P0043 on 2014-2016 Land Rover LR4: Heater Circuit Fixes for O2 Sensor

What's Unique About the 2014-2016 Land Rover LR4

For this specific Land Rover LR4 generation and its platform mates with the 3.0L SC V6, P0043 is frequently not just a random part failure. Land Rover has issued multiple Technical Service Bulletins (TSBs), such as LTB00671NAS3, acknowledging that the post-catalyst oxygen sensors are prone to failure from 'thermal shock' when water hits the hot sensor. Furthermore, some cases are caused by a software error that makes the system overly sensitive, and the official repair procedure often involves both replacing the sensor and updating the engine control module's software to prevent future failures.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on
• Failure to pass a vehicle emissions test
• Slightly decreased fuel economy in some cases
• No noticeable impact on engine performance or drivability

Most Likely Causes

1. Failed Heated Oxygen Sensor (Bank 1, Sensor 3) 🎬 Watch: A helpful guide on fixing the P0043 fault code. 🔴 High Probability Land Rover TSBs LTB00671NAS3 and others state these sensors are susceptible to failure from thermal shock (water contact). TSB SSM72448 also notes these sensors frequently fail with no other fault found in the circuit, pointing to an internal sensor issue.
   How to confirm: Disconnect the sensor and measure the resistance across the two heater circuit pins (often the two same-colored wires) using a multimeter. An open circuit (infinite resistance) or a reading far outside the typical 4-10 Ohm specification confirms failure. Visually inspect for a cracked ceramic insulator.
   Typical fix: Replace the Bank 1, Sensor 3 oxygen sensor. This is on the passenger side, furthest downstream. A 22mm or 7/8" oxygen sensor socket or wrench is required. The OEM part number is LR035750.
   Est. part cost: $70-$220
2. Outdated Powertrain Control Module (PCM) Software 🟡 Medium Probability → Shop Engine Control Module (ECM) TSB LTB00662 and LTB00671NAS3 were released specifically to address P0043 and other O2 sensor codes via a software update. The updated software adjusts the sensor monitoring strategy to be less susceptible to flagging a code from intermittent conditions like thermal shock. The official fix often pairs a sensor replacement with this software reflash.
   How to confirm: A Land Rover dealer or a specialized shop with access to the official SDD (Symptom Driven Diagnostics) software can check the vehicle's software version against the latest available version specified in the TSBs.
   Typical fix: Update the PCM software to the latest version. This is often performed at the same time as the sensor replacement to prevent the code from returning.
   Est. part cost: $0 (if part of a warranty or recall), $150-$300 (as a standalone dealer service)
3. Damaged Wiring or Connector ⚪ Low Probability The sensor's location under the vehicle exposes its wiring harness to road debris, heat, and moisture, which can lead to corrosion, chafing, or physical damage over time. Forum users often report these sensors are heavily rusted in place, suggesting a harsh environment.
   How to confirm: Visually inspect the wiring harness and connector for the Bank 1, Sensor 3 O2 sensor. Look for any signs of melting, chafing, corrosion, or loose pins. Check for 12-volt power at the connector's heater circuit supply wire with the ignition on.
   Typical fix: Repair the damaged section of wiring or clean/replace the connector.
   Est. part cost: $5-$50

Rare But Worth Checking

• Blown Fuse: While less common, it's a simple check. The O2 sensor heater circuits are protected by a fuse in the main fuse box. A blown fuse could indicate a short circuit in the wiring that needs to be addressed before replacing the sensor.
• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is extremely rare. Before condemning the PCM, all other possibilities (sensor, wiring, software) must be exhaustively ruled out. A PCM failure might also present with multiple other unrelated codes.

Diagnosis Steps

1. Scan the vehicle for OBD-II codes to confirm P0043 is present and note any other codes.
2. Perform a visual inspection of the Bank 1, Sensor 3 oxygen sensor (passenger side, rearmost), its connector, and its wiring harness. Look for any signs of damage, melting, or corrosion.
3. Check the fuse(s) related to the oxygen sensor heater circuits in the vehicle's fuse box.
4. With the ignition on (engine off), carefully test for 12V power at the heater circuit supply wire on the sensor's connector.
5. Disconnect the sensor and measure the resistance of the heater element within the sensor itself using a multimeter. Compare this reading to the manufacturer's specification (typically 4-10 Ohms). An open circuit (infinite resistance) indicates a failed sensor.
6. If the sensor and wiring test good, consult a dealer or qualified shop to check if a PCM software update is available and required per TSBs like LTB00671NAS3.
7. If replacing the sensor, use a 22mm (or 7/8") O2 sensor socket. Raising the vehicle to off-road height may provide sufficient access. A heat shield may need to be removed.

