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P0064 Code Explained: HO2S Heater Control Circuit High Bank 2 Sensor 3 Causes, Symptoms & Fixes

P0064 code displayed on an OBD-II scanner with the Bank 2 Sensor 3 oxygen sensor and open heater circuit highlighted behind the catalytic converter.

If your OBD-II scanner displays P0064, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a high-voltage condition in the heated oxygen sensor (HO2S) heater control circuit for Bank 2 Sensor 3.

The generic SAE definition for P0064 is:

HO2S Heater Control Circuit High Bank 2 Sensor 3

This code indicates that the ECM has detected higher-than-expected voltage or lower-than-expected current in the heater control circuit for the third oxygen sensor on Bank 2.

Bank 2 Sensor 3 is typically found after the secondary catalytic converter on the side of the engine opposite cylinder number one. Since this sensor is primarily responsible for catalyst efficiency monitoring rather than fuel control, most drivers won’t notice immediate performance issues.

Not every vehicle uses a Bank 2 Sensor 3. P0064 is generally found on:

Common causes of P0064 include:

Although P0064 usually doesn’t create serious drivability problems, it can prevent catalyst monitoring from completing and cause the vehicle to fail emissions testing.

For additional diagnostic information, visit:

P0064 Quick Facts

ItemInformation
OBD-II CodeP0064
DescriptionHO2S Heater Control Circuit High Bank 2 Sensor 3
CategoryPowertrain
SystemEmissions
SensorBank 2 Sensor 3
Typical LocationAfter Secondary Catalytic Converter
SeverityLow
Safe to Drive?Yes
Typical Repair Cost$75–650

What Does P0064 Mean?

P0064 indicates the ECM has detected higher-than-expected voltage in the heater control circuit for Bank 2 Sensor 3.

In many systems, a high-voltage condition occurs because current is not flowing through the heater as expected.

This commonly happens when:

The ECM expects a specific amount of current whenever it commands the heater on.

If current is missing, voltage remains high and P0064 is stored.

What Is Bank 2 Sensor 3?

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

Sensor 3 is normally located after a secondary catalytic converter.

Depending on vehicle design, it helps the ECM:

Unlike upstream oxygen sensors, Sensor 3 generally does not control fuel delivery.

Why Does Sensor 3 Need a Heater?

An oxygen sensor must reach approximately 600°F (315°C) before it can produce reliable readings.

The internal heater allows the sensor to:

Without the heater, the sensor eventually reaches temperature using exhaust heat alone, but often too slowly for the ECM’s self-tests.

How the Heater Circuit Works

A typical heater circuit contains:

When commanded on, battery voltage flows through the heater element.

The ECM controls the ground side and monitors:

If voltage remains high because current cannot flow, P0064 is stored.

What Does “Circuit High” Mean?

“Circuit High” usually indicates the ECM is seeing too much voltage on the control circuit.

This commonly results from:

Unlike P0063, which indicates excessive current or a short to ground, P0064 usually points toward an open circuit.

How the ECM Detects P0064

The ECM performs heater tests during cold starts.

It monitors:

P0064 may be stored when:

Some vehicles require multiple failed drive cycles before illuminating the Check Engine Light.

P0062 vs P0063 vs P0064

CodeDescription
P0062Heater Control Circuit Bank 2 Sensor 3
P0063Heater Control Circuit Low Bank 2 Sensor 3
P0064Heater Control Circuit High Bank 2 Sensor 3

Generally:

Symptoms of P0064

Common symptoms include:

Most vehicles will not experience:

Common Causes of P0064

1. Failed Heater Element

The heater inside the oxygen sensor burns open.

This is the most common cause.

2. Broken Heater Wiring

Broken wiring can interrupt current flow.

Inspect for:

3. Loose Connector

A partially disconnected connector creates an open circuit.

Inspect for:

4. Corroded Connector

Moisture intrusion may cause:

5. Blown Heater Fuse

Many manufacturers use a shared heater fuse.

If blown, multiple heater codes may appear simultaneously.

6. Failed Heater Relay

A faulty relay may interrupt power to multiple oxygen sensor heaters.

7. Incorrect Replacement Sensor

Universal sensors sometimes use heater elements with incorrect specifications.

