O2 sensor codes
O2 sensor codes are often the most troublesome and misdiagnosed Check engine light problems. It is my hope that this short oxygen sensor article will open your mind to the possibilities of other problems with the vehicle at the root cause of this code being set. Replacement of perfectly good oxygen sensors is one of the most common mistakes both seasoned auto repair mechanics and do it yourself driveway mechanics make. I am not saying that these O2 sensor codes never require the replacement of the sensor itself. If your looking for cheap O2 sensors I have some popular ones listed below! In fact on all vehicles with high mileage and original parts the sensor could very well be the problem. Most American car manufacturers recommend that the O2 be replaced at 125,000 miles.
O2 sensor codes example
Recently I was working on at 2004 Ford F150 with a 5.4 L V-8 engine. The driver's complaint was the check engine light was on. I connected my scan tool and pulled a code P0133. This code stands for oxygen sensor bank one pre catalyst response slow. I went into the data stream and confirmed that the oxygen sensor had sluggish operation. When I pulled the oxygen sensor it was partially melted. If I had just replaced the sensor and shipped the vehicle it would have been back sooner than later with the same problem. In fact the 02 codes and the melted sensor meant that the problem was a lean condition that needed to be resolved.
The vehicle's computer was trying to compensate for the lean condition by increasing the amount of fuel delivered. Unfortunately for the ruined oxygen sensor the vacuum leak was so severe that the power train control module could not compensate. Lean mixtures can cause an extremely high combustion chamber temperature and post-combustion chamber temperatures as well. In fact, if this problem was not addressed. Damage to the catalytic converter was sure to be the next thing to happen.
O2 sensor codes problem solved
The vacuum leak in this circumstance was easy to find. Upon a visual inspection of the vacuum line hoses and rubber connectors I found the problem quickly. On this vehicle, the vacuum powered brake booster connects to the intake manifold through a 90° rubber elbow. The rubber had softened and swelled causing a major vacuum leak of UN metered air. This was the cause of my O2 sensor code and led to the destruction of my bank 1 oxygen sensor. So in this case, the oxygen sensor was bad, but was not the cause of the O2 sensor codes.
The vehicle I am discussing was a County owned and operated vehicle. If the driver brought the vehicle in when the check engine light first came on an oxygen sensor would have been saved. I also asked the driver if he had been experiencing poor fuel economy. The answer was a resounding yes. But since the County was filling the fuel tank, the driver put off the repair.
This failure was not an isolated incident, and Ford decided to recall and replace this 90° rubber elbow that supplies vacuum to the brake booster. The official Ford recall campaign number is 08-S-05. The O2 sensor code does not mean it's time to replace the sensor. It means that it's time for some diagnosis and repair. If you're diagnosis leads to a replacement of an oxygen sensor that is just fine. But after you replace the oxygen sensor take a moment and verify that the repair is complete. You can monitor the data stream or perform an O2 sensor test with the very affordable Actron CP 9180 scan tool. For a full review of this scanner visit my auto scanner reviews page.
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