Faulty charge air cooler outlet temperature sensor; Damaged, chafed or corroded wiring to the sensor, including short or open circuit; Poor connection at the sensor or control unit plug (loose, corroded or water in the connector); Oil, water or heat damage to the sensor or harness near the intercooler pipework; Fault in a module that reads or relays the sensor signal over the network, including power or earth problems; Internal fault in the control unit; Outdated or faulty control unit software where the manufacturer lists it as a known cause.

U355C

Charge Air Cooler Outlet Temperature 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
5C: FaultThe specific fault in that area

What it means

U355C is defined under the generic standard as a fault in the Charge Air Cooler Outlet Temperature Sensor circuit. The control unit that uses the charge air temperature did not get a valid or plausible signal or message from that sensor. This may be a wiring or sensor fault, or a communication problem between modules, depending on how the vehicle is set up. How the signal reaches the control unit varies by model and engine.

Symptoms

Engine warning light on
Reduced power or limp mode, especially under boost
Hesitation or flat acceleration when the engine is loaded
Poor fuel economy
Possible rough running or erratic boost behaviour
Other stored codes for charge air, boost or communication

Possible causes

Faulty charge air cooler outlet temperature sensorlikely
Damaged, chafed or corroded wiring to the sensor, including short or open circuitlikely
Poor connection at the sensor or control unit plug (loose, corroded or water in the connector)likely
Oil, water or heat damage to the sensor or harness near the intercooler pipeworkpossible
Fault in a module that reads or relays the sensor signal over the network, including power or earth problemspossible
Internal fault in the control unitrare
Outdated or faulty control unit software where the manufacturer lists it as a known causerare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note any related charge air, boost or communication codes.
Check the live charge air outlet temperature reading with the engine cold; it should be close to ambient and coolant temperature, and not fixed at an extreme value.
Visually inspect the sensor, its connector and the harness for chafing, heat damage, oil contamination, corrosion or loose pins.
Check the intercooler pipes and the area around the sensor for leaks, oil ingress or damage that could affect the sensor.
Wiggle-test the harness and connector with the engine running while watching live data for dropouts.
Using the manufacturer's wiring diagram, test the sensor supply, signal and earth for continuity, shorts and voltage.
Measure the sensor resistance against the manufacturer's temperature specification.
Check battery condition and the power and earth supplies to the relevant modules, then check whether the network is communicating properly and whether any software updates apply to this model.

How to fix

Replace the charge air cooler outlet temperature sensor if it is out of specification.
Repair or replace the damaged wiring, or clean and repair the connector terminals.
Fix any oil, coolant or boost leaks that are contaminating the sensor or harness.
Repair power, earth or network faults affecting the module that reads the signal.
Update the control unit software only if the manufacturer identifies it as a known cause for this fault.
Replace or repair the control unit only after the wiring and sensor are fully proven good.

Can I keep driving?

Medium severity

The car can usually be driven gently for a short time, but power may be limited and the control unit is working without proper charge air temperature data. Get it fixed soon, and avoid heavy loads or sustained high boost until then.

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