P0EC2

Code

Generic P — Powertrain

A/C Refrigerant Temperature Sensor B Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 27 RU: 29

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Page language: EN

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