My Pro Street

P0055 Code Explained: HO2S Heater Resistance Bank 2 Sensor 2 Causes, Symptoms & Fixes

P0055 code displayed on an OBD-II scanner with the downstream Bank 2 Sensor 2 oxygen sensor highlighted behind the catalytic converter.

If your OBD-II scanner displays P0055, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected that the heater resistance of the Heated Oxygen Sensor (HO2S) on Bank 2 Sensor 2 is outside the manufacturer’s expected operating range.

The generic SAE definition for P0055 is:

HO2S Heater Resistance Bank 2 Sensor 2

Unlike heater control circuit codes that monitor voltage or current, P0055 specifically indicates the ECM has determined the internal heater element resistance is either too high, too low, or completely outside specification.

Bank 2 Sensor 2 is the downstream oxygen sensor located after the catalytic converter on the side of the engine opposite cylinder number one.

Depending on the manufacturer, this sensor may also be called:

Common causes of P0055 include:

Although P0055 rarely causes drivability issues, it can prevent catalyst monitoring, increase emissions, and cause your vehicle to fail an emissions inspection.

For additional diagnostic information, visit:

P0055 Quick Facts

ItemInformation
OBD-II CodeP0055
DescriptionHO2S Heater Resistance Bank 2 Sensor 2
CategoryPowertrain
SystemEmissions
SensorBank 2 Sensor 2
Sensor LocationDownstream (After Catalytic Converter)
SeverityLow
Safe to Drive?Yes
Typical Repair Cost$100–600

What Does P0055 Mean?

P0055 means the ECM has detected that the electrical resistance of the heater inside the downstream oxygen sensor on Bank 2 is outside the calibrated operating range.

Every heated oxygen sensor contains an internal electric heating element.

The heater allows the sensor to:

If the heater resistance changes beyond acceptable limits, the ECM stores P0055.

Unlike P0039 or P0056, P0055 does not necessarily indicate a wiring failure—it specifically points toward the heater element or excessive circuit resistance.

What Is Bank 2 Sensor 2?

Bank 2 refers to the side of the engine that does not contain cylinder number one.

Sensor 2 is the oxygen sensor positioned after the catalytic converter.

Its primary responsibilities include:

Unlike upstream oxygen sensors, the downstream sensor generally does not directly control fuel trims.

Why Does the Downstream Oxygen Sensor Have a Heater?

Modern emissions regulations require catalytic converter monitoring shortly after startup.

Without an electric heater, the downstream oxygen sensor would require significantly more time before producing reliable readings.

The heater allows the ECM to:

How the Heater Resistance Is Monitored

The ECM continuously evaluates:

The ECM knows approximately what resistance the heater should have.

If resistance becomes:

P0055 is stored.

This diagnostic is different from heater circuit codes because the circuit itself may still function electrically while the heater element has degraded internally.

P0055 vs Related Codes

CodeDescription
P0036Heater Control Circuit Bank 1 Sensor 2
P0037Heater Circuit Low Bank 1 Sensor 2
P0038Heater Circuit High Bank 1 Sensor 2
P0054Heater Resistance Bank 1 Sensor 2
P0055Heater Resistance Bank 2 Sensor 2
P0056Heater Control Circuit Bank 2 Sensor 2

Generally:

Symptoms of P0055

Common symptoms include:

Most drivers notice no change in performance.

Common Causes of P0055

1. Aging Heater Element

The internal heater gradually changes resistance after years of repeated heating and cooling cycles.

This is the most common cause.

2. Failed Oxygen Sensor

Internal heater damage eventually moves resistance outside specification.

Replacement is usually required.

3. Open Heater Element

The heater may fail completely, resulting in infinite resistance.

4. Corroded Connector

Connector corrosion increases circuit resistance.

Inspect for:

5. Damaged Wiring

Inspect the harness for:

6. Poor Ground

High resistance in the ground circuit can affect heater performance.

Verify ground integrity before replacing the sensor.

7. Incorrect Replacement Sensor

Universal oxygen sensors often use heater elements that differ from OEM specifications.

Direct-fit sensors are strongly recommended.

8. Weak Charging System

Low charging voltage may interfere with heater diagnostics.

