P0135 – O2 Sensor Heater Circuit (Bank 1 Sensor 1)

Description

The ECM detects a malfunction in the heater circuit of the upstream O2 sensor on Bank 1.

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Symptoms

Poor fuel economy
Rough idle
Extended time to closed loop
Check engine light

Causes

Failed heater element in O2 sensor
Blown fuse
Open or shorted wiring
Poor electrical connection

Diagnosis

Check O2 heater fuse and power feed
Measure heater resistance with multimeter
Backprobe heater power and ground
Inspect wiring and connector for damage

Repair

Replace O2 sensor if heater is open or shorted
Repair or replace damaged wiring
Replace blown fuse after fixing root cause