P0135 Code: Toyota Camry (2018-2024) - Causes, Symptoms & Fixes

No recalls found in NHTSA database

1. CODE MEANING AND SEVERITY

• Code: P0135
• Description: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
• What it means on a Camry (2018–2024): The upstream oxygen sensor (Bank 1, Sensor 1) heater element is not being wired, powered, or read correctly. The heater inside the upstream O2 sensor is supposed to warm the sensor quickly to operating temperature. If the heater circuit is faulty, the sensor may not heat up properly, causing delayed response, higher emissions, and less accurate air-fuel control.
• Severity: Moderate. The catalyst and emissions can be affected if the sensor never reaches the proper operating temperature, and fuel economy can suffer. The MIL (check engine light) will typically stay on. If left unaddressed, it can lead to poor drivability in cold starts and potential catalyst issues over time. In some vehicles, a persistent P0135 can coincide with other O2 sensor or ECU faults.

2. COMMON CAUSES ON TOYOTA CAMRY

• Faulty upstream O2 sensor (Bank 1 Sensor 1) heater element has failed (open or short).
• Damaged, frayed, or corroded wiring harness for the Bank 1 Sensor 1 heater circuit.
• Loose, corroded, or unplugged O2 sensor connector or pins.
• Blown fuse or wiring issue that supplies power to the O2 sensor heater circuit.
• PCM/ECU issue or intermittent communication problem with the heater circuit control.
• Contaminated or damaged O2 sensor (physical damage, oil/fuel contamination) affecting heater circuit operation indirectly.
• Exhaust manifold heat/thermal stress causing harness damage near the sensor.
• In some cases, a faulty replacement sensor or a counterfeit part.

3. SYMPTOMS

• Check Engine Light (MIL) illuminated with P0135 stored or pending.
• Longer sensor warm-up time; delayed catalyst light-off and higher emissions on cold starts.
• Potential decrease in fuel economy.
• Possible rough idle or mild drivability concerns during cold starts, though not always present.
• In some cases, no obvious drivability symptoms aside from the MIL.

4. DIAGNOSTIC STEPS
   Note: Start with basic checks and proceed systematically. Document findings and compare against the Camry’s service manual as needed.

Step 1 – Confirm and scope the issue

• Use an OBD-II scanner to confirm P0135 is current (not historical) and check for any related codes (P0130–P0134 family, P0420/P0430, or other engine codes). Note freeze-frame data and misfire counts if available.
• Check for software/ECU updates or TSBs from Toyota for P0135 (per data given, no recalls; you may still have relevant service bulletins, but the provided data only notes recalls/TSBs if present in the data set).

Step 2 – Visual inspection

• Inspect Bank 1 Sensor 1 (upstream O2 sensor) and its wiring harness for obvious damage, loose connectors, oil/fuel contamination, or heat shield contact causing chafing.
• Check the connector pins for corrosion or bent pins; ensure secure connection.
• Inspect for exhaust leaks around the upstream sensor, as leaks can affect readings and wiring harness routing.

Step 3 – Check fuses and power supply

• Locate the O2 sensor heater power supply fuse/relay (refer to the Camry’s fuse/relay diagram). Verify the fuse is intact and the relay (if used) is functioning.
• Inspect wiring path from fuse/relay to the sensor harness for damage or short to ground/power.

Step 4 – Sensor heater circuit resistance test (sensor itself)

• With the engine off and the battery disconnected or circuits isolated, remove the upstream O2 sensor (Bank 1 Sensor 1) from the exhaust as needed.
• Measure the resistance of the heater element inside the sensor. Compare with the manufacturer’s specified range (check Toyota service data; typical heater resistances are a relatively low ohm value and should be within the sensor’s spec). If the resistance is out of spec (open circuit or drastically out of range), replace the sensor.
• Inspect the sensor for contamination (oil/fuel) or physical damage; replace if necessary.

Step 5 – Circuit continuity and ground/voltage checks

• Reconnect the sensor or use the harness side to test the heater circuit:
  • With ignition ON (engine OFF) or during the PCM’s heater enable window, measure voltage on the heater circuit pin(s) relative to a good ground. If there is no supply voltage when the PCM is enabling the heater, you likely have a wiring/fuse/PCM control issue.
  • Use a multimeter to check continuity from the sensor harness pin(s) to the PCM control pin to confirm there are no opens or shorts.
  • Check for any short to ground or short to battery within the harness.
• If you do not have the proper equipment or experience, consider substituting a known-good upstream sensor to isolate whether the issue is the sensor itself or the wiring/ECU.

Step 6 – PCM/ECU considerations

• If wiring, harness, connectors, and the sensor test show no fault, the problem might lie in the PCM’s ability to drive the heater circuit. This is less common but possible. In such cases, professional diagnostic steps (including scanning for diagnostic data related to HO2S heater control and possibly software updates or ECU reprogramming) are warranted.

Step 7 – Confirm repair and verify

• If the upstream sensor is replaced, or wiring/fuse issues are corrected, clear codes and perform a road test under various conditions (cold start, idle, light acceleration) to ensure the P0135 does not return.
• Monitor live data to confirm the upstream O2 sensor heater shows “ON/HEATER” or equivalent status and that the sensor temperature rises to expected operating range quickly.

