P2516 — Air conditioning pressure sensor signal is invalid

The air conditioning system's refrigerant pressure sensor is sending a signal that the car's computer finds impossible or inconsistent. This usually means the sensor is faulty, the wiring has a problem, or the system has an unusual pressure reading.

Common causes

The cause is almost always one of a few things. Here they are — P2516 rarely comes from anything outside this list:

• Faulty refrigerant pressure sensor
• Damaged or corroded wiring/connectors
• Low or incorrect refrigerant level
• Faulty AC control module
• Pressure sensor circuit short or open

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Check and clean sensor wiring and connectors
2. Test sensor signal and replace if faulty
3. Check refrigerant level and recharge if low
4. Inspect AC control module for faults
5. Replace refrigerant pressure sensor if needed

That is what holds for P2516 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.