P0155 Code: Chevrolet Malibu (2017-2023) - Causes, Symptoms & Fixes

Here is a comprehensive diagnostic guide for OBD-II code P0155 on 2017–2023 Chevrolet Malibu. Note the data available from NHTSA in your prompt: no recalls for this model/year were found, and only two owner complaints exist in the dataset (P0302 and P0420). No direct P0155 entries are in that data, so this guide uses general OBD-II knowledge augmented with Malibu-specific considerations and the data limitations you provided.

CODE MEANING AND SEVERITY

• What P0155 means: P0155 is OBD-II Trouble Code P0155 — O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1). In plain terms, the heater element inside the Bank 2 upstream O2 sensor is not heating properly or the heater circuit is not functioning. The heater helps the sensor reach its operating temperature quickly for accurate readings; a faulty heater can cause slow sensor response, degraded catalyst efficiency readings, and higher emissions until the sensor heats up normally.
• Severity: Moderate. If the heater circuit is truly open/failed, the PCM may rely on the sensor’s unheated reading, which can cause longer warm-up periods for the sensor and possible emission-related drivability concerns. In many inline-4 Malibu engines, Bank 2 may not be present in the traditional sense (see Malibu-specific notes below), so confirm sensor location with the service data. A persistent P0155 can lead to elevated emissions and potentially trigger the MIL, but driveability issues often depend on other codes (e.g., related O2 sensors, fuel trims, or catalyst condition).
• Data limitations: The provided NHTSA data for Malibu (2017–2023) does not include a P0155 case and shows no recalls. The guide below uses standard diagnostic logic for P0155 and adds Malibu-specific considerations.

Malibu-specific note on banks/sensors:

• Malibu engines in this era (1.5 L turbo / 2.0 L turbo; inline-4 designs) are typically configured with Bank 1 sensors (and Bank 2 sensors if the engine family has more than one bank). Some inline-4 setups effectively have a single bank, and the P0155 label (Bank 2 Sensor 1) may be less common or mislabeling can occur. If you see P0155 on a Malibu, verify the actual sensor location with the OEM/repair manual or scan tool’s live data (it may report “S1” on a sensor that acts as Bank 2 in the vehicle’s bank mapping). This can avoid chasing a non-existent Bank 2 heater circuit.

COMMON CAUSES ON CHEVROLET MALIBU

• Damaged, corroded, or unplugged O2 sensor heater wiring or connector (Bank 2 Sensor 1 or its equivalent in Malibu’s bank mapping)
• Open/short in the heater circuit wiring (broken wire, pin misalignment, damaged insulation, harness chafing near the exhaust)
• Blown fuse or relay supplying power to the O2 heater circuit
• Faulty O2 sensor (the heater element itself has failed)
• Poor or intermittent grounds on the sensor or PCM side
• PCM/ECM fault or software issue affecting heater power control
• Misidentification by scan tool: ensure you’re looking at the correct sensor location for your vehicle; some Malibu configurations may show P0155 due to labeling differences

SYMPTOMS

• MIL (Check Engine Light) on or flashing
• Emissions test may fail or show elevated emissions
• Slightly degraded fuel economy or less precise fuel trims until the sensor heats
• In some cases, no obvious driveability issue (sensor is slow to heat; performance seems normal once at operating temp)
• In Malibu, if P0155 coincides with other O2 codes, you may notice hesitation or rough idle depending on the interaction with other sensor readings

DIAGNOSTIC STEPS

Note: Some steps assume you have basic automotive tools and a capable OBD-II scan tool. If you’re not comfortable with electrical testing, skip to the “DIY vs PROFESSIONAL” section.

A. Verify the code and sensor location

• Use a capable OBD-II scanner to read live sensor data and identify which sensor is flagged as the heater circuit fault.
• Check for related codes (e.g., P0135, P0136, P0137, P0141, P0150–P0154, P0138, P0155’s companion codes). If you only have P0155, confirm the sensor’s actual location on your Malibu (Bank 2 Sensor 1 vs. Bank 1 Sensor 1 ambiguity).
• Look at freeze-frame data to see the engine load, RPM, coolant temp, etc., at the time the code set.

B. Visual inspection

• Inspect the O2 sensor(s) in question and the wiring harness for:
  • Damaged insulation, frayed wires, or exposed conductors
  • Melted insulation from exhaust heat or contact with the exhaust
  • Loose or corroded connectors; bent pins
  • Signs of prior repair or splice work
• Check for wiring routing that may cause chafing against the exhaust pipes, heat shields, or engine components.

C. Check power supply and ground for the heater circuit

• Locate the O2 sensor heater circuit wires (usually two heater wires in the sensor connector).
• With the ignition on (engine off), test for battery voltage on the heater supply wire and continuity to ground as specified in the service manual. Some vehicles provide heater power when the ignition is on or when the engine is warming.
• Check the fuse/relay that powers the heater circuit. Replace any blown fuse and test the circuit again.

D. Measure heater resistance and current (sensor is in the circuit)

• Cool the sensor and disconnect the connector to measure heater resistance across the two heater pins. Typical heater resistance values vary by sensor type; many sensors read in the range of roughly 5–40 ohms. Compare to OEM spec in the service data.
• If you have the means to energize the heater circuit in a controlled test (some service tools simulate heater activation), verify that current flows and the resistance remains stable.
• If the heater shows infinite resistance (open circuit) or very low resistance (short), the sensor is likely bad.

E. Check for ground integrity and PCM control

• A poor ground can cause heater circuit symptoms; test for a solid ground path on the sensor and relevant PCM grounds.
• If power and ground test good but the heater still doesn’t energize, the issue could be a PCM control fault or a wiring fault that the test did not uncover.

F. Decide on repair approach

• If the heater circuit shows an open or short, or the connector is damaged beyond repair, replace the O2 sensor (Bank 2 Sensor 1 as labeled by the system).
• If wiring is damaged, repair or replace the harness/connector and reseal to prevent future corrosion.
• If the fuse/relay is defective, replace it and re-test.
• If the sensor passes power/ground tests but the heater still doesn’t heat, consider PCM fault as a last resort and consult an electrical/system specialist or GM service information.

G. Post-repair testing

• Clear the MIL and run the engine to operating temperature in normal drive conditions.
• Re-scan for codes and watch live O2 sensor data to ensure the sensor heats quickly (showing a rapid rise in sensor voltage when warmed).
• Drive through a few cycles (cold start and hot restart) to verify the issue does not reappear.

H. Malibu-specific notes

• If your Malibu’s engine configuration truly has only one bank (typical for inline-4), P0155 may indicate a mislabeling or an unusual wiring configuration. In that case, rely on OEM service data to confirm the sensor locations and bank mapping. If you cannot confirm with the service data, consult a GM dealer or a shop with GM scan and wiring diagrams to avoid misdiagnosis.

RELATED CODES

• O2 Sensor Heater Codes (Bank 1): P0135, P0136, P0137, P0138
• O2 Sensor Heater Codes (Bank 2): P0155 (current focus), P0156, P0157, P0158
• Other O2 sensor and fuel-related codes that can appear with O2 heater faults:
  • P0130–P0134 (O2 sensor circuit issues for Bank 1)
  • P0141 (O2 sensor heater Bank 1 Sensor 2)
  • P0150–P0154 (O2 sensor Bank 2 sensor 1/2)
  • P0420 (Catalyst system efficiency) and P0430 (Catalyst efficiency Bank 2) may appear if the oxygen sensor readings become unreliable

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by shop, region, and sensor type. The following are typical ranges you might expect as of 2025.

• O2 upstream sensor (Bank 2 Sensor 1) replacement

  • Parts: $40–$180 (OEM or aftermarket; higher for OEM)
  • Labor: 0.5–1.5 hours (depending on access)
  • Total: roughly $120–$350

• O2 sensor harness repair (wiring/connector repair only)

  • Parts: $10–$60 (connector or heat-shrink, sleeves, new terminals)
  • Labor: 0.5–1.5 hours
  • Total: roughly $100–$260

• O2 sensor heater circuit fuse/relay replacement

  • Parts: $5–$40 (fuse/relay; sometimes included in labor)
  • Labor: 0.2–0.6 hours
  • Total: roughly $60–$120

• PCM/ECM fault (less common)

  • Parts: $500–$1100 (new OEM)
  • Labor: 2–4 hours
  • Total: roughly $1000–$1700
  • Note: PCM replacement for an O2 heater issue is uncommon; use as a last resort after wiring/sensor checks

• Diagnostic/testing fees

  • If performed at a shop without prior diagnosis, diagnostic fees commonly range from $75–$150 (may be waived with repair at the same shop)

• Recurring costs

  • If multiple sensors or additional emissions systems require attention, total repair costs can rise accordingly.

DIY VS PROFESSIONAL

• DIY-friendly tasks (if you’re comfortable with electrical testing and have the right tools):
  • Visual inspection of sensor wiring and connectors
  • Checking for obvious damaged wiring, loose connectors, or corrosion
  • Verifying fuse/relay status (with proper safety)
  • Basic resistance checks of the heater circuit with a multimeter (requires a wiring diagram)
  • Replacing a faulty O2 sensor if you can access it safely and have replacement parts
• Tasks better left to a professional:
  • Diagnosing intermittent heater circuit faults that require ECU-level diagnostic commands or the OEM service data (to confirm bank mapping)
  • Precise heater circuit current/voltage testing and sensor verification using labs tools
  • PCM-related faults or when a sensor replacement doesn’t clear the code
• Safety notes:
  • Work carefully around the exhaust system and hot components
  • When measuring live circuits, follow proper electrical safety and disconnect battery if specified by the service manual

PREVENTION

• Regularly inspect oxygen sensor wiring and harnesses during routine maintenance (especially near exhaust heat sources)
• Use high-quality O2 sensors and avoid cheap substitutes that can fail prematurely
• Maintain proper engine maintenance (air filter, fuel injectors, ignition) to minimize abnormal exhaust conditions that can affect O2 sensor readings
• Address EVAP/fuel system issues promptly; persistent misfires or rich/lean conditions can stress O2 sensors
• Treat exhaust leaks promptly; leaks can alter sensor readings and lead to false heater faults
• Keep the vehicle updated with OEM-recommended service procedures and software updates if applicable

Important data note

• Recalls: No recalls found in the NHTSA database for this Malibu model/year in the provided data.
• Complaint data: The dataset includes two owner complaints for different codes (P0302 and P0420). There is no direct P0155 entry in the supplied data, so the guide uses standard OBD-II diagnostic logic for P0155 and Malibu-specific considerations.

If you’re dealing with a P0155 on a 2017–2023 Chevrolet Malibu, use this guide as a structured starting point. Begin with a careful sensor/wiring inspection and verify sensor location against the actual engine/bank layout for your exact build. If you’re not comfortable performing electrical diagnostics, or if the issue isn’t resolved after a sensor replacement and wiring check, seek a qualified mechanic or GM dealer to perform an in-depth diagnostic using OEM service information.