U355D
Expander Inlet Pressure Sensor 1 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
- 5D
- FaultThe specific fault in that area
What it means
U355D is defined under the generic SAE J2012 list as Expander Inlet Pressure Sensor 1 Circuit. A control unit has flagged a fault in the signal or circuit of the pressure sensor on the inlet side of an expander. Typically the signal was out of range, missing, or not plausible. Which system the expander belongs to (for example a refrigerant or heat pump loop, or another energy-recovery or air-handling system) depends on the vehicle, so check the manufacturer's information for the specific model.
Symptoms
- Warning light on the dashboard, or a system fault message
- Reduced performance or a limited operating mode in the system the expander serves
- Poor cabin heating or cooling, if the expander is part of a climate or heat pump circuit
- Other fault codes stored in the same control unit or in linked units
- Fault that comes and goes, especially with vibration, heat or damp
Possible causes
- Wiring fault in the sensor circuit (open circuit, short to earth, short to supply or chafed wires)likely
- Corroded, loose or damaged connector at the sensor or the control unitlikely
- Faulty expander inlet pressure sensor 1likely
- Low or high system pressure, or a leak, causing an implausible reading (depends on the system type)possible
- Low supply voltage or a poor earth feeding the sensor or control unitpossible
- Internal fault in the control unit that monitors the sensorrare
- Outdated control unit software where the manufacturer has issued a fix for this faultrare
How to diagnose
- Read all stored and pending codes and record the freeze frame data, noting any related codes or voltage faults.
- Check the manufacturer's information to identify which system and which sensor 'Expander Inlet Pressure Sensor 1' refers to on this model.
- Visually inspect the sensor, its connector and the wiring for damage, chafing, corrosion, moisture or signs of leaks.
- Check the battery condition and charging voltage, and the relevant earth connections.
- With the sensor live, view its pressure reading and compare it with the expected value for the conditions and with other pressure data if available.
- Test the sensor supply, earth and signal wires for continuity, shorts and correct voltage against the wiring diagram.
- Check the actual system pressure with suitable equipment to separate a real pressure fault from a sensor fault.
- Check for software updates or technical bulletins for the control unit, then clear the codes and retest.
How to fix
- Repair or replace damaged wiring and fix any chafing or routing problems.
- Clean, repair or replace corroded or loose connectors and terminals.
- Replace the expander inlet pressure sensor if it tests faulty or reads implausibly against the actual pressure.
- Correct any underlying system pressure fault or leak found, following the manufacturer's procedure.
- Restore good battery voltage and earth connections if low voltage is found.
- Update the control unit software only if the manufacturer lists it as a fix, or replace the unit if it is confirmed faulty.
Can I keep driving?
The car can often be driven for a short time, but book a diagnosis soon as the affected system may run in a limited mode. Stop and seek help if there are other warnings, loss of power, or signs of a leak or overheating.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.