What Does P1155 Mean?
This manufacturer-specific code signals a malfunction in the heater circuit of the air/fuel ratio sensor on bank 1, sensor 1. The heater element is critical to bring the wideband A/F sensor to operating temperature quickly after cold start. When the heater circuit fails, the sensor takes much longer to reach closed-loop operation, resulting in extended open-loop fueling with richer mixtures and higher emissions.
Common Causes
35%
Burned-out or internally open A/F sensor heater element
25%
Open circuit in the heater power supply wiring or blown heater fuse
20%
Corroded or water-damaged connector at the A/F sensor
12%
Failed heater control relay or PCM heater driver transistor
8%
High-resistance ground connection for the sensor heater circuit
Diagnostic Steps
1
Measure heater circuit resistance at the A/F sensor connector (disconnect sensor); typical range is 2-14 ohms depending on manufacturer. An open reading confirms a failed heater element.
2
Check for battery voltage at the heater power supply wire with the key on; verify the heater fuse is intact.
3
Test the PCM ground-side control of the heater circuit using a test light or current probe while commanding the heater on.
4
Inspect the sensor connector and wiring for water intrusion, corrosion, or heat damage from exhaust proximity.
5
Replace the bank 1 sensor 1 A/F sensor if heater resistance is out of specification.
Estimated Repair Cost
$150 - $400
Parts + labor, varies by vehicle and location
This manufacturer-specific code signals a malfunction in the heater circuit of the air/fuel ratio sensor on bank 1, sensor 1. The heater element is critical to bring the wideband A/F sensor to operating temperature quickly after cold start. When the heater circuit fails, the sensor takes much longer...
The most common cause of P1155 (Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)) is: Burned-out or internally open A/F sensor heater element
Typical repair costs for P1155 range from $150 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
No immediate safety hazard. Extended cold-start enrichment increases fuel consumption and emissions, and prolonged operation may accelerate catalytic converter degradation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1155 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel / Air Metering
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
