P2516

Code

Generic P — Powertrain

A/C Refrigerant Pressure Sensor B Circuit Range/Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 38 RU: 16

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Page language: EN

Causes

Open or shorted wiring in the sensor B circuit
Corroded, loose or water-damaged connector at the pressure sensor
Faulty A/C refrigerant pressure sensor (Sensor B)
Poor sensor ground or missing reference voltage from the ECU
Extreme refrigerant pressure (very low or very high) due to system leak/blockage or overcharge
Contaminated or mechanically damaged sensor element

Symptoms

MIL/Check Engine lamp illuminated
Erratic A/C operation: intermittent compressor engagement or constant lockout
Reduced or no cabin cooling
A/C clutch cycles rapidly or does not engage
Stored freeze-frame data showing abnormal pressure PID values

What to check

Read and record freeze frame and live data PIDs for refrigerant pressure sensor B and related sensors
Scan for additional A/C or HVAC codes (sensor A, clutch control, refrigerant temperature)
Visually inspect sensor, connector and wiring harness for damage, corrosion, or water intrusion
Backprobe sensor connector and measure reference voltage, signal voltage and ground at key off and with ignition on/AC on
Check continuity and resistance between sensor ground and chassis ground
Check for shorts to power or ground in the signal circuit

Signal parameters

Typical sensor architecture: 5 V reference supply, ground, and signal output to PCM (varies by vehicle)
Expected signal: approximately 0.5–4.5 V across normal operating pressures (exact pressure-to-voltage curve is vehicle-specific)
Low-pressure condition: signal approaches lower end (~0.2–0.8 V)
High-pressure condition: signal approaches upper end (~4.0–4.8 V)
Open circuit: signal reads near 0 V or pinned at reference voltage if shorted to supply

Diagnostic algorithm

Confirm stored code and note freeze-frame data. Check for pending or related codes.
With ignition ON (engine off), observe live data for refrigerant pressure sensor B — note signal voltage and compare to sensor A if present.
Visually inspect sensor, connector and harness for damage, corrosion, or signs of refrigerant/oil leakage. Repair or replace damaged connectors/wiring as needed.
Backprobe connector: verify reference voltage (typically 5 V) at the sensor supply terminal, good ground, and measure signal voltage. If reference or ground missing, trace to PCM and repair.
Check for short to ground or battery: disconnect sensor and measure resistance from signal to ground and to battery; look for unintended low resistance.
With A/C off and then on (or with system pressurized via service process), monitor signal change; if signal does not change while system pressure changes (checked with gauges), suspect sensor failure.
If wiring and reference/ground are good but signal is implausible, replace the pressure sensor B. Clear codes and retest system performance and live data.
If fault returns after sensor replacement, perform PCM/ECU input circuit testing per manufacturer procedures or seek PCM replacement only after ruling out wiring and sensor faults.
Verify refrigerant charge and repair leaks/blockages if extreme pressures caused the out-of-range reading.

Likely causes

Damaged wiring or poor connector contact at the sensor
Failed refrigerant pressure sensor (B)
Low refrigerant charge or system restriction causing out-of-range pressure readings

Fault status

⚠️ Status

A/C Refrigerant Pressure Sensor B Circuit — Range/Performance fault. The sensor signal is outside expected limits or the circuit is open/shorted, causing incorrect refrigerant pressure reporting.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours