Body, generic

B0288 HVAC A/C Pressure Sensor Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

A search found B0288 in no J2012 list and in no carmaker's service data; it stays unconfirmed. The refrigerant pressure sensor it names sits on the high-pressure line; its signal decides whether the compressor may run and how fast the cooling fan turns. On most cars the engine controller reads it and stores P0530–P0533. Saab's 9-3 with Trionic 8, for example, sets P0532 below 0.25 V and P0533 above 4.2 V, each for over 1 s with the engine running above −7 °C, and then cuts the A/C relay. Patent US9259992B2 routes the sensor to the engine module in the same way, and US5623835A uses it to drive the fan. A body code would only be used where the climate module reads the sensor itself.

Likely causes

Refrigerant pressure sensor failed or signal drifting
Sensor connector near the condenser corroded by road spray
5 V reference, ground or signal wire open or shorted
Very low refrigerant charge giving an implausible reading

Symptoms

  • Air conditioning blows warm because the compressor is disabled
  • Radiator fan runs constantly or at the wrong speed

Repair estimate

DifficultyEasyDIY possible
Parts and labour€50–250
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ac refrigerant pressure sensorac compressor relayhvac control module

Related codes

P0530P0532P0533B0292

References: saabwisonline.com, saabwisonline.com, patents.google.com, patents.google.com.