P0533 means the engine control module saw the A/C refrigerant pressure sensor A signal above its maximum acceptable voltage. The family is P0530 (circuit), P0531 (range or performance), P0532 (low) and P0533 (high). The sensor sits on the high-side refrigerant line or the receiver-drier and reports pressure so the module can engage the compressor, run the cooling fans and protect the compressor from over- or under-pressure. A three-wire sensor with a 5-volt reference reads high when its signal wire is open, its ground is lost, or it is unplugged.
Severity: low for driving. Can you keep driving? Yes. The engine runs normally. Most calibrations disable the compressor when the pressure reading is invalid, so the vents blow warm. Nothing is damaged by waiting, though on GM's trucks the same harness fault produces other symptoms that should not wait.
The GM vacuum pump pulley case
General Motors' preliminary information PIT5307 (versions through F, 2016 to 2019) covers the 2014 to 2017 Silverado 1500 and Sierra 1500 and 2015 to 2017 Tahoe, Suburban, Yukon and Escalade with the 5.3 L L83 or 6.2 L L86: check engine and ABS lights, a service suspension message, misfire, hesitation, low power, erratic shifting, no crank, A/C inoperative, a low oil level message, blown starter and A/C clutch fuses, and a list of codes that includes P0532 and P0533 alongside knock sensor, cam and crank sensor, oil pressure, reference voltage and chassis codes. The cause is the engine harness chafing at the vacuum pump pulley. The repair finds the rubbed section, repairs the wires and secures the harness clear of the pulley.
Mitsubishi's 2022 Outlander service manual revision (TSB-23-11-003, May 2023) added a full diagnostic section for P0533 for the 2.5 L engine, a reminder that the code has a defined procedure on most current vehicles.
Causes, in the order they are found
An open wire or a chafed harness on the sensor circuit, as in GM's case.
A connector unplugged or backed off after A/C or front-end work, or corroded from road spray on the front of the engine.
A lost ground or reference shared with other sensors, when several set codes at once.
The sensor with an open element.
The module, last.
A diagnostic order
- Record companion codes. P0533 with knock, cam, crank and oil pressure codes on a GM truck is the harness bulletin; P0533 alone is this circuit.
- Find the sensor on the high-side line and look at its connector.
- Key on, unplugged: about 5 V on the reference pin, under 0.1 V of drop on the ground pin, and the signal at the module's pull-up. Jumper reference to signal: the module should now read maximum pressure. If it still reads the ceiling with the jumper, the signal wire is open.
- Plug in and compare the sensor's reading with a gauge set on the high side, engine off. Agreement within a small margin means the sensor is fine and the fault was the connector or intermittent.
- Inspect the harness along the front of the engine, and at the vacuum pump pulley on the GM engines above.
- Repair the wire or connector, or replace the sensor only if it reads open, then clear and verify the compressor engages.
Frequently asked questions
Can I drive with a P0533 code?
Yes. The engine is unaffected. The A/C compressor is usually disabled while the pressure reading is invalid, so expect warm air until it is fixed.
Is P0533 the A/C pressure sensor?
Less often than the wiring. A high reading is what an open circuit looks like, and on 2014 to 2017 GM full-size trucks and SUVs GM traced it, with many other codes, to the engine harness chafing at the vacuum pump pulley. Test with the sensor unplugged and jumpered before replacing it.
Why did my A/C stop with P0533 but the refrigerant is full?
Because the module cannot see the pressure with the sensor circuit open, and it disables the compressor rather than run it blind. The charge is fine; the circuit is not.
How much does it cost to fix P0533?
A wire or connector repair is under an hour, more if the harness needs rerouting away from a pulley. The sensor is an inexpensive part, replaced without opening the system on most vehicles because it sits on a Schrader-type port.
Related codes
- P0530 / P0531 / P0532: A/C pressure sensor circuit, range, low.
- P0534: A/C refrigerant charge loss, the inference that depends on this sensor; see P0534.
- P0645 to P0647: A/C clutch relay circuit.
- P0641: sensor reference voltage A circuit, listed with P0533 in GM's harness bulletin.
The code number itself tells you the family and the domain; how to read an OBD2 code number explains what each character means.