SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSMAZDA20105 SPORT, 2.3 L, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 550 (ON-BOARD DIAGNOSTIC [ENGINE CONTROL SYSTEM L3))DTC P2251 [L3]NOTES
2010 Mazda 5 Sport, 2.3 L, Standard

DTC P2251 [L3]: Notes

2010 Mazda 5 Sport, 2.3 L, StandardSECTION Notes
WARNING: This page is about a different car, the 2008 Mazda 5. However, it is still accessible from the selected car via links, so may be relevant.
DTC P2251 [L3] DETECTION CONDITIONS AND POSSIBLE CAUSES

DTC P2251 Front HO2S negative current control circuit open
DETECTION CONDITION 
  • The PCM monitors front HO2S 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 front HO2S negative current control circuit is open.
    • The front HO2S 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 
  • Battery voltage: 10-18 V 

Diagnostic support note 
  • This is a continuous monitor (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 is available.
  • DTC is stored in the PCM memory
POSSIBLE CAUSE 
  • Front HO2S malfunction
  • Connector or terminal malfunction
  • Open circuit between PCM terminal 2AC and front HO2S terminal D
  • Front HO2S heater can not be controlled
  • PCM malfunction
G05542992
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.