P0155 Code: Toyota Camry (2018-2024) - Causes, Symptoms & Fixes

Below is a comprehensive diagnostic guide for P0155 on a 2018–2024 Toyota Camry. Note on data: the provided NHTSA data set includes one complaint for a different code (P0442) and lists no recalls for this make/model. No recalls are shown in the data. This guide uses general, model-relevant knowledge for P0155 and Camry 2018–2024, plus typical repair cost ranges in 2025. Data limitations: P0155-specific complaint counts are not present in the supplied data, so statistical trends are not drawn from that dataset.

CODE MEANING AND SEVERITY

• Code: P0155
• Full description (general): O2 Sensor Heater Circuit Malfunction — Bank 2 Sensor 1
  • Bank 2 Sensor 1 is the upstream oxygen sensor on the second bank. The heater within that sensor is not heating as expected, causing slow or insufficient heating of the sensor.
• Why it matters:
  • Oxygen sensors rely on heat to reach their operating temperature quickly. When the heater circuit is faulty, the sensor runs cold longer, producing inaccurate readings. The engine control module (ECM) may run open-loop longer, affecting fuel trim, emissions, and catalyst efficiency.
• Severity and symptoms:
  • Moderate severity. It often sets MIL (check engine light) and can impact fuel economy and emissions performance. Some Camrys may run roughly or feel slightly off during cold starts or light-load operation, but drivability is usually not catastrophic.
  • In some cases, the vehicle may still drive normally once the sensor heats up, but the fault can persist and store codes until corrected.

COMMON CAUSES ON TOYOTA CAMRY (2018–2024)

• Faulty Bank 2 Sensor 1 oxygen sensor (the sensor’s heater element has failed).
• Damaged or corroded harness or connector to Bank 2 Sensor 1 (insulation wear, exposed conductor, bent/pinossa).
• Faulty power supply or grounding for the O2 heater circuit (fuse or ground path issue).
• Blown fuse or relay feeding the O2 sensor heater circuit.
• Electrical short to ground or to a power source in the heater circuit.
• Wiring harness routing contact with hot exhaust components causing insulation damage.
• ECM/PCM fault affecting heater drive signals (less common).
• Aftermarket wiring/edits or use of non-OE sensors with different heater specifications.
• Exhaust leaks near the sensor can indirectly affect readings, though the heater fault itself is electrical.

SYMPTOMS

• Check Engine Light (MIL) illuminated with P0155 stored or pending.
• Increased fuel trims during cold-start or when the sensor remains cold.
• Possible slight decrease in fuel economy; more noticeable emissions during cold starts.
• Infrequent or no noticeable drivability issues; the car may run normally once the sensor heats and the engine enters closed-loop.
• No immediate stored misfire codes unless other faults accompany it.

DIAGNOSTIC STEPS (step-by-step approach)

Important: Begin with the simplest, least invasive checks and move toward more invasive tests as needed.

• Step 1: Confirm code and freeze data

  • Use a capable OBD-II scanner to confirm P0155 (Bank 2 Sensor 1 Heater Circuit Malfunction) and review freeze frame data (engine coolant temp, fuel trims, engine speed, etc.) for context.

• Step 2: Visual inspection

  • Inspect the Bank 2 Sensor 1 (upstream O2 sensor) and its wiring harness and connector for damage, oil/contaminant exposure, corrosion, or missing/loose pins.
  • Check for signs of exhaust heat damage, chafing, or harness contact with sharp edges or hot surfaces.
  • Inspect the fender/engine bay area for damaged insulation and any signs of past repairs.

• Step 3: Electrical power supply and ground

  • Locate the O2 heater power supply fuse(s) and relay(s) in the fuse/relay box. Verify the fuse is intact and that power is present at the heater circuit when the ignition is on.
  • With the sensor disconnected (careful to avoid shorting), check heater circuit resistance with a multimeter (between the heater wires). Compare to the manufacturer’s spec for Bank 2 Sensor 1 (consult service data for exact resistance; typical heater resistance is in a low-ohm range, often 2–12 Ω depending on sensor type).
  • Check for proper ground return for the heater circuit.

• Step 4: Heater activity verification (engine running or key-on)

  • Using a scan tool with an “O2 sensor heater test” or live data, verify whether the ECM is commanding the Bank 2 Sensor 1 heater to turn on and whether current flows through the heater.
  • If the heater is not being commanded on despite a good power supply and ground, the sensor or PCM may be at fault.
  • If the heater is commanded on but current is very low or absent, suspect a bad sensor or wiring issue.

• Step 5: Sensor integrity check

  • Inspect the Bank 2 Sensor 1 sensor body for contamination, visible damage, or signs of overheating.
  • If the sensor is old or heavily contaminated, replacement is often the practical fix.

• Step 6: Wiring harness tests (if power and ground look good)

  • Perform continuity checks along the harness from the connector to the ECM/PCM, looking for opens, shorts, or high resistance.
  • Check for cross-connections or pin deformation in the connector that could cause intermittent contact.

