 1. P1155 is its upstream A/F sensor heater fault.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.