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DTC codes / U35xx · Network communication / U355A

U355ACharge Air Cooler Outlet Pressure Sensor 1 Circuit

U355A indicates that the powertrain control module has detected an electrical fault in the circuit for the charge air cooler outlet pressure sensor, which measures boost pressure after the intercooler. The computer monitors the sensor signal voltage and sets this code when the reading falls outside the expected range or is inconsistent with other pressure sensors.

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

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Reduced engine power or limp mode due to lost boost feedback
  • Poor acceleration or sluggish throttle response
  • Decreased fuel economy from incorrect air-fuel ratio calculations
  • Occasional rough idle or hesitation under load
  • In rare cases, black smoke from the exhaust if the engine runs rich

Common causes, most likely first

  1. Faulty charge air cooler outlet pressure sensor
  2. Damaged or disconnected wiring harness at the sensor connector
  3. Corroded or loose electrical terminals in the sensor circuit
  4. Failed intercooler or boost leak causing pressure readings to deviate
  5. Contaminated sensor element from oil or debris in the intake tract
  6. PCM software issue or internal fault in the pressure sensor circuit

How to diagnose and fix it

  1. Inspect the sensor connector and wiring for damage, corrosion, or loose pins
  2. Check for boost leaks or intercooler damage that could affect pressure readings
  3. Measure reference voltage and ground at the sensor connector with a multimeter
  4. Compare the sensor signal voltage with a known-good sensor or scan tool data
  5. Replace the charge air cooler outlet pressure sensor if testing confirms it is faulty
  6. Repair or replace damaged wiring and clear the code, then verify the repair with a test drive

What technicians check before replacing the sensor

  • A boost leak or cracked intercooler often mimics a sensor failure by causing pressure readings to fall outside the expected range.
  • Oil contamination from the turbocharger can coat the sensor element and skew its output without completely failing it.
  • The PCM may set U355A when another pressure sensor in the same circuit provides implausible data, so always check related sensors.
  • Intermittent wiring faults at the connector are common and can be missed if the harness is not flexed during testing.
  • Replacing the sensor without verifying reference voltage and ground can lead to a repeat failure if the circuit itself is damaged.

Can I keep driving with U355A?

You can usually drive the vehicle with this code, but avoid heavy acceleration or towing until it is repaired because the engine may enter limp mode and reduce power unexpectedly. Prolonged driving with a faulty sensor can lead to poor fuel economy and increased emissions.

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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