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DTC codes / U35xx · Network communication / U355C

U355CCharge Air Cooler Outlet Temperature Sensor Circuit

U355C is a generic network communication code indicating that a control module has lost or received invalid data from the charge air cooler outlet temperature sensor circuit. The computer detects this when the sensor signal is out of range, intermittent, or missing entirely on the communication bus, preventing the powertrain control module from accurately monitoring the temperature of the air leaving the charge air cooler.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaNetwork communication

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message on the dashboard
  • Reduced engine power or limp mode due to the powertrain control module substituting a default temperature value
  • Poor fuel economy or increased turbo lag because the engine cannot optimize charge air density
  • Intermittent rough running or hesitation under acceleration if the sensor signal drops out
  • Often no symptoms besides the warning light, especially if the fault is a brief communication glitch

Common causes, most likely first

  1. Faulty charge air cooler outlet temperature sensor or its internal thermistor
  2. Damaged, corroded, or disconnected wiring or connector at the sensor or between the sensor and the control module
  3. Open or short circuit in the sensor signal or ground circuit
  4. Failed control module that cannot process or transmit the sensor data correctly
  5. Software or calibration issue in the control module causing false communication errors
  6. Water intrusion or physical damage to the sensor or connector from road debris or engine bay conditions

How to diagnose and fix it

  1. Use an OBD-II scan tool to read all stored codes and freeze-frame data, then verify the charge air cooler outlet temperature sensor reading with the key on and engine off.
  2. Visually inspect the sensor, its connector, and the wiring harness for chafing, corrosion, or loose pins, and repair any obvious damage.
  3. Measure the sensor resistance with a multimeter and compare it to the manufacturer's temperature-resistance chart to confirm the sensor is within specification.
  4. Back-probe the sensor connector to check for reference voltage and ground integrity, and test the signal circuit for continuity and shorts to ground or power.
  5. If the wiring and sensor test good, check for communication bus faults between the sensor and the control module using a factory scan tool or oscilloscope.
  6. Replace the charge air cooler outlet temperature sensor if it fails electrical testing, then clear the codes and verify the repair with a road test.
  7. If the fault persists after sensor and wiring repairs, reprogram or replace the control module according to the manufacturer's diagnostic procedures.

Don't overlook the charge air cooler sensor

  • A loose or corroded connector at the charge air cooler outlet temperature sensor is a frequent cause of U355C that many technicians miss when they focus only on the sensor itself.
  • The code can set intermittently from a brief communication dropout, so a single occurrence may not indicate a hard failure and should be cleared and monitored before replacing parts.
  • Charge air cooler outlet temperature sensor faults often accompany boost pressure or intake air temperature codes, so always check for related codes that point to a shared circuit or connector.
  • Some vehicles use the charge air cooler outlet temperature sensor as part of a combined sensor assembly, and replacing only the temperature element may not be possible or cost-effective.
  • A failing control module can set U355C without any sensor or wiring fault, so module software updates or replacement should be considered only after all circuit tests pass.

Can I keep driving with U355C?

You can usually drive the vehicle with U355C, but avoid heavy acceleration or towing because the engine may be running on a default temperature value that reduces performance and fuel efficiency. Have the fault diagnosed soon to prevent potential damage to the turbocharger or charge air cooler system.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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