Code
P0EC2
Generic
P — Powertrain
A/C Refrigerant Temperature Sensor B Circuit High
Views:
UK: 10
EN: 20
RU: 15
AI status
Completed
Completed
100%
Causes
- Open circuit or wiring short to battery voltage in refrigerant temperature sensor B circuit
- Faulty refrigerant temperature sensor (thermistor) B
- Corroded, loose or damaged connector or pin at sensor or control module
- Poor or missing ground for the sensor circuit
- Short to another powered circuit
- Faulty HVAC control module / PCM (less common)
Symptoms
- Malfunction Indicator Lamp (MIL) or A/C related warning lamp illuminated
- Reduced A/C performance or compressor disabled as a protective strategy
- Intermittent or no cooling from HVAC system
- Unreliable HVAC automatic climate control behavior
- DTC stored in engine/PCM or HVAC module memory
What to check
- Retrieve DTC with a scan tool and record freeze-frame/live data for refrigerant temperature sensor B
- Visually inspect sensor B connector and wiring for damage, corrosion, pinch points or disconnection
- Back-probe connector and measure sensor circuit voltage with ignition ON (refer to vehicle-specific chart)
- Measure sensor resistance (with sensor disconnected) and compare to expected values at known temperatures if service data available
- Wiggle wiring harness while observing live data/LED to reproduce fault
- Check for related codes (other A/C temp sensor circuits, HVAC module faults, power/ground circuits)
Signal parameters
- Typical signal: 0–5.0 V sensor input to module (varies by manufacturer)
- Most refrigerant temperature sensors use a thermistor (usually NTC): resistance decreases as temperature increases
- Typical resistance reference: often in the 1 kΩ–100 kΩ range depending on design (consult vehicle service data for exact curve)
- A 'high' circuit code means measured voltage is above the expected maximum or sensor resistance indicates an abnormally high temperature/out-of-range value
Diagnostic algorithm
- Use a scan tool to confirm P0EC2 and view live refrigerant temperature B data. Clear codes and see if code returns.
- Perform visual inspection of sensor B, connector, and wiring for damage, corrosion, or disconnected pins. Repair any obvious issues.
- With connector attached, back-probe the signal and ground wires; verify reference voltage and ground are present with ignition ON. Compare to service specifications.
- If power/ground are correct, disconnect the sensor and measure the thermistor resistance across its terminals. Check resistance at ambient and after warming/cooling sensor (e.g., ice water / warm water) to confirm change.
- If resistance/voltage are out of spec or the sensor does not change with temperature, replace sensor B and retest.
- If sensor tests good, inspect wiring for short to battery (high voltage) between sensor connector and module. Repair wiring harness as needed.
- Perform wiggle tests while monitoring live data to identify intermittent shorts or opens.
- If wiring and sensor check good, test module input pin for correct behavior or substitute/inspect HVAC/PCM module per manufacturer procedures.
- After repairs, clear codes and verify proper system operation and that the code does not return in normal cycling.
Likely causes
- Broken or pinched wiring between sensor B and the module causing a short to power
- Contaminated/corroded connector causing high resistance or intermittent high voltage reading
- Thermistor element failed internally and reporting high voltage
- Poor ground or missing reference voltage
- Aftermarket work or service left connector or harness damaged
Fault status
Status
A/C refrigerant temperature sensor B circuit reported high signal. MIL may be set and A/C system may be limited or disabled until condition is resolved.
Repair difficulty: Medium
Diagnostic time: 0.5–1.5 hours
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