P0135 on the 2022 Honda Civic
The 2022 Honda Civic launched the 11th generation on the Honda platform with the 2.0L K20C2 (158 hp) or 1.5L turbocharged L15CA (180 hp). The P0135 code means the ECM has detected a problem with the upstream O2 sensor's internal heater circuit. This heater is critical for cold-start emissions reduction, as it brings the sensor to operating temperature within seconds of engine startup.
Understanding the O2 Sensor Heater
The upstream O2 sensor on the Civic contains two separate systems: the sensing element that reads exhaust oxygen, and a heater element that warms the sensor quickly. The P0135 code specifically addresses the heater side. When the heater fails, the sensor still works once it warms up from exhaust heat, but that process takes 2-5 minutes instead of 20-30 seconds, during which time the engine runs in pollutant-producing open-loop mode.
Why the Heater Fails
- Heater element burnout: The most common cause in Honda Civics. The internal resistance wire that generates heat gradually degrades from thermal cycling. Each start-stop cycle stresses the element, and after thousands of cycles, it eventually fails. This is particularly common on Civics used for short-trip commuting.
- Blown heater circuit fuse: A quick check that many owners miss. The underhood fuse box contains a dedicated fuse for the O2 sensor heater circuit. If this fuse is blown, the heater cannot function.
- Connector or wiring fault: The heater circuit runs from the ECM through the fuse box to the sensor connector. Corrosion at the connector, frayed wiring near the exhaust, or a pinched wire in the harness can interrupt the circuit.
- ECM driver circuit: Rarely, the transistor inside the ECM that switches the heater power on and off can fail. This is diagnosed by exclusion after verifying the sensor, fuse, and wiring are all functional.
Symptoms You Will Notice
The check engine light is the most prominent symptom. The 2022 Civic may idle slightly rougher for the first minute or two after a cold start. Fuel economy on short trips may decrease because the engine stays in rich open-loop mode longer. Once the engine and sensor warm up, drivability returns to normal. Many Civic owners report driving for weeks with P0135 before noticing any performance change.
Step-by-Step Diagnosis
- Locate and test the O2 sensor heater fuse in the underhood fuse box. If blown, replace and monitor for recurrence.
- With the sensor connector disconnected, measure the heater circuit resistance with a multimeter. The reading should be 2-15 ohms. An open circuit confirms heater element failure.
- Check for 12V at the heater power pin with key on. No voltage means the issue is upstream of the sensor.
- Inspect the connector for corrosion, melted plastic, or bent pins.
- If sensor, fuse, and wiring all check out, suspect the ECM driver circuit.
Costs
OEM Denso O2 sensor: $80-$165. Aftermarket (Bosch, NGK): $40-$80. Dealer labor: $100-$180. Total dealer repair: $180-$345. Fuse: under $10. Wiring repair: $100-$250. Honda dealer labor: $120-$165/hour.
DIY Rating
This is an easy DIY repair on the 2022 Civic. The upstream sensor is accessible from above on both engine options. Start by checking the fuse (free), then use a 22mm O2 sensor socket if a sensor replacement is needed. The entire process takes 20-40 minutes including diagnosis.