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DTC codes / P2Axx · Hybrid propulsion / P2A08

P2A08O2 Sensor Negative Voltage Bank 1 Sensor 3

P2A08 means the engine computer has detected a negative voltage on the signal circuit of the third oxygen sensor on bank 1, which is the sensor after the catalytic converter on the side of the engine containing cylinder one. A healthy oxygen sensor produces a voltage between roughly 0.1 and 0.9 volts, so a reading below zero volts tells the computer that the signal circuit is being pulled to ground or that the sensor's internal reference has failed.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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