Wiring or connector fault in the air inlet pressure sensor circuit (open circuit, short, corrosion, chafed or loose pins); Faulty air inlet pressure sensor giving a signal that is out of range or implausible; Air leak, split hose or blocked pipe between the sensor and the intake or charge air system, giving a pressure reading that does not match expectations; Low or unstable supply voltage or poor earth affecting the sensor or the module that reads it; Communication fault between the module that reads the sensor and the engine control unit, if the value is shared over the network; Fault inside the engine control unit or the module that processes the sensor signal; Outdated software in the control unit where the manufacturer has published a known fix.

U3559

Air Inlet Pressure Sensor Circuit.

Generic
Network
Generic code
Medium severity

How this code is built

U: SystemNetwork
3: Defined bySAE, the same on every car
5: AreaNetwork area 5
59: FaultThe specific fault in that area

What it means

U3559 is listed here with the meaning 'Air Inlet Pressure Sensor Circuit'. The U prefix normally points to a control module or data communication fault rather than a plain sensor fault, and the U3xxx range is largely left to manufacturers in SAE J2012. The control unit has most likely seen an implausible, missing or incorrectly communicated air inlet (intake or boost) pressure signal. How it detects this, and whether the sensor is wired directly or its value is passed over the network, depends on the make, model and engine.

Symptoms

Engine warning light on
Loss of power or reduced boost, often with the car in limp mode
Poor or uneven idle
Hesitation or poor throttle response
Rough running, or more smoke or poorer fuel economy than usual
Other stored fault codes, possibly including communication or boost pressure codes

Possible causes

Wiring or connector fault in the air inlet pressure sensor circuit (open circuit, short, corrosion, chafed or loose pins)likely
Faulty air inlet pressure sensor giving a signal that is out of range or implausiblelikely
Air leak, split hose or blocked pipe between the sensor and the intake or charge air system, giving a pressure reading that does not match expectationspossible
Low or unstable supply voltage or poor earth affecting the sensor or the module that reads itpossible
Communication fault between the module that reads the sensor and the engine control unit, if the value is shared over the networkpossible
Fault inside the engine control unit or the module that processes the sensor signalrare
Outdated software in the control unit where the manufacturer has published a known fixrare

How to diagnose

Read all stored and pending codes with freeze frame data, and note any other communication, sensor supply or boost codes that appeared with U3559.
Look up the manufacturer's definition of U3559 for this model and engine, as the generic list does not fully define U3xxx codes.
Check the battery condition and charging voltage, and the main earths, as low voltage can set network and sensor faults.
Inspect the sensor connector, wiring and nearby loom for damage, heat, rubbing, water ingress and corrosion.
Check the intake and charge air hoses, clamps and the sensor seal for leaks, splits or blockages.
View live data for air inlet pressure with the engine off (it should read close to ambient pressure) and compare with the reading at idle and under load.
Check the sensor supply voltage, signal and earth with a multimeter against the manufacturer's wiring diagram, and test for continuity and shorts.
If the wiring and sensor test fine, check the data link and the control unit's power and earth, and check for software updates from the manufacturer.

How to fix

Repair or replace damaged wiring, and clean or replace corroded or loose connector terminals.
Replace the air inlet pressure sensor if its readings or electrical values are out of specification.
Repair or replace leaking, split or blocked intake and charge air hoses and refit the sensor seal correctly.
Fix charging system, battery or earth faults that cause unstable voltage.
Repair the communication fault found on the data link, or replace the affected module only after confirming it is faulty.
Apply a manufacturer software update only if it is a known fix for this fault.

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but it may be in limp mode with reduced power, which can be unsafe when overtaking or pulling out. Get it diagnosed soon, and stop if power loss becomes severe or the engine runs very roughly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.