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DTC codes / U05xx · Network communication / U05AA

U05AAInvalid Data Received From Charge Air Cooler Coolant Pump

U05AA is a generic communication fault indicating the engine control module (ECM) or powertrain control module (PCM) received invalid or corrupted data from the charge air cooler coolant pump over the vehicle's controller area network (CAN) bus. The computer detected a message from the pump module that failed its internal plausibility or checksum validation, so it cannot trust the pump's reported status.

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, often with no other symptoms besides the warning light
  • Reduced engine power or limp mode triggered as a protective strategy when the pump's data is deemed unreliable
  • Intermittent cooling fan operation or unusual fan noise as the ECM loses confidence in the charge air cooler pump's feedback
  • Elevated intake air temperatures on the scan tool data stream, though the driver may not feel a difference in normal driving
  • Possible rough running or hesitation under sustained boost if the pump is not circulating coolant and intake temperatures climb
  • A stored history of communication-related codes in other modules, suggesting a shared bus or power supply issue

Common causes, most likely first

  1. Corroded, loose, or water-intruded electrical connector at the charge air cooler coolant pump
  2. Damaged or chafed wiring in the pump's power, ground, or CAN bus circuit
  3. Failed charge air cooler coolant pump control module or internal pump electronics
  4. Low or contaminated coolant causing the pump to overheat and report implausible data
  5. Voltage supply issues such as a weak battery or poor ground connection affecting the pump module's communication
  6. CAN bus network faults, including a shorted or open data line shared with other modules
  7. Software or calibration issues in the pump module or ECM requiring a reflash or update

How to diagnose and fix it

  1. Connect a scan tool and record all stored and pending codes in every module, then verify the U05AA is current and not a stale history code
  2. Inspect the charge air cooler coolant pump connector and harness for corrosion, loose pins, or water intrusion, and clean or repair as needed
  3. Check the pump's power and ground circuits with a multimeter under load to confirm the module is receiving proper voltage
  4. Measure the CAN bus voltages at the pump connector to rule out a shorted or open data line before condemning the pump
  5. Verify coolant level and condition, and confirm the pump runs when commanded by the scan tool using an active test
  6. If communication is present but data is invalid, check for technical service bulletins or software updates for the pump module or ECM
  7. Replace the charge air cooler coolant pump only after electrical and network checks pass, then clear codes and verify the repair with a road test

What invalid pump data really means

  • The code does not mean the pump has failed outright; it means the pump's module sent a message the ECM could not validate, which often traces to a wiring or voltage problem rather than the pump itself.
  • A weak or failing battery can cause this code on vehicles with smart charging systems because the pump module may boot up and report invalid data during low-voltage cranking events.
  • Technicians commonly replace the charge air cooler coolant pump only to find the real fault is a chafed CAN bus wire near the pump mounting bracket or a corroded ground stud.
  • Because the charge air cooler pump shares the CAN bus with other modules, a fault elsewhere on the network can corrupt messages and set U05AA alongside communication codes in unrelated systems.
  • After any repair, the ECM may need a drive cycle with several key-on cycles before it will clear the code and restore full boost control, so do not assume the fix failed if the light stays on briefly.

Can I keep driving with U05AA?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy throttle or sustained boost because the charge air cooler pump may not be circulating coolant and intake temperatures could rise. If the engine enters limp mode or you notice overheating or power loss, stop driving and have the vehicle towed.

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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