What is the P0135 fault code?
2 Answers
P0135 fault code refers to a malfunction in the heating circuit of the first oxygen sensor in group one. This code will appear if the current consumption exceeds the calibrated limit or if an open or short circuit is detected. Possible causes include a faulty oxygen sensor heater circuit connector, a defective oxygen sensor itself, or an issue with the electronic control module. The sensitive element in the oxygen sensor that generates voltage signals is made of zirconium dioxide, with a layer of platinum on its outer surface and a ceramic layer protecting the platinum electrode. The inner side of the sensitive element is exposed to the atmosphere, while the outer side is in contact with engine exhaust gases. If the oxygen sensor fails to output a signal or outputs an abnormal signal, it can lead to increased engine fuel consumption and exhaust pollution, resulting in symptoms such as unstable idle, misfires, and engine shuddering.
Hey, I've come across the P0135 trouble code several times, especially when driving older cars. Simply put, it tells you there's an issue with the front oxygen sensor's heating circuit. This sensor is located at the front of the engine and is responsible for monitoring the air-fuel mixture ratio to help the car achieve better fuel efficiency and cleaner emissions. If the heating element fails, the sensor can't warm up quickly enough to function properly—this is especially noticeable in winter when the check engine light comes on, and the car may feel sluggish with skyrocketing fuel consumption. The main causes are aging wiring causing a short circuit, a burnt-out sensor itself, or sometimes a blown fuse. I've chatted about this while working on cars in the neighborhood garage, and many friends have encountered similar issues. It's not too complicated to fix, but don't delay—early inspection can prevent damage to the engine and catalytic converter, which would otherwise lead to higher repair costs. Safety first; don't let small issues escalate. I recommend first checking the sensor connector and fuse box. If that doesn't solve it, take it to a repair shop.