Step 8 – Consider related codes

• If you still see emission-related codes after addressing P0135, check for related O2 sensor codes (P0130, P0131, P0132, P0133, P0134) and catalytic efficiency codes (P0420, P0422, P0430) as they can illuminate after a root cause is addressed or because readouts are affected by the upstream sensor behavior.

5. RELATED CODES

• P0130 – O2 Sensor Circuit Malfunction (Bank 1 Sensor 1 or general)
• P0131 – O2 Sensor Circuit Low (Bank 1 Sensor 1)
• P0132 – O2 Sensor Circuit High (Bank 1 Sensor 1)
• P0133 – O2 Sensor Slow Response (Bank 1 Sensor 1)
• P0134 – O2 Sensor No Activity (Bank 1 Sensor 1)
• P0135 – O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) [the focus of this guide]
• P0420 / P0430 – Catalyst Efficiency Below Threshold (can appear if upstream sensor behavior causes improper exhaust readings)
  Notes: These codes are commonly observed alongside P0135 or as a consequence of prolonged heater/sensor issues.

6. REPAIR OPTIONS AND COSTS (2025 PRICES)
   Prices vary by region and shop, but here are typical ranges to plan around. All prices are ballpark figures for parts and labor; your actual costs may differ.

• Upstream O2 Sensor (Bank 1 Sensor 1) replacement

  • Parts: $40–$200 (aftermarket sensors often $60–$120; Toyota/OEM sensors commonly $120–$260)
  • Labor: 0.5–1.0 hours (typical Camry O2 sensor location is accessible with basic tools)
  • Total: roughly $100–$350 (DIY lower end if you have tools and access)

• O2 Sensor Heater Harness or Wiring Repair

  • Parts: harness segment or connectors may be $20–$100 if replacing a short connector; full harness repair might require more material
  • Labor: 0.5–2.0 hours depending on routing and access
  • Total: approximately $100–$400 (depending on extent)

• Fuses/Relays

  • Parts: $5–$30
  • Labor: minimal if you do it yourself
  • Total: $5–$40

• PCM/ECU issues

  • Parts: $300–$1,200 (new/remeasured units; dealer remanufactured can vary)
  • Labor: 1.0–2.5 hours
  • Total: $400–$1,800 (consult a professional; this is a less common fix)

• Catalytic converter or downstream sensor concerns (if misdiagnosed)

  • Parts: $150–$900 for downstream sensors; catalysts much more
  • Labor: 1.0–3.0 hours
  • Total: varies widely; typically higher than sensor replacement

DIY considerations:

• If you’re comfortable with basic electrical work and exhaust sensor removal, you can save on labor by replacing the upstream O2 sensor yourself.
• Always use anti-seize on sensor threads (as recommended by some OEMs) and torque to specification to avoid thread damage.
• Use OEM or high-quality aftermarket sensors to ensure compatibility with the Camry’s OBD-II and ECU controls.

7. DIY vs PROFESSIONAL

• DIY advantages: Lower cost, quick turn-around for sensor replacement, you control parts quality.
• DIY cautions: Misdiagnosing the circuit can lead to replacing a good sensor; incorrect harness work can cause more faults; working near hot exhaust requires care and safety.
• Professional advantages: Thorough diagnostics with proper equipment (Toyota Techstream or equivalent), precise circuit testing, ability to verify heater control from ECU, and verification of no hidden PCM issues. Pros can also check for related emissions equipment concerns (catalyst, downstream sensors) that might arise due to extended misreadings.
• When to seek a professional: If you’re unable to access the sensor or harness safely, if heater circuit testing requires specialized equipment or ECU-based diagnostics, or if the fault persists after sensor replacement.

8. PREVENTION

• Replace upstream O2 sensors at recommended maintenance intervals (often around 60,000–100,000 miles depending on driving conditions and sensor quality). Timely replacement reduces the likelihood of heater circuit faults causing drivability issues.
• Use high-quality O2 sensors (OEM or reputable aftermarket with proper fit and heater characteristics) to ensure reliable heater operation.
• Minimize exposure of the sensor and harness to heat cycling and engine vibration; secure harnesses away from sharp edges or hot surfaces.
• Address exhaust leaks promptly; leaks near the upstream sensor can alter readings and masking proper heater operation.
• Keep fuel systems clean and use quality fuel to avoid contamination that can affect O2 sensor readings.
• If you notice frequent MILs or repeated P0135 codes, have the wiring harness and PCM checked by a qualified technician to rule out intermittent electrical issues.

Data limitations and notes

• The provided NHTSA data shows one complaint for P0442 (not P0135). No recalls were found in the NHTSA database for this Camry model in the given data. This means there isn’t a documented recall targeted at P0135 in the supplied dataset; you should still treat P0135 as a legitimate fault code that can occur due to sensor/wiring/ECU issues.
• The guidance above uses general automotive knowledge for diagnosing O2 sensor heater circuit faults and is tailored for a 2018–2024 Toyota Camry. Individual vehicle configurations (engine variant, trim level, or aftermarket parts) may affect exact procedures and part numbers.

If you’d like, I can tailor this guide to your exact Camry variant (engine code, row of sensors accessible, and your preferred diagnostic tools) and provide a concise shopping list for a DIY fix.