What does code P0135 mean on a GMC and is it safe to drive?

P0135: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1). Here’s what it means on your GMC, what usually causes it, what repairs typically cost, and how safe it is to keep driving.

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What this code means

The heater circuit for the upstream O2 sensor on bank 1 has a fault. Sensor may still work but take longer to go closed-loop.

Common causes for your GMC

Failed O2 sensor (heater element)
Open or short in heater wiring

Symptoms

Check Engine Light
Possible slightly worse fuel economy

Typical fixes

Replace bank 1 sensor 1 O2 sensor
Repair wiring

Repair cost range

For a GMC, repairs for P0135 often fall between $80 and $300, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.