OEM-quality direct-fit sensors are recommended.

8. Open Ground Circuit

A broken ECM control wire prevents current flow through the heater.

9. Charging System Issues

Although uncommon, unstable system voltage can affect heater diagnostics.

Inspect:

10. ECM Driver Failure

Rare.

Only suspect the ECM after verifying:

Is P0064 Serious?

P0064 is considered a low-severity diagnostic trouble code.

Most vehicles remain safe to drive.

However, delaying repairs can result in:

Can You Drive With P0064?

Yes.

Most drivers notice no drivability problems.

The vehicle usually operates normally because Sensor 3 monitors emissions rather than engine performance.

Still, ignoring the code may leave your readiness monitors permanently unfinished—which is a creative way to discover your emissions appointment was scheduled too soon.

How to Diagnose P0064

Step 1: Scan for Additional Codes

Look for:

Record freeze-frame data.

Step 2: Verify Bank 2 Sensor 3

Confirm the vehicle actually uses:

Step 3: Locate the Sensor

Follow the Bank 2 exhaust system downstream until Sensor 3 is identified.

Step 4: Inspect Wiring

Look for:

Step 5: Inspect Connector

Check for:

Step 6: Check Heater Fuse

Inspect the oxygen sensor heater fuse.

If blown:

Do not repeatedly replace fuses without diagnosing the circuit.

Step 7: Verify Battery Voltage

Check for battery voltage at the heater connector.

If voltage is missing, inspect:

Step 8: Measure Heater Resistance

Disconnect the sensor.

Measure heater resistance.

Possible results include:

Compare readings to manufacturer specifications.

Step 9: Check the Control Circuit

Inspect the ECM control wire for:

Step 10: Command Heater Operation

Using a scan tool, command the heater on.

Monitor:

Step 11: Replace the Sensor if Necessary

Replace Bank 2 Sensor 3 if testing confirms:

Use an OEM-quality direct-fit sensor.

Step 12: Verify Repairs

After repairs:

  1. Clear all DTCs.
  2. Perform a cold start.
  3. Monitor heater operation.
  4. Complete the drive cycle.
  5. Verify readiness monitors complete.
  6. Confirm P0064 does not return.

Common Repairs and Costs

RepairEstimated Cost
Oxygen sensor replacement$175–600
Wiring repair$100–450
Connector replacement$75–275
Heater relay replacement$50–225
Heater fuse replacement$10–50
Harness repair$150–650
ECM diagnosis$150–500
ECM replacement$1,000–2,500+

Common Diagnostic Mistakes

Avoid these mistakes:

Vehicles Commonly Affected

P0064 may appear on certain:

Exact sensor layouts vary by manufacturer.

How to Prevent P0064

Reduce the likelihood of P0064 by:

Frequently Asked Questions

What does P0064 mean?

P0064 indicates the ECM has detected a high-voltage condition in the Bank 2 Sensor 3 heater control circuit.

Is P0064 serious?

Usually not.

Most vehicles remain safe to drive.

Can I drive with P0064?

Yes.

Most drivers notice no performance issues.

What commonly causes P0064?

The most common causes include:

Will replacing the oxygen sensor fix P0064?

Often, yes.

However, wiring, connectors, fuse, and relay should always be inspected first.

What is the difference between P0063 and P0064?

P0063 indicates a low-voltage heater circuit.

P0064 indicates a high-voltage heater circuit.

Can P0064 cause an emissions failure?

Yes.

Incomplete readiness monitors commonly prevent emissions testing from passing.

Final Thoughts

The P0064 code indicates the ECM has detected higher-than-normal voltage in the Bank 2 Sensor 3 heater control circuit, usually because the heater circuit has opened or current is no longer flowing as expected. The most common causes are a failed oxygen sensor heater, broken wiring, corroded connectors, or a blown heater fuse.

Because Bank 2 Sensor 3 primarily monitors catalyst efficiency, most drivers won’t notice any difference in performance. However, repairing the fault restores proper emissions monitoring, completes OBD-II readiness tests, and prevents additional heater circuit codes from appearing later. As with any oxygen sensor diagnosis, testing the heater circuit before replacing parts is considerably less expensive than discovering the new sensor wasn’t the problem after all.

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