Engine Light ON (or Service Engine Soon Warning Light),Possible higher than usual fuel Consumption
P0135 CHEVROLET Possible Causes
Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1,Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse,Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit open shorted to ground,Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit poor electrical connection,Faulty Powertrain Control Module (PCM)
P0135 CHEVROLET Description
The Powertrain Control Module (PCM) supplies a bias voltage (approximately 450 mV) on the Heated Oxygen Sensor (HO2S) signal high and low circuits. When you turn the ignition to the ON position, battery voltage is supplied to the HO2S heater. As the heater reaches the operating temperature, the HO2S voltage responds by changing from a bias voltage range to the normal operation. Typically, as the HO2S reaches the operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, it is possible for the HO2S voltage to go above 450 mV. The PCM runs the heater test only on a cold start (depends on the cumulative air flow) and only once an ignition cycle. When you start the engine the PCM monitors the HO2S voltage. When the HO2S voltage goes above or below the bias range threshold, the PCM determines how much time it took.
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