Rick's Free Auto Repair Advice

P0135 O2 Sensor Heater Circuit Malfunction

Fix code P0135

P0135 Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1). This sensor is located on the engine bank that houses #1 cylinder and is located BEFORE the catalytic converter

When you turn the ignition switch to RUN, the vehicle provides to the heater circuit of the oxygen sensor. The oxygen sensor heater is a critical part of the vehicle’s emission system because it brings the oxygen sensor up to operating temperature much faster than from the heat of the exhaust alone.

Oxygen sensor heater receives ground from the PCM

The heater completes the circuit by receiving ground from the PCM. That’s done on purpose so the PCM can monitor voltage on the ground side to determine whether the heater is operating properly. When the heater is running properly, the PCM expects to see a large voltage drop and low current on the ground connection. However, if there’s a problem on the power supply side, in the heater itself or corrosion in the connector or wiring, the PCM will see a higher than expected voltage or current on the ground. The test fails when current draw exceeds a programmed limit and/or an open or short is detected.

Causes of P0135

Most common causes are: Pinched, open, shorted, and corroded wiring and pins. Crossed sensor wires. Contaminated or damaged sensor. Blown fuse, open or short to ground, dead heater in sensor, bad ground wire between sensor and PCM.

oxygen sensor, P0130


To learn how to replace an oxygen sensor, click here


© 2012 Rick Muscoplat


Posted on by Rick Muscoplat

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