DTC P2251-00: A/F Sensor Negative Current Control Circuit Open: Notes

DTC P2251:00 DETECTION CONDITION AND POSSIBLE CAUSE

DTC P2251:00	A/F sensor negative current control circuit open
DETECTION CONDITION	The PCM monitors the A/F sensor signal voltage at the PCM terminal 2Z. If either of the following conditions are met, the PCM determines that the A/F sensor negative current control circuit is open. MONITORING CONDITIONS Circuit voltage oscillation or the PCM terminal 2Z voltage is below the specified. The PCM detects the DTC P0134:00 while the pending code P2251:00 is stored. A/F sensor element impedance: specified or more Diagnostic support note This is a continuous monitor (A/F sensor, HO2S). The check engine light illuminates if the PCM detects the above malfunction 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 the PCM detects the above malfunction condition during first drive cycle. FREEZE FRAME DATA (Mode 2)/Snapshot data is available. The DTC is stored in the PCM memory.
FAIL-SAFE FUNCTION	Fixes the duty value of the A/F sensor heater. Stops the fuel feedback control.
POSSIBLE CAUSE	A/F sensor connector or terminals malfunction PCM connector or terminals malfunction Open circuit in wiring harness between A/F sensor terminal 1B and PCM terminal 2AC A/F sensor malfunction PCM malfunction
Courtesy of MAZDA MOTORS CORP.