P0135 GMC Sierra 1500
O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1) · Powertrain Code · Low · Repair: Moderate
What is P0135?
The heater circuit in the upstream O2 sensor on bank 1 has failed, delaying sensor warm-up.
When the GMC Sierra 1500 triggers code P0135 (o2 sensor heater circuit malfunction (bank 1, sensor 1)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the GMC Sierra 1500.
This repair is rated moderate, meaning some experience and specialty tools required.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your GMC Sierra 1500.
Common Causes on GMC Sierra 1500
- Failed O2 sensor heater element in Bank 1 Sensor 1
- Blown fuse in the O2 sensor heater circuit
- Corroded or damaged wiring to the O2 sensor heater
- PCM driver circuit fault (rare)
Symptoms
- Check Engine Light on
- Extended warm-up period for closed-loop fuel control
- Slightly higher emissions during cold start
- May fail emissions inspection
Notes for GMC Sierra 1500
GM O2 sensor connectors are often heat-damaged on V8 trucks due to proximity to exhaust manifolds — inspect the connector before assuming the sensor itself has failed.