Code
P1A44
Generic
P — Powertrain
Inverter Temperature Sensor Circuit Range/Performance
Views:
UK: 10
EN: 14
RU: 8
AI status
Completed
Completed
100%
Causes
- Faulty inverter temperature sensor (open, shorted or out-of-spec thermistor)
- Damaged, corroded, or disconnected wiring/connector between sensor and inverter control module
- Short to power or short to ground in the signal or reference circuit
- Poor or missing sensor ground or reference voltage
- Contamination (coolant ingress, corrosion) at sensor or connector
- Intermittent contact due to vibration or wiring chafing
Symptoms
- Malfunction Indicator Lamp (MIL) or DTC P1A44 stored
- Inverter reduced power or torque limit (derate)
- Hybrid/EV system entering limp or limited-operation mode
- Incorrect or erratic inverter temperature reading in scan data
- Possible cooling system warnings if sensor monitors coolant around inverter
- Vehicle may refuse to enter EV/hybrid drive or charge modes
What to check
- Read and record all stored codes and freeze-frame data with a scan tool
- Confirm code is current (not pending) and note conditions when fault set (ambient/temp/load)
- Visual inspection of inverter area: wiring harness, connectors, sensor body for damage or contamination
- Check for related DTCs (charging, coolant pump, other temp sensors)
- Inspect service information for wiring diagrams, pinouts, and sensor type/specs
- Verify safety procedures for high-voltage systems before probing/instrumenting
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases or increases with temperature depending on design) — consult OEM spec
- Typical open-circuit signal behavior: voltage may be in the 0.1–4.9 V range (manufacturer-specific)
- Typical resistance example (generic): ~10 kΩ at 25 °C for many NTC sensors — actual values vary; check factory chart
- Reference voltage commonly 5 V or an internal pull-up in inverter module — confirm with wiring diagram
- Expected dynamic behavior: smooth, monotonic resistance/voltage change when sensor is heated/cooled; no intermittent jumps
Diagnostic algorithm
- Safety: Disable high-voltage system and follow manufacturer HV isolation steps before touching inverter hardware.
- Capture data: Use a scan tool to read P1A44 and related codes, record freeze-frame, live inverter temperature, and reference voltages/signals.
- Visual: Inspect sensor, connector and harness for corrosion, coolant residue, bent pins, heat damage or chafing. Repair obvious physical damage.
- Connector power/ground: With ignition/vehicle in service mode per manual, backprobe connector and confirm reference voltage and ground at the sensor connector per service data.
- Signal verification: Measure sensor signal voltage with the system running (if safe) or resistance with sensor disconnected and ambient temperature recorded. Compare to factory spec or generic NTC curve.
- Temperature stimulation: Gently heat (heat gun/hot water) or cool (ice pack) the sensor while monitoring signal/resistance for smooth change. No change or sudden jumps indicate fault.
- Wiring checks: Perform continuity, short-to-power and short-to-ground checks between sensor connector and inverter control module pins. Wiggle harness to reproduce intermittent faults.
- Repair: If sensor out-of-spec or wiring damaged, replace sensor or repair wiring/connector. If sensor and wiring good, suspect inverter/control module internal fault — refer to service manual for module-level tests or replacement.
- Clear codes and road/test under conditions that previously set the code to verify repair. If code returns, escalate to module bench testing or consult OEM technical support/TSB.
Likely causes
- Sensor thermistor drift or failure
- Open/short in signal wire or damaged insulation
- Loose/poor connector pin or corrosion allowing high resistance
- Loss of reference supply or ground from inverter control module
- Coolant leak wetting sensor/connector (if inverter coolant-cooled)
Fault status
Status
Inverter Temperature Sensor Circuit Range/Performance — temperature sensor or circuit out of expected range; may cause inverter derate or limited operation.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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