The last oxygen sensor on bank 2 should rarely see a rich exhaust, since two catalytic converters clean the gas before it gets there. A high reading often points to an electrical fault rather than a fuel problem. A P0164 code means the bank 2 sensor 3 voltage stayed too high for too long.
This guide explains what pushes the reading high, how to test the circuit and which repairs fix it.
P0164 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 1 | Fuel and air metering | The fault involves the sensors that measure air and fuel. |
| 64 | Specific fault | O2 Sensor Circuit High Voltage (Bank 2 Sensor 3) |
What the P0164 Code Means
The SAE J2012 standard defines the P0164 code as O2 Sensor Circuit High Voltage (Bank 2 Sensor 3). Sensor 3 sits after the second catalytic converter on the side of the engine without cylinder 1.
A zirconia oxygen sensor cannot make much more than about 1.0 volt on its own. When the powertrain control module (PCM) sees bank 2 sensor 3 above that level, or stuck high when it should drop, it sets the code.
Many PCMs check this during deceleration fuel cutoff. With the injectors off, the exhaust turns lean, and sensor 3 should fall below about 0.2 volt. A reading that stays high fails the test.
Symptoms of a High Bank 2 Sensor 3 Reading
Sensor 3 does not control fuel on most vehicles, so the engine usually runs normally. Signs of a P0164 code include:
- Check engine light on
- Catalyst monitor that will not complete
- Failed emissions test
- Fuel smell or black smoke if bank 2 runs rich
Common Causes of the P0164 Code
Wiring shorts and sensor faults cause most cases. These are the usual causes:
- Signal wire shorted to the heater wire. Heat can melt the insulation inside the sensor cable.
- Signal wire shorted to another power source. Damaged wiring under the vehicle can touch a live wire.
- Failed oxygen sensor. An internal fault locks the output high.
- Water in the connector. Moisture can bridge the pins.
- Severe rich condition on bank 2. A leaking injector can overwhelm both converters.
- Contaminated sensor. Oil or coolant deposits affect the reading.
How to Test for the P0164 Code
You need a scan tool with live data, a multimeter and a wiring diagram. Drive until all converters are fully hot.
Do a Coasting Test
Graph bank 1 sensor 3 and bank 2 sensor 3 while you accelerate to about 40 mph, then lift off the gas and coast. Both should fall below about 0.2 volt within several seconds. If bank 1 drops and bank 2 stays high, the bank 2 sensor is shorted or failed.
Check Fuel Trims
Look at bank 2 fuel trims. Large negative numbers mean the PCM is pulling fuel from that side to fix a rich condition. If trims are normal, the problem is almost certainly in the sensor or wiring.
Test for a Short
Unplug the sensor and turn the key on. The signal wire on the vehicle side should read low, often about 0.45 volt or less. A reading near battery voltage means a short to power. On the sensor itself, check for continuity between the signal and heater pins. Any connection means an internal short.
Fixing the P0164 Code
Base the repair on your test results. Clear the code and drive until the monitors complete.
- Replace bank 2 sensor 3 if it shows an internal short or stays high while coasting.
- Repair shorted wiring under the vehicle.
- Dry and clean the connector, then add dielectric grease to the seal.
- Fix any rich condition on bank 2, such as a leaking injector.
When a short is the cause, look closely where the wiring passes near the exhaust or crosses a frame rail. Heat can melt the insulation between the signal and heater wires. If the damage is in the sensor lead, a new sensor fixes both problems at once.
Repair Cost Breakdown
The fix for a P0164 code is often a sensor or a small wiring repair. Here are typical costs.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Bank 2 sensor 3 replacement | $30 to $130 | $120 to $350 |
| Wiring repair | $10 to $30 | $100 to $300 |
| Connector cleaning | $10 to $15 | $50 to $100 |
| Fuel injector replacement (each) | $50 to $200 | $150 to $500 |
Is It Safe to Drive with a P0164 Code?
In most cases, yes. The engine runs on the front sensors and drives normally. You will fail an emissions test, though.
If bank 2 truly runs rich, unburned fuel can overheat its converters. Watch for a fuel smell or poor mileage, and fix any rich condition quickly.
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0161 | O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2) |
| P0162 | O2 Sensor Circuit Malfunction (Bank 2 Sensor 3) |
| P0163 | O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3) |
| P0165 | O2 Sensor Circuit Slow Response (Bank 2 Sensor 3) |
| P0166 | O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3) |
Correcting a High Bank 2 Sensor 3 Reading
A P0164 code means the bank 2 sensor 3 voltage stays too high. Shorted wiring and failed sensors cause most cases, with rich running less common.
- Compare both sensor 3 readings during a coast.
- Check bank 2 fuel trims for a rich condition.
- Test for a short between the signal and heater wires.
- Replace the sensor if it stays high or is shorted inside.
Frequently Asked Questions
Does a High Sensor 3 Reading Mean a Bad Converter?
Rarely. A worn converter usually lets the downstream signal switch more, which sets an efficiency code. A reading stuck high points to a short, a failed sensor or a rich engine. Test those first.
Why Does Water Cause Sensor Codes?
Sensor 3 connectors sit low under the vehicle, where road spray reaches them. Water inside a connector can link the signal pin to the heater pin and raise the voltage. Cleaning, drying and sealing the connector often fixes the problem.
Can a Rich Engine Damage the Converters?
Yes, over time. Extra fuel burns inside the converters and raises their temperature. Severe overheating can melt the inside of a converter and block the exhaust. If the engine really runs rich on bank 2, fix the fuel problem right away.
How Do I Know I Have the Right Sensor?
Bank 2 sensor 3 is the third sensor back on the side without cylinder 1, after the last converter. Your service manual shows the exact spot. Count carefully, since replacing sensor 2 by mistake will not clear the code.