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DTC codes / B02xx · Airbags, seats, doors, lights and comfort systems / B0288

B0288HVAC A/C Pressure Sensor Circuit

B0288 indicates that the HVAC (heating, ventilation, and air conditioning) control module has detected an abnormal condition in the air conditioning refrigerant pressure sensor circuit. The module monitors the sensor's signal voltage and sets this code when the voltage falls outside the expected range for the current operating conditions, which may be due to an open, short, or erratic signal.

SystemBody
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

  • The air conditioning compressor may not engage at all, resulting in no cold air from the vents.
  • The A/C compressor may cycle rapidly or stay engaged continuously, leading to poor cooling or possible component damage.
  • The HVAC control head may display a flashing or steady warning indicator, or the climate control panel may become unresponsive.
  • In some vehicles, the engine cooling fan may run constantly or not at all because the pressure sensor signal is shared with the fan control strategy.
  • Often no symptoms besides the warning light, especially if the system defaults to a fail-safe mode that still provides some cooling.
  • The A/C may work intermittently, cutting out during acceleration or at idle when pressure changes are most pronounced.

Common causes, most likely first

  1. A failed A/C pressure sensor (also called a refrigerant pressure transducer) that no longer produces a correct voltage for a given pressure.
  2. Damaged, chafed, or corroded wiring in the sensor circuit, particularly at the connector or where the harness passes near hot or moving components.
  3. A poor electrical connection at the sensor or HVAC control module, often due to water intrusion or loose terminals.
  4. Low refrigerant charge, which can cause the sensor to read outside the expected range and set the code even though the sensor itself is functional.
  5. A faulty HVAC control module that misinterprets a valid sensor signal or has an internal driver fault.
  6. Aftermarket accessories or previous repairs that tapped into the sensor wiring and disturbed the reference or signal voltage.

How to diagnose and fix it

  1. Verify the refrigerant charge using a manifold gauge set or recovery machine; low charge is a common cause and must be ruled out before condemning electrical parts.
  2. Inspect the A/C pressure sensor connector and the harness for corrosion, loose pins, or chafed wires, and repair any damage found.
  3. Backprobe the sensor connector and measure the signal voltage with the key on and A/C requested; compare to the manufacturer's expected range for the ambient temperature.
  4. Check the sensor's reference voltage and ground circuits at the connector to confirm the module is supplying the correct 5-volt reference and a good ground.
  5. If the signal voltage is stuck or out of range, remove the sensor and test it with a known pressure source or compare its resistance to a known-good unit.
  6. Clear the code and operate the A/C system through several cycles to see if the code returns; if it does, replace the pressure sensor and recheck.
  7. If the sensor and wiring test good but the code persists, diagnose the HVAC control module and its software calibration before replacement.

Pressure sensor faults that mimic other A/C problems

  • A low refrigerant charge often sets B0288 because the pressure sensor reads below the expected range, so technicians who replace the sensor without checking charge frequently see the code return.
  • The A/C pressure sensor signal is often shared with the engine cooling fan control strategy, so a fan that runs constantly or not at all can be the first clue to a sensor circuit fault.
  • Some vehicles use a linear pressure sensor while others use a simple switch; the code definition covers both, and the diagnostic steps differ, so confirm the system type before testing.
  • Corrosion inside the sensor connector caused by water intrusion from the cowl or splash area is a common hidden cause that visual inspection from above may miss.
  • A failed sensor can sometimes read a plausible pressure at idle but drop out under load, so a static voltage check may pass while a live data test during A/C operation reveals the fault.

Can I keep driving with B0288?

You can usually drive the vehicle with B0288 set, but the air conditioning may not work or may cycle poorly, and in some cars the engine cooling fan strategy is affected. Avoid long trips in hot weather or heavy traffic until the fault is repaired, and do not continue driving if the engine temperature gauge climbs above normal.

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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