P0135: Oxygen O2 Sensor Heater Circuit Malfunction

The oxygen sensor is a component of the exhaust system in a vehicle, where it is attached to the exhaust manifold. After the internal combustion process takes place in the engine, exhaust fumes come out of it. The oxygen sensor analyzes the exhaust fumes to determine how much of its oxygen content is unburned.

This information is transmitted from the oxygen sensor to the engine control module. From there, the module can make sure the engine generates enough power while helping to reduce carbon emissions. If the exhaust fumes don’t have enough oxygen, then your engine is getting too much fuel. This lowers fuel efficiency and increases air pollution. The engine control module will respond by restricting the amount of fuel that enters the engine. But if it detects too much oxygen in the exhaust, then more fuel is sent to the engine.

When oxygen sensors get to about 600°F, they generate voltage. As long as they stay hot, they’ll continue to function properly. But if the voltage of an oxygen sensor drops to under 400 millivolts for at least 2 minutes, then it could mean you have an oxygen sensor heater circuit malfunction in bank 2, sensor 1. If you were to run a diagnostic scan on the engine control module, it should give you trouble code P0135 to confirm this.

You’ll know when it’s time to run a diagnostic check on your vehicle because the symptoms of this problem will be more than obvious. It’ll start with the Check Engine warning light coming on, followed by a rough or idle engine and a poor fuel economy. Soon you’ll see black smoke coming out of the tailpipe until your engine dies altogether. There are only rare cases where no symptoms are experienced.

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Trouble code P0135 can get triggered for several reasons. You might have an intake air system leak, exhaust system leak, bad oxygen sensor, bad air-fuel ratio sensor, bad engine coolant temperature sensor, bad sensor wiring, outdated powertrain control module, or bad powertrain control module. An experienced mechanic will be able to determine the specific cause of the trouble code P0135 coming up on the diagnostic scanning tool screen.

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