Code
P0055
LAND ROVER
P — Powertrain
Heated oxygen sensor heater resistance (bank 1, sensor 3)
Views:
UK: 12
EN: 25
RU: 27
AI status
Completed
Completed
100%
Causes
- Open or high-resistance heater element inside the O2 sensor
- Broken or corroded wiring or connector for the heater circuit
- Blown fuse or faulty relay supplying the heater circuit
- Poor ground or high-resistance ground connection
- ECM/PCM driver fault for the heater circuit
- Aftermarket or incorrect replacement sensor with wrong heater characteristics
Symptoms
- Check Engine Light (MIL) illuminated
- Possible poor fuel trim control or reduced fuel economy
- Failed emissions test
- Rough idle or drivability issues if system relies on downstream heater status
- Repeated or persistent related DTCs
What to check
- Read and record freeze frame and live data; note heater status and any related codes
- Visual inspection of sensor, connector, and wiring for damage, corrosion, or heat exposure
- Check related fuses and relays for continuity and operation
- Measure resistance of sensor heater at the sensor connector (with sensor disconnected from harness)
- Backprobe harness to verify key-on heater supply voltage and ground while commanding heater on with a scan tool
- Perform wiggle test on harness while monitoring heater circuit for intermittent faults
Signal parameters
- Typical heater resistance (varies by sensor): commonly in the low ohms range — often roughly 2–20 Ω (consult vehicle service data for exact spec)
- Open-circuit/infinite resistance indicates an open heater element
- Very low resistance (
- Heater supply voltage with ignition ON and heater commanded ON: near battery voltage (~11–14 V) at the supply circuit
- Heater current when active: can be several hundred mA up to a few amps depending on sensor; ECM may use PWM/duty control
Diagnostic algorithm
- Retrieve freeze frame/live data and any additional codes (check for related heater or sensor codes).
- Perform a careful visual inspection of bank 1 sensor 3, its connector, harness routing, and nearby heat sources for damage.
- Check fuses/relays that feed the O2 heater circuit; replace if blown and retest.
- With ignition off, disconnect the O2 sensor connector and measure heater resistance across the heater pins at the sensor. Compare to spec. Infinite = open; very low = short.
- If heater resistance at the sensor is within spec, backprobe the harness connector with ignition ON and measure supply voltage to the heater circuit (should be battery voltage when circuit is commanded).
- Use a capable scan tool to command the O2 sensor heater ON while monitoring voltage/current and ground control. Verify the ECM is commanding the heater and that supply/ground are present.
- Check continuity of the ground and power circuits between the sensor connector and the ECM/fuse. Repair any high-resistance or open sections.
- Wiggle the harness while monitoring circuit to identify intermittent faults or broken conductors.
- If wiring and power/ground are good but heater resistance is out of range, replace the oxygen sensor (use OEM or specified part).
- After repair, clear codes and road test; verify the heater operation and that the code does not return.
Likely causes
- Damaged connector (corrosion, bent pins) at bank 1 sensor 3
- Broken/chafed harness between sensor and ECM (open or intermittent)
- Open heater element in the sensor (sensor failure)
- Fuse related to oxygen sensor heater blown or weak ground
- Connector shorted to chassis ground or power
Fault status
Status
Heater circuit resistance out of range for heated oxygen sensor (Bank 1, Sensor 3). Possible open, short, or high-resistance heater circuit or failed sensor.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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