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DTC codes / U06xx · Network communication / U0626

U0626Lost Communication With A/C Refrigerant Pressure Sensor A

U0626 is a network communication code indicating that a control module on the vehicle's Controller Area Network (CAN) bus has lost contact with the A/C refrigerant pressure sensor A, which is typically wired to the climate control module or the engine control module. The computer detected that expected data messages from that sensor, or from the module that publishes its reading, stopped arriving within the required time window, so it flagged the missing communication rather than a direct sensor circuit fault.

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

Symptoms you may notice

  • The air conditioning may stop cooling or blow only warm air because the system cannot verify refrigerant pressure.
  • The A/C compressor clutch may fail to engage, or it may cycle rapidly and unpredictably.
  • A yellow or red warning light on the dashboard, often accompanied by a message such as 'A/C system service required'.
  • The climate control panel may show erratic blower behavior or default to a fixed temperature setting.
  • Often no symptoms besides the warning light, especially if the vehicle's climate system has a fail-safe default mode.
  • Other unrelated electrical accessories may act up if the lost communication is part of a broader bus fault.

Common causes, most likely first

  1. A failed A/C refrigerant pressure sensor A, which stops transmitting its pressure reading onto the network.
  2. Damaged, corroded, or disconnected wiring and connectors between the sensor and the module that publishes its data.
  3. A faulty climate control module or engine control module that is not broadcasting the sensor data onto the CAN bus.
  4. Low or contaminated refrigerant charge causing the sensor to read outside its expected range and the module to reject its message.
  5. A shorted or open CAN bus data line that isolates the module responsible for the sensor signal.
  6. A blown fuse or poor ground that removes power from the sensor or its host module.
  7. Software or calibration issues in a module that intermittently drops the sensor message under certain conditions.

How to diagnose and fix it

  1. Connect a scan tool and read all stored codes in every module, then record freeze-frame data for U0626 to see when the communication loss occurred.
  2. Inspect the A/C refrigerant pressure sensor connector and the harness for corrosion, chafing, or loose pins, and verify that the sensor receives reference voltage and ground.
  3. Check the refrigerant charge with a manifold gauge set or a recovery machine to confirm the system is neither empty nor overcharged.
  4. Perform a network integrity test or a CAN bus voltage check to rule out a shorted or open data line that would affect multiple modules.
  5. Substitute a known-good A/C refrigerant pressure sensor A and clear the code to see whether communication returns.
  6. If the sensor and wiring test good, check for software updates or reflash the climate control module or engine control module as applicable.
  7. Clear all codes after the repair and road-test the vehicle with the A/C on to confirm that U0626 does not reset.

What the pressure sensor code hides

  • U0626 is a communication code, not a direct sensor performance code, so replacing the pressure sensor without checking the network can leave the fault unchanged.
  • A low refrigerant charge is a frequent hidden cause because the sensor reports a pressure outside the expected range and the module may discard the message as invalid.
  • Some vehicles publish the A/C pressure reading through the engine control module rather than the climate panel, so a fault in either module can set this code.
  • Intermittent U0626 codes often trace to a chafed harness near the compressor or a corroded ground shared with other engine bay sensors.
  • A scan tool that only reads powertrain codes may miss U0626 entirely because it can be stored in a body or climate control module.

Can I keep driving with U0626?

You can usually drive the vehicle with U0626 stored, but avoid relying on the air conditioning and do not ignore repeated warning lights. Have the fault diagnosed soon, because a communication loss that spreads to other modules can affect engine cooling fans or other systems that share the same network.

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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