2004 Mazda 3s, 2.3L

I’ve been getting CEL P2178 and P2188. Essentially, I’m running rich on and off idle.
So far, I’ve cleaned the throttle body, and MAF sensor.
Replaced spark plugs, purge valve, and air filter.
I’ve checked for degradation of MAF and front O2 sensor wires but found nothing.
I’ve also recently checked for vacuum leaks but didn’t find any.

Aside from the running rich codes, I got P2196 (I think) it was the the O2 sensor was stuck open, this was right after I replaced the purge though then cleared itself and hasn’t returned.

The only other symptoms I’ve had are at idle some sputtering and changes in RPM, this only happens when in drive though. If I shift to neutral it immediately stops. It also only occurs when the engine is warm and has been put under a bit of stress.

If you have any suggestions as to what to do next that’d be great.


1 thought on “2004 Mazda 3s, 2.3L”

  1. You can read the technical information below, but in short I would recommend replacing the upstream O2Sensor.

    P2188 Mazda – System Too Rich At Idle Bank 1

    Possible causes
    – Leaking fuel injector or pressure regulator
    – High fuel pressure condition
    – Faulty Oxygen (O2) Sensor
    – Faulty Mass Air Flow (MAF) sensor

    P2196 Mazda – O2 Sensor Signal Stuck Rich Bank 1 Sensor 1
    Possible causes
    – Faulty Front Heated Oxygen Sensor Bank 1
    – Front Heated Oxygen Sensor Bank 1 harness is open or shorted
    – Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
    – Inappropriate fuel pressure
    – Faulty fuel injectors
    – Intake air leaks may be faulty
    – Vacuums leaks

    The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

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