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:
- Luxury vehicles
- Vehicles with dual catalytic converters
- Advanced emissions systems
- Some diesel engines
- Vehicles equipped with three oxygen sensors per bank
Common causes of P0064 include:
- Open heater circuit
- Failed oxygen sensor heater
- Broken wiring
- Loose connector
- Corroded terminals
- Blown heater fuse
- Failed heater relay
- Incorrect replacement sensor
- ECM driver failure (rare)
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:
- Complete OBD-II Code Library: https://my.prostreetonline.com/dtc-obdii/
- Body B-Code Library: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- Chassis C-Code Library: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
P0064 Quick Facts
| Item | Information |
|---|---|
| OBD-II Code | P0064 |
| Description | HO2S Heater Control Circuit High Bank 2 Sensor 3 |
| Category | Powertrain |
| System | Emissions |
| Sensor | Bank 2 Sensor 3 |
| Typical Location | After Secondary Catalytic Converter |
| Severity | Low |
| 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 heater element opens internally
- A connector becomes disconnected
- A wire breaks
- The heater fuse loses contact
- The ECM can no longer complete the circuit
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:
- Monitor catalyst efficiency
- Verify emissions performance
- Complete readiness monitors
- Detect catalyst deterioration
- Confirm downstream oxygen content
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:
- Warm up quickly
- Reduce cold-start emissions
- Begin catalyst monitoring sooner
- Complete emissions readiness monitors
- Improve diagnostic accuracy
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:
- Battery voltage
- Heater fuse
- Heater relay
- Oxygen sensor heater element
- ECM-controlled ground
- Wiring harness
- Electrical connectors
When commanded on, battery voltage flows through the heater element.
The ECM controls the ground side and monitors:
- Circuit voltage
- Current flow
- Heater resistance
- Warm-up speed
- Sensor response
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:
- Open heater element
- Broken wiring
- Loose connector
- Corroded terminals
- Failed relay
- Blown fuse
- Internal ECM driver fault
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:
- Commanded heater operation
- Circuit voltage
- Heater current
- Warm-up time
- Sensor response
P0064 may be stored when:
- Voltage remains too high
- Current flow is insufficient
- Heater fails to respond
- Warm-up takes too long
- The heater circuit remains open
Some vehicles require multiple failed drive cycles before illuminating the Check Engine Light.
P0062 vs P0063 vs P0064
| Code | Description |
| P0062 | Heater Control Circuit Bank 2 Sensor 3 |
| P0063 | Heater Control Circuit Low Bank 2 Sensor 3 |
| P0064 | Heater Control Circuit High Bank 2 Sensor 3 |
Generally:
- P0062 indicates a general heater circuit fault.
- P0063 indicates low voltage or excessive current.
- P0064 indicates high voltage or insufficient current.
Symptoms of P0064
Common symptoms include:
- Check Engine Light
- Failed emissions inspection
- Catalyst monitor incomplete
- Increased cold-start emissions
- Oxygen sensor monitor incomplete
Most vehicles will not experience:
- Poor acceleration
- Rough idle
- Misfires
- Major fuel economy changes
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:
- Broken conductors
- Heat damage
- Chafing
- Rodent damage
3. Loose Connector
A partially disconnected connector creates an open circuit.
Inspect for:
- Broken locking tabs
- Loose terminals
- Bent pins
4. Corroded Connector
Moisture intrusion may cause:
- Green corrosion
- High resistance
- Open terminals
- Water damage
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:
- Battery
- Alternator
- Ground straps
10. ECM Driver Failure
Rare.
Only suspect the ECM after verifying:
- Sensor
- Wiring
- Fuse
- Relay
- Connectors
- Power supply
Is P0064 Serious?
P0064 is considered a low-severity diagnostic trouble code.
Most vehicles remain safe to drive.
However, delaying repairs can result in:
- Failed emissions testing
- Increased emissions
- Incomplete readiness monitors
- Additional heater circuit faults
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:
- P0062
- P0063
- P0061
- Other oxygen sensor heater codes
- Battery voltage codes
Record freeze-frame data.
Step 2: Verify Bank 2 Sensor 3
Confirm the vehicle actually uses:
- Bank 2
- Sensor 3
- A dedicated heater circuit
Step 3: Locate the Sensor
Follow the Bank 2 exhaust system downstream until Sensor 3 is identified.
Step 4: Inspect Wiring
Look for:
- Broken wires
- Melted insulation
- Chafing
- Loose routing clips
- Exhaust damage
Step 5: Inspect Connector
Check for:
- Corrosion
- Loose pins
- Bent terminals
- Broken locking tabs
- Moisture
Step 6: Check Heater Fuse
Inspect the oxygen sensor heater fuse.
If blown:
- Determine why
- Inspect wiring
- Test the sensor
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:
- Relay
- Fuse
- Power wiring
Step 8: Measure Heater Resistance
Disconnect the sensor.
Measure heater resistance.
Possible results include:
- Infinite resistance (open heater)
- Excessively high resistance
- Normal resistance
Compare readings to manufacturer specifications.
Step 9: Check the Control Circuit
Inspect the ECM control wire for:
- Continuity
- Opens
- Excessive resistance
- Loose terminals
Step 10: Command Heater Operation
Using a scan tool, command the heater on.
Monitor:
- Current draw
- Voltage
- Warm-up speed
- Sensor response
Step 11: Replace the Sensor if Necessary
Replace Bank 2 Sensor 3 if testing confirms:
- Open heater
- Heater resistance outside specification
- Failure to warm properly
Use an OEM-quality direct-fit sensor.
Step 12: Verify Repairs
After repairs:
- Clear all DTCs.
- Perform a cold start.
- Monitor heater operation.
- Complete the drive cycle.
- Verify readiness monitors complete.
- Confirm P0064 does not return.
Common Repairs and Costs
| Repair | Estimated 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:
- Replacing the wrong oxygen sensor
- Assuming every vehicle has Sensor 3
- Ignoring an open heater element
- Skipping resistance testing
- Installing universal oxygen sensors
- Missing broken wiring behind heat shields
- Condemning the ECM before testing the circuit
Vehicles Commonly Affected
P0064 may appear on certain:
- Audi
- BMW
- Mercedes-Benz
- Volkswagen
- Toyota
- Lexus
- Nissan
- Infiniti
- General Motors trucks
- Diesel applications
Exact sensor layouts vary by manufacturer.
How to Prevent P0064
Reduce the likelihood of P0064 by:
- Using OEM-quality oxygen sensors
- Securing wiring away from hot exhaust components
- Reinstalling heat shields
- Maintaining charging-system health
- Repairing exhaust leaks promptly
- Inspecting connectors during exhaust work
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:
- Open heater element
- Broken wiring
- Corroded connector
- Blown fuse
- Failed relay
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.
Related Articles
Bank 2 Sensor 3 Heater Codes
- P0061 Code Explained: HO2S Heater Resistance Bank 2 Sensor 3
- P0062 Code Explained: HO2S Heater Control Circuit Bank 2 Sensor 3
- P0063 Code Explained: HO2S Heater Control Circuit Low Bank 2 Sensor 3
Browse the complete Pro Street diagnostic libraries:
- Complete OBD-II Guide: https://my.prostreetonline.com/dtc-obdii/
- B-Code Guide: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- C-Code Guide: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