Inspect:

9. Failed Heater Relay

Some vehicles power several heater circuits through one relay.

A weak relay may reduce heater performance.

10. ECM Driver Failure

Extremely uncommon.

Only suspect the ECM after verifying:

Is P0055 Serious?

P0055 is considered a low-severity diagnostic trouble code.

The vehicle generally remains safe to drive.

However, ignoring the code can result in:

Can You Drive With P0055?

Yes.

Because Bank 2 Sensor 2 primarily monitors catalyst performance rather than fuel delivery, most vehicles continue driving normally.

The only thing likely to suffer immediately is your emissions readiness monitor—and perhaps your patience when inspection time arrives.

How to Diagnose P0055

Step 1: Scan for Additional Codes

Look for:

Record freeze-frame data before clearing anything.

Step 2: Locate Bank 2 Sensor 2

Confirm:

Replacing the wrong sensor remains surprisingly common.

Step 3: Inspect Wiring

Look for:

Pay close attention to wiring near the catalytic converter.

Step 4: Inspect Connector

Inspect for:

Step 5: Measure Heater Resistance

Disconnect the sensor.

Measure resistance across the heater terminals.

Possible results include:

Compare measurements with manufacturer specifications.

Step 6: Verify Power Supply

Check:

Step 7: Perform Voltage Drop Testing

Voltage-drop testing helps identify:

Step 8: Compare With Bank 1 Sensor 2

If both downstream sensors are identical, compare:

Differences often identify the faulty sensor.

Step 9: Replace the Sensor if Necessary

If heater resistance is outside specification, replace Bank 2 Sensor 2 with a quality OEM-equivalent direct-fit sensor.

Step 10: Verify Repair

After repairs:

  1. Clear all DTCs.
  2. Perform a cold start.
  3. Monitor heater operation.
  4. Complete a drive cycle.
  5. Confirm readiness monitors complete.
  6. Verify P0055 does not return.

Common Repairs and Costs

RepairEstimated Cost
Oxygen sensor replacement$150–500
Wiring repair$100–400
Connector replacement$75–250
Heater relay replacement$50–200
Fuse replacement$10–50
Battery or charging repair$150–400
ECM replacement$1,000–2,500+

Common Diagnostic Mistakes

Avoid these common mistakes:

Vehicles Commonly Affected

P0055 commonly appears on:

Exact heater specifications vary by manufacturer.

How to Prevent P0055

Reduce the likelihood of P0055 by:

Frequently Asked Questions

What does P0055 mean?

P0055 indicates the heater resistance of the Bank 2 Sensor 2 oxygen sensor is outside the manufacturer’s specification.

Is P0055 serious?

Usually not.

Most vehicles continue operating normally.

Can I drive with P0055?

Yes.

The downstream oxygen sensor primarily monitors catalytic converter performance rather than fuel delivery.

What causes P0055?

The most common causes include:

Will replacing the oxygen sensor fix P0055?

In most cases, yes.

However, wiring and connectors should always be inspected before replacing components.

Is P0055 the same as P0056?

No.

P0055 monitors heater resistance.

P0056 monitors the heater control circuit.

Does P0055 affect fuel economy?

Usually very little.

The downstream sensor has minimal influence on fuel control.

Can P0055 cause a failed emissions inspection?

Yes.

If readiness monitors cannot complete or catalyst monitoring is affected, the vehicle may fail inspection.

Final Thoughts

The P0055 code indicates the ECM has detected abnormal heater resistance in the Bank 2 Sensor 2 heated oxygen sensor. In most cases, this points to an aging heater element inside the downstream oxygen sensor, although damaged wiring, corroded connectors, poor electrical connections, and incorrect replacement sensors can produce the same fault.

Because the downstream sensor primarily monitors catalytic converter performance, most drivers won’t notice any changes in engine performance. However, ignoring P0055 can delay readiness monitors, increase emissions, and prevent the vehicle from passing an emissions inspection. A careful inspection of the wiring, connector, and heater resistance before replacing the sensor will help ensure an accurate repair.

Related Articles

Bank 2 Sensor 2 Heater Codes

Heater Resistance Codes

Browse the complete Pro Street diagnostic libraries:

Exit mobile version