What does the P0055 fault code mean?
The P0055 fault code, applicable to all car manufacturers, means “HO2S Heater Resistance (Bank 1, Sensor 3)“.
Background Information: The function of the oxygen sensor is to measure the oxygen content in the engine exhaust to correct the fuel injection amount, thereby achieving the optimal air-fuel ratio for the engine. In OBD fault codes, you will often see references to which bank and which sensor. Bank 1 refers to the bank containing cylinder 1, and the other bank is Bank 2. Regardless of the bank, the first sensor always refers to the upstream oxygen sensor (before the catalytic converter), and the second sensor always refers to the downstream oxygen sensor (after the catalytic converter). This fault code indicates that the current in the heated oxygen sensor heater control circuit is too low or too high.
Symptoms of the P0055 error code:
- Engine misfire
- Increased fuel consumption
- Unstable engine operation
- Difficulty starting a cold engine
- Failure of emission tests
Main causes of the P0055 error code:
- Damaged oxygen sensor heating element
- Blown circuit fuse
- Open or short circuit in the wiring
- Oxidation or contamination of the connector
- Controller failure (ECU)
P0055 error code in different vehicles:
Toyota P0055: In some Toyota models, the error is often related to a broken wire near the exhaust manifold.
Nissan P0055: Nissan vehicles frequently experience sensor failures after 100,000 kilometers, especially with frequent engine overheating.
Ford P0055: In Ford vehicles, this error may be caused by aging sensors or unreliable non-OEM replacement parts.
Volkswagen P0055: Volkswagen vehicles often experience connector oxidation problems in humid climates.
Hyundai P0055: Hyundai vehicles may experience blown heater circuit fuses due to power surges.
How to diagnose the P0055 error code?
Step 1: Read the error codes using an OBD2 scanner
Step 2: Check the HO2S sensor (Bank 1, Sensor 3) for damage
Step 3: Check if the heater resistance is within specifications (usually 5-14 ohms)
Step 4: Check the wiring, fuses, and relays
Step 5: Clear the fault codes and perform a test drive to check if the error recurs
| Possible Causes | How to Check？ |
|---|---|
| Sensor heater burned out | Measure resistance with a multimeter |
| Broken wire | Visual inspection and continuity test |
| Poor connector contact | Clean and inspect the connector |
| Blown fuse | Check the fuse box |
| ECU malfunction | Oscilloscope check or replacement |
Tools needed: OBD2 scanner, multimeter, electrical tape, contact cleaner
How to fix P0055 error code? (Troubleshooting)
Simple repair methods
- Clear the error code and test drive
- Check and replace the fuse
- Clean or secure the connector
In-depth diagnostic and repair solutions
- Replace the oxygen sensor
- Repair or replace damaged wiring
- Check and repair the engine control unit
| Symptoms | Possible Solutions |
|---|---|
| Check engine light | Read and reset fault codes, check the sensor |
| High fuel consumption | Replace HO2S, fuel system check |
| Unstable engine operation | Wiring and sensor diagnostics |
P0055 Error Frequently Asked Questions
Is it possible to drive with a P0055 error?
It is not recommended, as the fuel management system will be affected, increasing the load on the catalytic converter, potentially leading to its failure.
Does the P0055 error affect fuel consumption?
Yes, a faulty oxygen sensor heater can cause incorrect readings, leading to the engine using the wrong fuel mixture ratio, thus increasing fuel consumption.
Can I fix the P0055 error myself?
Yes, if you have basic skills and tools, you can replace the sensor or check the wiring. However, if in doubt, it’s best to consult a specialist.
The P0055 error appears intermittently. What should I do?
Intermittent occurrences may indicate a non-permanent contact or wiring problem. A comprehensive diagnostic is recommended.
If the problem is with the heater, do I need to replace the entire sensor?
Yes, the heater is built into the sensor, so replacement will involve a brand new component.
Related OBD2 Errors:
P0030 – HO2S Heater Control Circuit (Bank 1, Sensor 1)
P0051 – HO2S Heater Control Circuit Low (Bank 2, Sensor 1)
P0135 – O2 Sensor Heater Circuit (Bank 1, Sensor 1)
Important! Even if the engine is running normally, ignoring these errors can lead to long-term consequences: catalytic converter failure and reduced lifespan of other system components. Don’t rush to replace the sensor. First, check the wiring and fuses. This can save you significant repair costs.