Toyota Error Code P1155 – Air/Fuel Sensor Heater Circuit Bank 2 Sensor 1

🔍 What Does Toyota Error Code P1155 Mean?

P1155 – Air/Fuel Sensor Heater Circuit Bank 2 Sensor 1 occurs when the ECM detects an abnormal current or response from the A/F sensor heater circuit on bank 2. This sensor is critical for maintaining the correct air-fuel ratio, especially during cold starts.

📍 When and Why It Appears

• The heater circuit resistance is out of range
• The A/F sensor is faulty or slow to respond
• The wiring or connector to the sensor is open or shorted
• ECM detects improper voltage to the heater circuit

⚠️ Common Symptoms of P1155

• Check Engine Light ON
• Increased fuel consumption
• Hesitation or poor throttle response
• Failed emissions test

🔎 Possible Causes

• Failed A/F sensor (Bank 2 Sensor 1)
• Open or short in sensor wiring harness
• ECM malfunction (rare)
• Contaminated sensor tip (fuel additives, silicone)

🧰 How to Diagnose P1155

1. Scan for DTCs and review freeze frame data
2. Measure resistance across sensor heater terminals
3. Check voltage supply to heater circuit (should be around 12V)
4. Inspect wiring for breaks or corrosion
5. Compare A/F sensor response with Bank 1 (if available)

🔧 How to Fix Toyota Error Code P1155

1. Replace the A/F sensor on Bank 2 Sensor 1 with OEM spec
2. Repair damaged wiring or connector terminals
3. Check ECM and fuses for power/ground integrity
4. Clear codes and retest using live data for proper heater activation

💰 Estimated Repair Cost

• A/F Sensor Replacement: ₱2,500 – ₱6,000
• Wiring Repair: ₱800 – ₱2,000
• Diagnostics and Labor: ₱1,000 – ₱2,000

🧠 Expert Tips

• Only use Denso or OEM-specified A/F sensors
• After replacing, drive at various speeds to allow ECM relearning
• Don’t confuse O2 and A/F sensors — they function differently

❓ FAQ – Toyota P1155

Can I still drive with P1155?

Will cleaning the sensor fix the issue?

Is P1155 the same as a regular O2 sensor code?

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