DTC Advanced Diagnostics: P2256 (3.0L Engine)
DTC P2256: Front Air/Fuel Ratio (A/F) Sensor (Bank 2, Sensor 1) AFV Circuit High Voltage
General Description
The front air/fuel ratio (A/F) sensor (bank 2, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. The front A/F sensor (bank 2, sensor 1) transmits a signal to the powertrain control module (PCM), and the PCM controls fuel injection duration by comparing the target air/fuel ratio with the front A/F sensor (bank 2, sensor 1) signal. The front A/F sensor (bank 2, sensor 1) is composed of detection element, reference oxygen chamber, diffusion chamber, and heater, etc., and enables feedback control of all ranges. If the front A/F sensor (bank 2, sensor 1) signal AFVB2 is shorted to power, the terminal voltage shows abnormal value. If the AFVB2 terminal voltage is a set value for a specified duration, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 0.5 second or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | |
|---|---|
| Vehicle | ON mode |
Malfunction Threshold
The AFVB2 terminal voltage is 4.89 V or more for at least 0.5 second.
Possible Cause
- Front A/F sensor (bank 2, sensor 1) AFVB2 line short to power
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.