DTC P2251: Notes
DTC P2251 [L3] DETECTION CONDITIONS AND POSSIBLE CAUSES
| DTC P2251 |
A/F sensor negative current control circuit open |
| DETECTION CONDITION |
- The PCM monitors A/F sensor negative current control circuit voltage using the PCM terminal 2Z, 2AC and 2AD voltage. If the either of the following condition is met, the PCM determines that the A/F sensor negative current control circuit is open.
- The A/F sensor element impedance above 240 ohm
for 10 s.
- The PCM 2Z voltage oscillation frequency is above threshold for 2 s.
- The PCM detect DTC P0030 or P0134 while the pending code. P2251 is stored.
MONITORING CONDITION
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 the first drive cycle.
- FREEZE FRAME DATA (Mode 2/Mode 12) is available.
- DTC is stored in the PCM memory
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| POSSIBLE CAUSE |
- A/F sensor connector or terminal malfunction
- PCM connector or terminal malfunction
- Open circuit between PCM terminal 2AC and A/F sensor terminal D
- A/F sensor malfunction
- A/F sensor heater can not be controlled
- PCM malfunction
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 Courtesy of MAZDA MOTORS CORP.
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