P0135 Code: Honda Civic (2022-2024) - Causes, Symptoms & Fixes

No recalls found in NHTSA database

Note on data: The prompt data shows no owner complaints and no recalls for the 2022-2024 Honda Civic with code P0135. This guide uses general automotive knowledge to explain the fault and typical repair steps, costs, and best practices. Data limitations mean you may still encounter real-world issues not captured in the provided dataset.

CODE MEANING AND SEVERITY

• What P0135 means: P0135 is an OBD-II generic code for an O2 (oxygen) sensor heater circuit malfunction. Specifically, Bank 1 Sensor 1 (the upstream O2 sensor on the bank with the number 1 cylinder) heater circuit is not operating within expected parameters. The PCM monitors the heater current and voltage; if the heater circuit is open, shorted, or readings are out of range, the PCM sets P0135 and flags a MIL (check engine light).
• Why it matters: The upstream O2 sensor heater warms the sensor quickly to operating temperature, allowing the sensor to provide accurate readings early in the exhaust cycle. A heater fault can delay proper sensor operation, leading to inaccurate air/fuel mixture data, increased emissions, and potential failure of an emissions test. Driveability is often not immediately affected, but fuel economy and emissions can degrade if the sensor never reaches proper temperature.
• Severity level: Moderate to potentially high. Illumination of the MIL and possible long-term emissions issues mean it should be addressed, especially if the monitor could affect catalytic converter efficiency or fuel economy over time.

COMMON CAUSES ON HONDA CIVIC

• Faulty upstream O2 sensor (Bank 1 Sensor 1) itself, including a bad heater element.
• Damaged or corroded wiring harness or connector between the upstream O2 sensor and the PCM (pin corrosion, frayed insulation, loose connection).
• Damaged or blown fuse/relay that supplies power to the O2 heater circuit.
• Short to ground or short to supply within the heater circuit (pinched wires, water intrusion).
• Contaminants or degraded sensor from oil/fuel blow-by that affect the sensor’s heater or sensor element (less common but possible).
• ECU/PCM issues (rare) or software reflash that affects sensor monitoring (still uncommon for P0135, but possible in some vehicles).

SYMPTOMS

• Check Engine Light (MIL) is on or blinking.
• More noticeable at startup or during cold engine operation when the heater is needed for quick sensor warm-up.
• Possible slight drop in fuel economy or richer/leaner readings reported by the vehicle’s computer, especially during startup.
• In some cases, no noticeable driveability symptoms; the issue may be primarily an emissions/fuel-trim concern.
• Infrequent misfire or rough idle is possible if the upstream sensor heater failure causes abnormal sensor readings when the engine is cold.

DIAGNOSTIC STEPS

A practical, step-by-step approach (start with non-destructive checks and progress to component replacement if needed):

• Confirm and document
  • Use a scan tool to confirm P0135 and note any freeze-frame data, pending codes, or other related codes (e.g., P0130, P0131, P0133, P0134, P0136, P0139, P0141).
  • Check the Engine Coolant Temperature and intake/engine conditions that might influence sensor readings.
• Visual inspection
  • Locate Bank 1 Sensor 1 upstream O2 sensor (before the catalytic converter). Inspect the wiring harness for chafing, damage, or disconnection. Inspect the sensor connector for corrosion or bent/poorly seated pins.
  • Inspect for oil or coolant leaks that could contaminate the sensor area.
• Electrical checks (with ignition off/on as applicable)
  • Check fuses/relays associated with the O2 heater circuit per the service manual for your Civic generation. Look for a blown fuse or a faulty relay that could cut power to the heater.
• Heater circuit testing (sensor-level test)
  • Disconnect the sensor harness from Bank 1 Sensor 1 and measure the heater resistance directly across the heater pins on the sensor using a digital multimeter (DMM).
  • Typical heated O2 sensors have a heater resistance in the range of roughly 5 to 40 ohms (exact value varies by sensor). If the resistance is effectively infinite (open circuit) or shows a very low or shorted value (near zero), the heater is faulty and the sensor should be replaced.
  • If heater resistance is within spec, check for voltage supply to the heater circuit when the ignition is on (back-probing the connector). Look for a ~12V supply when the PCM is commanding the heater on (engine will sometimes require a live signal from the PCM).
  • Check the heater ground path to ensure a solid ground; a high resistance or an open ground can prevent heater operation.
• Signal path verification
  • With the sensor connected, verify that the signal line (the O2 sensor output to the PCM) shows proper activity when the engine warms up. If the sensor never heats and never switches as expected, the issue is most likely the heater circuit (sensor, wiring, or power supply).
• Sensor replacement trial
  • If wiring and power checks pass but the fault persists, replacing Bank 1 Sensor 1 upstream O2 sensor is a common next step. After replacement, clear codes and re-check for reoccurrence.
• Additional considerations
  • If other codes exist (e.g., misfire, fuel trim limits, catalytic converter efficiency), address those issues in parallel as they can affect or be affected by O2 sensor readings.
  • If you have a strong suspicion of PCM fault after thorough testing, consulting a dealer or experienced shop is advisable due to potential software-related concerns.

