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DTC codes / U35xx · Network communication / U355D

U355DExpander Inlet Pressure Sensor 1 Circuit

U355D is a generic network communication code indicating that a control module has lost or received invalid data from the Expander Inlet Pressure Sensor 1 circuit. The computer detected a fault in the serial data or signal circuit that carries pressure information from this sensor, which is typically used in air suspension or central tire inflation systems to monitor inlet pressure.

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

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) or a specific suspension or tire pressure warning light.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.
  • Inability to adjust ride height or tire pressure if the system relies on this sensor for operation.
  • A default or limp mode in the suspension or inflation system, limiting vehicle speed or functionality.
  • Erratic operation of the air compressor or pressure regulation, such as frequent cycling or failure to build pressure.

Common causes, most likely first

  1. Damaged or corroded wiring harness or connector at the Expander Inlet Pressure Sensor 1.
  2. Failed Expander Inlet Pressure Sensor 1 itself, providing no signal or an out-of-range signal.
  3. Poor electrical connection at the control module that interprets the sensor data.
  4. Open or short circuit in the signal or reference voltage circuit between the sensor and the module.
  5. Water intrusion or contamination in the sensor or connector, causing signal corruption.
  6. Software or calibration issue in the control module affecting sensor data processing.

How to diagnose and fix it

  1. Perform a visual inspection of the sensor, connector, and wiring for obvious damage, corrosion, or loose pins.
  2. Use a scan tool to retrieve all stored codes and freeze-frame data, and check for related codes in other modules.
  3. Measure reference voltage and ground at the sensor connector with a digital multimeter (DMM) to verify power and ground integrity.
  4. Backprobe the signal wire and compare sensor output to expected values while manipulating the harness to check for intermittent faults.
  5. If the sensor signal is missing or incorrect, test the sensor with a known-good unit or perform a resistance check if specified.
  6. Repair or replace damaged wiring or connectors, then clear codes and verify the fault does not return.
  7. If the sensor and wiring are good, diagnose the control module or perform a software update as per manufacturer procedures.

Common misdiagnosis traps for U355D

  • A loose or corroded ground connection at the sensor or module can mimic a failed sensor, so always verify ground integrity before replacing parts.
  • Intermittent faults often occur due to harness chafing near moving suspension components, which may not be visible without wiggling the harness during testing.
  • The code can be set by a low battery or charging system issue that causes modules to communicate erratically, so check battery voltage and connections first.
  • Some vehicles use the same sensor for multiple functions, and a fault may only appear under specific conditions such as when the system is active, so test under load if possible.
  • Replacing the sensor without checking for water intrusion in the connector can lead to repeat failures if the source of moisture is not addressed.

Can I keep driving with U355D?

If the warning light is on but the vehicle drives normally, you can continue driving with caution, but avoid using the suspension or tire inflation features until repaired. If the system is in limp mode or affecting ride height or tire pressure, limit driving to low speeds and seek repair promptly to avoid unsafe handling or tire damage.

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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