In this blog, we’ll break down the causes, symptoms, and solutions for the P0155 code, and highlight how the iCarsoft CR MAX Vehicle Diagnostic Tool from www.icarsoft-us.com can assist in diagnosing and fixing this issue efficiently.

1. Understanding the P0155 Code

The P0155 code is a diagnostic trouble code (DTC) indicating "O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)." It means the Engine Control Unit (ECU) has detected a problem with the heating element in the oxygen sensor located before the catalytic converter on Bank 2 (the engine side without cylinder 1). This sensor’s heater ensures accurate readings by quickly reaching operating temperature. A malfunction delays this process, affecting fuel mixture adjustments and emissions.

2. Common Causes of P0155

Faulty O2 Sensor Heater
The heating element within the sensor may fail due to age, heat exposure, or internal damage.

Wiring or Connector Issues
Damaged, corroded, or disconnected wiring in the heater circuit can prevent proper operation.

Blown Fuse
A blown fuse in the O2 sensor heater circuit can cut power to the heater.

ECU Problems
Rarely, an ECU fault may disrupt the heater circuit’s control or power supply.

3. Why P0155 Happens

Sensor Wear
Continuous exposure to exhaust heat and contaminants can degrade the heater over time.

Electrical Faults
Shorts, opens, or high resistance in the circuit can disrupt heater function, triggering the code.

4. Vehicles Most Affected by P0155

The P0155 code can occur in any OBD-II vehicle with a heated oxygen sensor, including brands like Toyota, Ford, Honda, Chevrolet, and Nissan. European models such as BMW, Audi, and Volkswagen are also prone, especially those with high mileage or in regions with extreme weather.

5. How Serious Is P0155?

The P0155 code is moderately severe. A malfunctioning heater delays sensor readiness, leading to inaccurate fuel trim, reduced efficiency, and higher emissions. Prolonged issues may strain the catalytic converter, increasing repair costs.

6. Can You Drive with P0155?

Driving with P0155 is possible short-term, but not advisable long-term. You may notice poor fuel economy or rough idling, and untreated issues could damage the catalytic converter or fail emissions tests.

7. DIY Fixes for P0155

Sensor Replacement
Replace the faulty O2 sensor with a compatible unit, following your vehicle’s repair manual.

Wiring Repair
Inspect and fix damaged or corroded wiring and connectors in the heater circuit.

Fuse Check
Check and replace any blown fuses in the O2 sensor heater circuit.

8. Diagnosing P0155 Effectively

Scan Tool
Use the iCarsoft CR MAX to read the P0155 code and check heater circuit status via live data.

Multimeter Testing
Measure the heater’s resistance (typically 2-10 ohms) and voltage supply with a multimeter.

Visual Inspection
Examine the sensor, wiring, and fuse for physical damage or corrosion.

9. Repair Costs for P0155 Issues

Costs vary by repair. An O2 sensor replacement ranges from $50-$200, with labor adding $50-$150 (1-2 hours at $75/hour), totaling $100-$350. Wiring repairs cost $50-$200, while a fuse replacement is under $20.

10. Clearing the P0155 Code

Using a Scan Tool
Connect the iCarsoft CR MAX to clear the code and confirm the repair.

Battery Disconnection
Disconnect the battery for 5-10 minutes to reset the ECU, though this may not fix the root cause.

11. Preventing P0155 in the Future

Routine Maintenance
Follow your vehicle’s maintenance schedule to reduce wear on sensors and wiring.

Quality Parts
Use high-quality replacement sensors to ensure durability.

Wiring Protection
Shield heater circuit wiring from heat and moisture during repairs.

12. Key Notes on P0155

Related Codes
P0155 may appear with P0135 (Bank 1 equivalent) or other heater circuit codes. Diagnose all together.

Cold Weather Impact
The heater’s role is critical in cold starts, so P0155 may be more noticeable in winter.

13. Using a Diagnostic Tool for P0155

The iCarsoft CR MAX from www.icarsoft-us.com is your go-to tool for P0155. It reads the code, provides live heater data, and helps pinpoint faults. Post-repair, it clears the code and verifies the fix.

Need to resolve P0155 fast? The iCarsoft CR MAX streamlines diagnostics and restores performance.