RELATED CODES

• P0130: O2 Sensor Circuit Malfunction (Bank 1 Sensor 1) – generic baseline code related to oxygen sensor circuit issues.
• P0131: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1) – indicates a weak/low sensor signal.
• P0132: O2 Sensor Circuit High Voltage (Bank 1 Sensor 1).
• P0133: O2 Sensor Circuit Slow Response (Bank 1 Sensor 1).
• P0134: O2 Sensor No Activity (Bank 1 Sensor 1) – the sensor is not switching as expected.
• P0136: O2 Sensor Circuit Metering (Bank 1 Sensor 1) – another sensor response-related code.
• P0140: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) – downstream sensor heater issues (for reference, though not the same sensor position as P0135).
  Note: In the Civic’s OBD-II setup, Bank 1 Sensor 1 typically refers to the upstream heated O2 sensor; downstream sensor codes (Bank 1 Sensor 2) are related but separate.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by region, warranty status, and whether you use OEM or aftermarket parts. All estimates assume typical labor rates and standard labor times.

• Upstream O2 sensor (Bank 1 Sensor 1) replacement
  • Parts:
    • Aftermarket 4-wire heated upstream O2 sensor: roughly $60–$150
    • OEM Honda upstream O2 sensor: roughly $120–$320
  • Labor:
    • 0.5–1.5 hours, depending on access and vehicle configuration; typical shop rates: $90–$150/hour
  • Typical total: roughly $150–$500 (DIY parts plus professional labor if you’re having a shop do it; DIY sensor cost would be the part price only, plus necessary tools)
• Wiring harness/connector repair (if fault found in wiring)
  • Parts: connector or wiring repair materials (insulation, heat shield, splices) generally $10–$50
  • Labor: 0.5–2.0 hours depending on access and damage
  • Typical total: $50–$250
• Fuse/relay replacement (if the heater fuse/relay is found defective)
  • Parts: fuse/relay typically $5–$20
  • Labor: usually minimal; 0.25–0.75 hours
  • Typical total: $20–$100
• PCM/software-related issue (rare)
  • Parts: none; software update or reflash
  • Labor: 0.5–1.5 hours
  • Typical total: $60–$180 (dealer or specialized shop)

Tips:

• Replacing the upstream O2 sensor is the most common and straightforward fix for P0135, especially if the heater device itself is faulty or the wiring/connectors show damage.
• If you’re planning to sell or pass emissions tests, ensure the code is cleared and the monitor completes after the repair.

DIY VS PROFESSIONAL

• DIY feasibility
  • High-level: Replacing an upstream O2 sensor is a common DIY task for many homeowners with basic hand tools.
  • Tools you’ll likely need: O2 sensor socket (or universal socket with extension), breaker bar or ratchet, anti-seize on the threads (if sensor instructions permit; many OEM sensors come with anti-seize pre-applied), torque wrench for proper re-tightening, multimeter for resistance and voltage checks, fresh gloves, and possibly penetrating oil for stuck sensors.
  • Safety and precautions: Disconnect the battery when removing electrical connectors? In many cases, you can disconnect the negative battery terminal to be safe; allow the exhaust to cool before touching, as the sensor and exhaust components will be hot.
  • caveats: Some Honda models have sensors located in tight spots or near heat shielding; access can be challenging. Ensure you follow the sensor’s installation guidelines to avoid damaging threads or installing the sensor incorrectly.
• When to go pro
  • If the sensor is difficult to access, you suspect wiring issues that require diagnostic tracing, or you have repeated code reoccurrences after a replacement.
  • If you observe additional fault codes, misfires, or other drivability issues, a professional diagnostic approach can save time and prevent misdiagnosis.
  • If you lack the proper torque specs or feel uncomfortable with electrical diagnostics, a professional shop is recommended.

PREVENTION

• Regular maintenance
  • Use quality fuel and maintain a clean intake system to avoid contaminants affecting O2 sensor operation.
  • Address vacuum leaks, intake leaks, or exhaust leaks promptly; these can skew O2 sensor readings and affect subsequent diagnoses.
• Protect oxygen sensors
  • Avoid oil or fuel additives that could contaminate sensors; use OEM-recommended lubes/cleaners.
  • Handle sensors with care during maintenance; unplugging sensors without proper procedure can damage connectors.
• Proper installation
  • Use the correct sensor type (upstream Bank 1 Sensor 1) and ensure connectors are clean and fully seated.
  • Do not overtighten sensors; use the manufacturer’s torque spec to avoid thread damage or sensor body fracture.
• Electrical protection
  • Check wiring harness protection; ensure harnesses are routed away from heat sources, moving parts and exhaust components; use protective loom if necessary.
  • Inspect connectors for corrosion and repair any damaged pins or seals promptly.

If you’d like, I can tailor a step-by-step home diagnostic flow for your exact Civic trim (engine size, generation) or provide a printable checklist you can bring to a shop.