A/C Refrigerant Pressure Sensor "B" Circuit High
The A/C refrigerant pressure sensor B circuit is reading a voltage signal that is higher than the expected operating range. This prevents the engine control module from accurately monitoring refrigerant pressure, which disrupts proper A/C system operation and compressor engagement.
What You Might Notice
- A/C compressor not engaging or cycling improperly
- Inaccurate or fluctuating cabin air temperature
- Limited or no cold air from HVAC vents
- HVAC system operating abnormally or erratically
- Check Engine Light illuminated on dashboard
Most Common Causes
- 1
Defective A/C refrigerant pressure sensor
The sensor may have failed internally or developed a short circuit, causing it to send a continuously high voltage signal to the ECU.
- 2
Damaged wiring or connector corrosion
Open circuits, short-to-voltage conditions, or corroded connectors in the sensor circuit can cause abnormally high voltage readings at the ECU.
- 3
Low refrigerant pressure or system leak
If refrigerant has leaked out, the actual pressure drops while the sensor may malfunction and report falsely high values.
- 4
ECU or Body Control Module malfunction
A faulty engine control module or body control module may misinterpret normal sensor signals as high voltage conditions.
How to Diagnose It
- 1
Check Defective A/C refrigerant pressure sensor — The sensor may have failed internally or developed a short circuit, causing it to send a continuously high voltage signal to the ECU.
- 2
Check Damaged wiring or connector corrosion — Open circuits, short-to-voltage conditions, or corroded connectors in the sensor circuit can cause abnormally high voltage readings at the ECU.
- 3
Check Low refrigerant pressure or system leak — If refrigerant has leaked out, the actual pressure drops while the sensor may malfunction and report falsely high values.
- 4
Check ECU or Body Control Module malfunction — A faulty engine control module or body control module may misinterpret normal sensor signals as high voltage conditions.
How to Fix It
- 1
Test and replace A/C refrigerant pressure sensor
Use a multimeter to verify the sensor output voltage is outside normal range (typically 0.5–4.5V). If faulty, replace the sensor and retest system function.
- 2
Inspect and repair wiring and connectors
Visually inspect the sensor wiring harness and connector for damage, corrosion, or loose pins. Repair or replace damaged wiring and clean corroded connectors.
- 3
Check A/C system refrigerant level and integrity
Perform a refrigerant pressure test to confirm actual system pressure is within specification. If low, perform leak detection and repair any leaks, then recharge the system.
- 4
Verify or replace ECU/BCM if necessary
If wiring, connectors, and sensor test normal, reprogram or replace the engine control module or body control module after consulting vehicle service documentation.
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