P0135 Code: Honda CR-V (2017-2023) - Causes, Symptoms & Fixes

Diagnostic guide: P0135 on 2017-2023 Honda CR-V

Summary of recall data (per the provided dataset)

• No recalls found in NHTSA database for 2017-2023 Honda CR-V related to P0135.
• No NHTSA owner complaints reported for this exact make/model/year/issue combination in the provided data.
• Note: P0135 is a common OBD-II DTC across many vehicles. This guide uses general knowledge for diagnosis and repair, while acknowledging the dataset limitations above.

CODE MEANING AND SEVERITY

• Code: P0135
• Full definition: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
• What it means:
  • Bank 1 Sensor 1 is the upstream (pre-catalytic converter) oxygen sensor on the primary exhaust bank.
  • The heater circuit inside that sensor is not functioning as expected. The heater helps bring the sensor to operating temperature quickly for accurate readings.
• Why it matters:
  • A non-functioning heater can delay heater warm-up, delaying catalyst light-off, increasing emissions, and potentially triggering the MIL (Check Engine Light).
  • In many cases, you’ll see reduced fuel economy or the PCM using less accurate oxygen readings while the sensor “heats up” slowly.
• Severity:
  • Moderate. It is primarily an emissions/monitoring issue. If left unresolved, it can lead to higher emissions, possible catalyst heating delay, and in some cases downstream oxygen sensors or catalyst-related codes may appear later. Drive-ability is usually not immediately affected, but some drivers notice rough idle or hesitation only if other related issues exist.

COMMON CAUSES ON HONDA CR-V

• Upstream O2 sensor (Bank 1 Sensor 1) heater element failure or internal short/open circuit.
• Damaged or corroded wiring between the upstream O2 sensor and the PCM (insulation wear, rubbing, or broken pins).
• Loose, damaged, or dirty sensor connectors; poor ground path on the sensor harness.
• Blown fuse or relay that supplies power to the O2 sensor heater circuit.
• Short to ground or short to power in the sensor harness or at the connector.
• Exhaust/thermal environment causing wire insulation damage near the manifold.
• PCM/ECU fault or intermittent control signal (less common but possible).
• Water intrusion or contamination in the sensor harness or connector.
• Aftermarket modifications or aftermarket sensors that don’t meet OEM heater specs.

Notes specific to CR-Vs (2017-2023):

• Upstream Bank 1 Sensor 1 on these engines (regardless of turbo vs naturally aspirated variants) is the usual source for P0135. Ensure you’re testing the correct sensor and its two heater leads, not downstream sensors.
• In some CR-Vs, the O2 sensor heater circuit is controlled/monitored by the PCM; a failure can be intermittent if wiring or connector tension changes with engine heat cycles.

SYMPTOMS

• Illumination of the Check Engine Light (MIL) on the dash.
• Often no noticeable driveability issue (idling, acceleration, and cruising feel may be unaffected if the downstream sensor and fuel control are otherwise healthy).
• Possible mild decrease in fuel economy due to longer fuel trims or improper catalyst warm-up behavior.
• In some cases, you may see related codes after driving (e.g., P0130-P0134 family or P0420 for catalyst efficiency) if the system runs lean/rich or the catalyst heats slowly.
• If the upstream sensor’s heater is completely failed and fault is persistent, you’ll see the MIL stay on until the fault is repaired and codes cleared.

DIAGNOSTIC STEPS

Important: Start with a proper scan to confirm P0135 is current. Note freeze-frame data and any other codes present.

A. Initial verification

• Use an OBD-II scanner to confirm:
  • Code: P0135 (Bank 1 Sensor 1 Heater Circuit Malfunction)
  • Any related codes (P0130-P0134, P0135, P0136, P0138, P0139, P0420, etc.)
• Check readiness monitors and drive cycle status if possible.

B. Visual inspection

• Inspect the upstream O2 sensor (Bank 1 Sensor 1) and its connector for:
  • Corrosion, oil/fuel contamination, or exhaust heat damage.
  • Broken or frayed wires, especially near the connector or where the harness runs along the exhaust manifold.
  • Loose or bent pins in the connector.
• Check for any obvious exhaust leaks near the upstream sensor, which could affect readings and heated operation.

C. Electrical checks (diagnostic approach)

• Fuse/relay check:
  • Locate the O2 sensor heater power circuit fuses/relays per the service manual and verify they’re intact.
  • Replace any blown fuse or faulty relay as required.
• Wiring harness check:
  • Inspect the heater circuit wiring for short to ground, short to power, or open circuits.
  • Look for pin push-out or loose ground connections at the PCM side.
• Sensor heater circuit test (when the engine is cold):
  • Disconnect the O2 sensor connector (Bank 1 Sensor 1) and measure the sensor heater resistance across the heater pins with a multimeter.
  • Compare the measured resistance to the OEM specification for Bank 1 Sensor 1. If resistance is out of range or infinite (open circuit), the sensor is likely faulty and should be replaced.
  • Reconnect the sensor and perform a live-diagnosis with an OBD-II scanner:
    • While the engine is warming up, observe the O2 sensor live data for Bank 1 Sensor 1.
    • Check whether the PCM is actively energizing the heater (look for a heater duty cycle or a 12V signal on the heater circuit when the engine is cold). If the heater signal is not present when cold, or remains off for a long period, there’s likely an issue in the heater circuit (sensor, wiring, or PCM control).
• Functional swap test (if feasible and you have a known-good sensor):
  • Swap in a known-good upstream O2 sensor (Bank 1 Sensor 1) and clear codes.
  • If P0135 reappears with the new sensor, the issue is likely in wiring, fuse/relay, or PCM control.
  • If the code clears and does not return after a drive, the old sensor was defective.

D. Additional consideration

• If the upstream sensor tests pass (resistance is in range, heater signal present when commanded, no wiring fault found) but the code persists, consider PCM/control-path issues or a rare intermittent connection. In such cases, professional diagnostics may be needed, including service manual references and wiring diagrams.

E. Test-drive after repair

• Clear codes and perform a short drive to ensure the MIL does not return.
• Re-check for any new codes after a complete drive cycle.
• Confirm that catalytic converter and O2 sensor monitoring are functioning through readiness checks.

RELATED CODES

• P0130: O2 Sensor Circuit (Bank 1 Sensor 1) Malfunction (often a broad O2 sensor issue family)
• P0131: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
• P0132: O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
• P0133: O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
• P0134: O2 Sensor Circuit No Activity (Bank 1 Sensor 1)
• P0136: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) [note: different sensor, but heater-related family)
• P0420: Catalyst System Efficiency Below Threshold (can appear if catalyst warm-up is delayed or if sensor readings lead to poor catalyst performance)
• P0135 is specifically the bank-1 upstream heater fault; if you see any of the above, they may share the same upstream sensor path or indicate related sensor misbehavior.

REPAIR OPTIONS AND COSTS (2025 prices)

Important: Actual prices vary by region, labor rate, OEM vs aftermarket parts, and whether you perform DIY or use a dealership.

• Upstream O2 sensor (Bank 1 Sensor 1) replacement
  • Aftermarket sensor (quality brand): Part roughly $20–$100. OEM-equivalent sensors typically range $80–$180.
  • Labor: About 0.5–1.5 hours (depending on access, model variant, and whether components need removal to reach the sensor).
  • Typical total (parts + labor): $120–$300 (aftermarket) or $180–$430 (OEM).
• Wiring harness or connector repair
  • If wiring is damaged, you may only need a harness repair or a connector replacement.
  • Parts: $10–$60 for a connector or small harness segment.
  • Labor: 0.5–1.0 hour.
  • Typical total: $60–$180.
• Fuses/relays
  • Minor cost if a fuse/relay is the culprit.
  • Parts: $5–$30.
  • Labor: Minimal (often DIY-friendly).
• PCM/ECU issue (rare)
  • If a PCM fault is suspected after exhaustively ruling out sensor and wiring, replacement or reprogramming can be costly.
  • Parts: Several hundred to over a thousand dollars (including programming).
  • Labor: Several hours.
• DIY vs professional
  • DIY: Replacing the upstream O2 sensor yourself can save on labor costs; ensure you have the correct sensor type for Bank 1 Sensor 1 and follow safe exhaust-tap procedures.
  • Professional: Recommended if you’re not comfortable testing electrical circuits or accessing the sensor, or if a fault isn’t easily diagnosed.

DIY VS PROFESSIONAL

• DIY considerations:
  • Suitable if you’re comfortable with basic electrical testing, using a multimeter, and following service manual procedures.
  • Pros: Lower cost, faster turnaround if you have parts in hand.
  • Cons: Risk of misdiagnosis if you don’t verify wiring, fuses, and sensor performance; potential to misinterpret live data.
• Professional considerations:
  • Pros: Access to manufacturer service data, wiring diagrams, and advanced diagnostic tools (scope, bi-directional control tests).
  • Cons: Higher labor cost; potential wait times depending on shop.

PREVENTION

• Use high-quality oxygen sensors and avoid short-life aftermarket sensors that don’t meet OEM specs, especially for the heated upstream sensor.
• Inspect wiring harnesses around the exhaust manifold and engine area regularly; look for signs of heat damage, chafing, or moisture intrusion.
• Keep electrical connections clean and dry; use dielectric grease on connectors during reinstall to resist corrosion.
• Address exhaust leaks promptly; a leak near the upstream sensor can cause erroneous readings and stress the heater circuit.
• Follow service intervals for O2 sensors per Honda spec or owner’s manual; replace upstream sensors at recommended intervals or sooner if readings become erratic.
• Ensure proper engine maintenance (spark plugs, fuel system cleaning, air intake) to minimize unnecessary sensor stress and erroneous fuel trims.
• Avoid excessive humidity or water ingestion into connectors when working under the hood; cover connectors if performing water exposures.

Data limitations and transparency

• The provided dataset indicates no recalls and no NHTSA complaints for this exact combination (Honda CR-V 2017-2023 with P0135). This guide uses general automotive knowledge and typical diagnostic practices for P0135 across modern Honda engines. Individual vehicles may vary, and always verify with OEM service information for exact wiring diagrams, fuse/relay locations, and sensor specifications.
• If you’re considering major repairs or replacement, verify current pricing locally, since 2025 prices can vary substantially by region and shop.