• Step 7: Component swap/test (if available)

  • If you have a known-good Bank 2 Sensor 1, swap it temporarily to determine if the fault code clears. If the code clears, the sensor was the culprit.
  • If no spare sensor is available, you may opt to replace Bank 2 Sensor 1 with an OEM or reputable aftermarket unit and re-test.

• Step 8: Re-test and verify

  • After any repair (sensor replacement, wiring repair, fuse replacement), clear codes and perform a road test under varying conditions to ensure the code does not return and that the sensor heater warms properly (verify with live data once the engine has warmed).

Notes:

• Bank 2 Sensor 1 is upstream; heater issues can worsen cold-start emissions, so expect normalization only after the sensor heats.
• If multiple heater circuit faults appear (P01xx family), ensure you’ve checked for common power/ground issues and fuses first before swapping sensors.
• Exhaust leaks or catalytic converter issues can complicate O2 readings, but they do not directly cause a heater circuit fault.

RELATED CODES

• O2 sensor heater/circuit family often includes:
  • P0135, P0136, P0137 (Bank 1 sensors, heater circuits)
  • P0141, P0142, P0145 (Bank 1/Bank 2 downstream heater circuits)
  • P0150, P0151, P0154, P0155 (Bank 2 Sensor 1 and related positions)
• Other related fuel/air sensor and circuit codes may appear if the ECM shifts to open-loop or mass air flow readings are affected.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by region, shop, and whether OEM or aftermarket parts are used. The ranges below reflect typical U.S. pricing in 2025.

• Bank 2 Sensor 1 O2 sensor replacement (most common fix)

  • Parts: Aftermarket sensor roughly $50–$150; OEM sensor typically $120–$350.
  • Labor: Approximately 0.5–1.5 hours (some Camry models are easier or harder depending on access).
  • Typical total: $180–$450 (aftermarket sensor) or $350–$700 (OEM sensor at dealer).

• Wiring harness/connector repair

  • Parts: Minimal (connector repair or pin replacement may be included with the harness). If a harness segment is replaced, parts might run $20–$100.
  • Labor: 1–2 hours.
  • Typical total: $120–$350, depending on extent of repair and whether wiring damage is localized or extensive.

• Fuse/relay replacement

  • Parts: $5–$15.
  • Labor: Minimal (often a DIY task or a quick shop inspection).
  • Typical total: $10–$40.

• ECM/PCM fault (rare)

  • Parts: ECM replacement is expensive and uncommon for this fault.
  • Labor: 1–2 hours plus programming; total could be $400–$1200 depending on dealer vs. independent shop.

• Summary guidance

  • The most cost-effective fix, when the sensor is determined to be faulty and wiring is sound, is replacing Bank 2 Sensor 1 with a quality sensor.
  • If wiring or fuses are at fault, costs drop significantly but can be time-consuming to diagnose.

DIY VS PROFESSIONAL

• DIY considerations (cautious, capable DIY)

  • Pros: Lower cost, learning opportunity, sensor replacement is a common DIY task.
  • Cons: Electrical diagnosing without a proper scan tool can be challenging; misdiagnosis can lead to recurring codes.
  • Tools you’ll likely need: OBD-II scanner with live data, multimeter, backprobe/module wiring harness tools, basic hand tools, safety gear for exhaust work, and anti-seize compound for reassembly if needed (some sensors use anti-seize on threads; verify manufacturer recommendation).
  • Steps you can reasonably perform yourself: Visual inspection, fuse/relay check, simple resistance checks on the sensor (if you have the spec), and sensor replacement.

• Professional repair considerations

  • Pros: Access to OEM/service data, precise heater circuit testing, proper electrical diagnostics, and correct torque specs for sensor installation.
  • Typical workflow: Confirm code, inspect wiring/fuses, test heater command and ground, use live data to verify sensor heating, replace sensor or repair wiring, clear codes, road test, re-check for reoccurrence.

• Safety notes

  • Work around the exhaust system can be dangerous when hot. Always let the exhaust cool.
  • Disconnect the battery only when necessary and follow proper anti-static precautions when handling electronic connectors.
  • When removing or installing sensors, avoid cross-threading and apply the appropriate thread compound if recommended by Toyota.

PREVENTION

• Regular maintenance and good fuel quality help reduce sensor contamination and heater circuit stress.
• Address exhaust leaks promptly, as leaks can influence O2 sensor readings and catalytic converter efficiency.
• Inspect O2 sensor wiring during routine service, especially if the vehicle has high mileage or has experienced heat exposure near the sensor.
• Use OEM or high-quality sensors certified for your Camry model to ensure proper heater resistance and electrical compatibility.
• Keep connectors clean and dry; apply dielectric grease to connectors only as recommended by the vehicle manufacturer to avoid loosening or corrosion.
• If you replace a sensor, ensure the wiring harness is secured away from hot surfaces and sharp edges to prevent future wear.

Data limitations and closing notes

• The provided data set for NHTSA contains no P0155 entries, and no recalls are listed for the Camry 2018–2024 in that data. This guide uses general OBD-II and Toyota Camry sensing knowledge for P0155, plus typical 2025 cost expectations. Real-world results may vary by vehicle condition, maintenance history, and region.