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DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P2517

P2517A/C Refrigerant Pressure Sensor 'B' Circuit Low

P2517 indicates that the powertrain control module (PCM) has detected a low-voltage signal on the air conditioning (A/C) refrigerant pressure sensor 'B' circuit, which typically measures high-side pressure. The PCM compares this signal to expected values and sets the code when the voltage falls below the calibrated threshold, indicating a possible short to ground, open circuit, or sensor failure.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The A/C compressor may not engage, resulting in no cold air from the vents.
  • The A/C compressor clutch may cycle rapidly or not engage at all.
  • The check engine light (malfunction indicator lamp) illuminates.
  • In some vehicles, the cooling fans may run continuously or not at all.
  • Often no symptoms besides the warning light, especially if the sensor signal is only intermittently low.
  • The climate control system may default to a fail-safe mode, such as disabling A/C operation.

Common causes, most likely first

  1. Faulty A/C refrigerant pressure sensor 'B' (internal short or failure).
  2. Damaged or corroded wiring in the sensor 'B' circuit (short to ground or open circuit).
  3. Loose or corroded electrical connector at the sensor or PCM.
  4. Low refrigerant charge causing abnormal pressure readings (though this typically sets a different code).
  5. PCM internal fault (rare, but possible if all other circuits test good).
  6. Aftermarket accessories or improper wiring repairs interfering with the sensor signal.
  7. Moisture intrusion into the sensor connector or wiring harness.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in the A/C and PCM systems.
  2. Visually inspect the A/C refrigerant pressure sensor 'B', its connector, and wiring for damage, corrosion, or loose pins.
  3. Measure the sensor reference voltage and signal voltage at the connector with a digital multimeter (DMM) and compare to manufacturer specifications.
  4. Check the sensor's ground circuit for excessive resistance or an open circuit.
  5. Test the sensor's resistance or voltage output with a pressure gauge and compare to a known-good sensor or specification.
  6. If the sensor is faulty, replace it and clear the code; if wiring is faulty, repair the harness and re-test.
  7. After repairs, clear codes and verify the A/C system operates correctly with no return of the code.

Don't overlook the refrigerant charge

  • A low refrigerant charge can cause the pressure sensor to read abnormally low, setting P2517 even when the sensor and wiring are intact.
  • The sensor 'B' circuit often shares a reference voltage or ground with other sensors, so a fault elsewhere can pull the signal low.
  • Intermittent code settings may be caused by a chafed wire that only shorts when the engine moves or the harness flexes.
  • Some vehicles use the A/C pressure sensor signal for cooling fan control, so a low signal can cause fan-related symptoms without an A/C complaint.
  • Replacing the sensor without checking the connector pins for corrosion or spread terminals often leads to a repeat failure.

Can I keep driving with P2517?

You can generally drive the vehicle with this code, but the A/C may not function, which could be uncomfortable in hot weather. Avoid using the A/C until repaired, and address the issue promptly to prevent potential compressor damage from operating with incorrect pressure readings.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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