Parts You'll Likely Need

• Heated Oxygen Sensor (Bank 1, Sensor 3) (OEM #LR035750) — This is the most common failure point for code P0043 on this vehicle, as documented by multiple Land Rover TSBs citing thermal shock and manufacturing issues. It is the rearmost sensor on the passenger side.
  Trusted brands: Bosch (OEM supplier), Denso, NTK, Walker
  OEM price range: $150-$220
  Aftermarket price range: $70-$140

Related Codes That Often Appear With This One

• P0042 — This code is for 'HO2S Heater Control Circuit (Bank 1 Sensor 3)' and is often listed in the same TSBs as P0043, indicating a related fault in the same circuit.
• P0044 — This code is for 'HO2S Heater Control Circuit High (Bank 1 Sensor 3)' and points to the opposite condition (high voltage) in the same circuit, often sharing the same root causes like a faulty sensor or wiring.
• P0162, P0163, P0164 — These are codes for the corresponding sensor on the other engine bank (Bank 2, Sensor 3). They are listed in the same TSBs and have the same common causes, suggesting a systemic issue with the sensors used across the platform.

Technical Service Bulletins (TSBs) & Recalls

• SSM72448: Notes that P0043 may be set with no fault found upon diagnosis, pointing to an internal sensor failure.
• LTB00671NAS3: Identifies P0043 as relevant to post-catalyst heated oxygen sensors, attributes the cause to thermal shock, and recommends sensor replacement paired with a software update.
• LTB00662: Details a PCM software update for 2014 models to resolve P0043 and other O2 sensor codes.

Platform-Specific Known Issues

• TSB LTB00671NAS3: Explicitly addresses P0043 and other HO2S codes on the 3.0L SC V6. It states the cause may be 'thermal shock when water contacts the heated sensing element' and the action is to replace the affected sensor and perform a PCM software update.
• TSB SSM72448: This bulletin notes that for a wide range of O2 sensor codes including P0043, a diagnosis may find no fault with wiring, with the issue being the sensor itself. It was part of an investigation into sensor quality.
• TSB LTB00662: A specific PCM software update was released for 2014 LR4 models to address P0043 and other oxygen sensor codes caused by a software error.
• Thermal Shock Failures: Multiple bulletins and owner forums confirm the cause of sensor failure can be thermal shock from water contacting the hot sensor element, making it a design-related vulnerability.

Mechanic-Grade Diagnostic Values

• O2 Sensor Heater Element Resistance — expected: 4-19 Ohms when cold.. Failure: A reading of infinity (Open Loop) or 0 Ohms (short circuit) indicates a failed heater element.
• Heater Circuit Power Supply — expected: ~12V (Battery Voltage) at the harness-side connector with ignition on, engine off.. Failure: No voltage indicates a problem with the fuse or wiring upstream of the sensor.
• Downstream O2 Sensor Live Data Voltage (Healthy) — expected: Relatively stable voltage, typically between 0.6V and 0.8V when the catalytic converter is hot and working efficiently.. Failure: Voltage is stuck low (near 0.1V), stuck high (near 1.0V), or is completely flat and unresponsive.

Scan Tool Commands That Help

• Land Rover SDD (Symptom Driven Diagnostics): Configure existing module – Powertrain control module — This function is used to apply a software update to the PCM to address false or recurring O2 sensor codes, as specified in TSB LTB00671NAS3. It should be performed after replacing the faulty sensor.
• High-End Bidirectional Scanners (e.g., FOXWELL NT510 Elite): O2 Sensor Test / On-Board Monitor Test — Allows retrieval and viewing of O2 sensor monitor test results for the most recently performed tests from the vehicle's on-board computer. This can help confirm if the sensor is passing or failing its self-tests after a repair.

Wiring & Ground Locations

• Fuse 2 (Engine Compartment Fuse Box) — Located in the fuse box in the engine compartment.. A forum post indicates this fuse provides the direct battery supply to the heater circuit for all four O2 sensors. A blown fuse here would disable the heaters and could trigger P0043 and other heater codes.
• ECM Connector C0635, Pin 1 — This is a pin on one of the main connectors for the Engine Control Module (ECM).. According to a wiring diagram for a similar Land Rover V8, this specific pin controls the ground path for the downstream, right-hand bank (Bank 1) O2 sensor heater. A fault in the wire to this pin or an internal ECM driver fault would directly cause a P0043 code.
• Bank 1 Sensor 3 Connector — Underneath the vehicle on the passenger (right) side, downstream of the rearmost catalytic converter. The connector is usually attached to a bracket on the underbody.. This is the primary connection point for the sensor. It is exposed to the elements and is a common location for corrosion, moisture intrusion, or physical damage that can cause the P0043 low circuit voltage condition.

OEM Part Supersession History

• LR035750 → LR035750 is the current part number. — N/A
  Heads up: Part number LR035750 is listed for multiple positions (Front Upper, etc.) on different Land Rover models, but for the 2014-2016 LR4 3.0L V6, it is specified for the post-catalyst position. Ensure the correct sensor is ordered for Bank 1, Sensor 3. Cross-reference part numbers include CPLA-9F472-CC and CPLA-9F472-CA.

Model Year Variations Within This Range

• 2014: A specific PCM software update was released for 2014 model year LR4s (and other JLR models with the 3.0L V6) to address erroneous P0043 and other O2 sensor codes. This is detailed in TSB LTB00662. While later years also benefit from software updates, this TSB was particularly targeted at the 2014 models.