P0164
O2 Sensor Circuit High Voltage (Bank 2, Sensor 3)
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P0164 means the PCM has detected a persistently high voltage signal from the third oxygen sensor on Bank 2. This sensor monitors the secondary catalytic converter and should oscillate between approximately 0.1V and 0.9V. When the voltage remains consistently above the upper threshold, the PCM stores this code.
As with other Sensor 3 codes, the driveability impact is typically minimal because this sensor is primarily an emissions monitor for the secondary catalytic converter. However, if the high voltage is caused by a genuine rich running condition rather than just a sensor failure, you may notice increased fuel consumption, a fuel smell from the exhaust, or in severe cases, black smoke.
Check for companion codes — if P0172 or P0175 (system too rich) are also present, the problem likely lies in the fuel system rather than the sensor itself. If P0164 appears alone, the sensor or its wiring is the most probable cause. Replace the sensor and clear the code. If the code returns, further wiring diagnosis is warranted.
Severity
Symptoms
- •Check Engine Light is on
- •Slightly decreased fuel economy
- •Possible faint fuel smell from exhaust
- •Minor increase in exhaust emissions
- •No significant driveability symptoms
- •Failed emissions inspection
Likely Causes
The third oxygen sensor on Bank 2 has failed and is producing a constant high voltage output, incorrectly indicating a rich exhaust condition downstream of the secondary catalytic converter.
A wiring fault is shorting the sensor signal wire to a power source, causing an artificially high voltage reading at the PCM.
A genuine rich running condition — from leaking injectors, high fuel pressure, or other fuel system issues — is causing high O2 readings at the third sensor.
The sensor element has been contaminated by silicone sealants, coolant leaks, or excessive oil burning, causing it to produce an erroneously high voltage.
The PCM is supplying an incorrect reference or bias voltage to the sensor circuit.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the Bank 2 Sensor 3 oxygen sensor
- Repair shorted wiring in the sensor signal circuit
- Diagnose and resolve rich fuel condition if present
- Address root cause of sensor contamination (oil leaks, coolant leaks)