DTC P2251:00: Notes

DTC P2251:00	A/F sensor negative current control circuit open
DETECTION CONDITION	The PCM monitors the A/F sensor negative current control circuit voltage. If either of the following conditions are met while the engine running, the PCM determines that the A/F sensor negative current control circuit is open. MONITORING CONDITIONS Element impedance: more than 240 ohm Circuit voltage oscillation The PCM detects DTC P0030:00 or P0134:00 while pending code P2251:00 is stored. Diagnostic support note This is a continuous monitor (A/F sensor, HO2S). The MIL illuminates if PCM detects the above malfunctioning condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM. PENDING CODE is available if PCM detects the above malfunction conditions during first drive cycle. FREEZE FRAME DATA (Mode 2)/Snapshot data is available. The DTC is stored in the PCM memory
POSSIBLE CAUSE	A/F sensor connector or terminal malfunction PCM connector or terminal malfunction Open circuit in wiring harness between A/F sensor terminal D and PCM terminal 2AC A/F sensor malfunction PCM malfunction