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Mazda B40-than P0133 and P0153 O2 Sensor Fault: Diagnosis and Fix for 1997 4.0L V6 2WD

Model: Mazda B4000 Fault Code: P0133 Posted: 2015-08-01 19:11

I'm working on a 1997 Mazda B4000 with a 4.0-liter V6 engine, 2-wheel drive, automatic transmission. The check engine light reactivated after resolving an EVAP system issue. Diagnostic scanning revealed both P0133 and P0153 trouble codes — indicating problems with the oxygen (O2) sensors in Bank 1 and Bank 2. After running a live data read for approximately 45 minutes, all three O2 sensors displayed readings of 0.000, which is abnormal and suggests sensor failure or an upstream issue. This persistent zero reading explains why I'm not seeing any sensor response changes during testing. Has anyone else experienced complete failure of multiple O2 sensors simultaneously? I suspect the problem may originate upstream — possibly a vacuum leak or electrical fault — as these conditions can cause O2 sensors to respond slowly or fail to register data. I performed a carburetor cleaner spray test around the intake system, but no noticeable changes occurred (though the engine appeared cleaner). This suggests that either the sensors are physically damaged or there's an underlying issue affecting sensor signal integrity. I'm seeking advice on how to proceed — is it possible for all three O2 sensors to fail at once? Should I inspect wiring harnesses between the Powertrain Control Module (PCM) and each sensor, including connectors and sensor bodies? Any insights would be greatly appreciated. My smog expiration date is approaching, and I absolutely cannot pass emissions testing with a check engine light on. Thanks in advance for any help or suggestions!

Related fault codes
P0133P0153
Comments (2)
Anonymous 2015-08-02 11:32

If the system remains rich even after applying carb cleaner, it's likely that there is an electrical issue — start by checking the wiring harnesses between the Powertrain Control Module (PCM) and each O2 sensor. Inspect for short circuits, open circuits, or damaged connectors at both the sensor end and the PCM side. The absence of any signal from all three sensors suggests a potential fault in the sensor circuitry itself, rather than just an upstream vacuum leak.

Anonymous 2015-08-04 13:12

Thanks for the input! I suspect my Actron CP9580 scanner isn't reading data correctly — when I attempt to view live O2 sensor values, they show 0.000 and auxiliary parameters like ST FTRM1/2 and LT FTRM1/2 read -100%, which is clearly erroneous. However, the P0133 and P0153 codes were present. I replaced the Bank 1 Sensor 1 O2 sensor — after that, P0133 cleared. When P0153 reappeared, I replaced the Bank 2 Sensor 1. Since then, all error codes have been resolved. The vehicle passed emissions testing this morning with no check engine light illuminated. No further repairs needed! Thanks again for the helpful advice.