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DTC codes / U02xx · Lost communication with a control module / U0297

U0297Lost Communication with Hybrid Powertrain Control Module

U0297 is a generic network communication code indicating that one or more control modules have lost the CAN (Controller Area Network) data link with the Hybrid Powertrain Control Module, which is the computer that manages the high-voltage hybrid system. The module that set the code expected to see regular status messages from the hybrid controller but stopped receiving them for a calibrated time period, so it flagged the communication failure.

SystemNetwork
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaLost communication with a control module

Symptoms you may notice

  • Illumination of the check engine light, often accompanied by a hybrid system warning or master warning lamp
  • The vehicle may enter a reduced-power or limp-home mode with limited acceleration
  • The gasoline engine may run continuously or refuse to start, depending on the hybrid system design
  • The high-voltage battery may stop charging or the electric drive may become unavailable
  • Intermittent no-start conditions where the ready indicator fails to illuminate
  • Often no symptoms besides the warning light if the lost message is not critical to current operation

Common causes, most likely first

  1. Damaged, corroded, or loose CAN bus wiring or connector terminals between the hybrid controller and the network
  2. Failed Hybrid Powertrain Control Module, including internal power or ground faults that shut the module down
  3. Blown fuse or faulty relay supplying power to the hybrid control module
  4. Poor ground connection at the hybrid controller or at a shared network ground point
  5. CAN bus network fault such as a short to ground, short to voltage, or open circuit on the data lines
  6. Another module on the same CAN segment holding the bus down and disrupting all communication
  7. Software or calibration issue in the hybrid controller that prevents it from transmitting status messages

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes in every module, then verify whether U0297 is current or history and whether other modules also report lost communication
  2. Check the battery voltage and charging system, then inspect the fuse and relay that supply power to the Hybrid Powertrain Control Module
  3. Visually inspect the CAN wiring and connectors at the hybrid controller for corrosion, pushed-out pins, chafing, or loose terminals
  4. Measure CAN bus resistance and voltage at the diagnostic connector to confirm the network is intact and not shorted or open
  5. Perform a voltage drop test on the hybrid controller power and ground circuits under load to rule out high resistance
  6. If wiring and power are good, substitute a known-good module or perform a module communication test to confirm the hybrid controller is not transmitting
  7. After repairs, clear codes and verify that the hybrid controller communicates reliably through several drive cycles before releasing the vehicle

Network faults that mimic a dead hybrid module

  • A completely dead 12-volt battery or a failing alternator can cause multiple modules to drop off the CAN bus and set U0297 even though the hybrid controller itself is healthy.
  • Corroded ground straps or a loose engine-to-body ground can interrupt the hybrid controller's reference voltage and make it appear offline to the rest of the network.
  • A single shorted module on the same CAN segment can pull the entire bus down, so U0297 is sometimes a symptom of another module's failure rather than the hybrid controller itself.
  • Some vehicles require a relearn or initialization procedure after reconnecting the hybrid controller, and skipping it can leave the code stored even when communication is restored.
  • Aftermarket accessories wired into the CAN bus or tapped into module power circuits are a frequent cause of intermittent U0297 that only appears under certain electrical loads.

Can I keep driving with U0297?

Because the Hybrid Powertrain Control Module manages high-voltage battery charging and electric drive, losing communication with it can cause a sudden loss of power or a no-start condition, so the vehicle should not be driven until the fault is diagnosed. If the car is already in limp mode, limit driving to moving it to a safe location and arrange a tow rather than attempting a normal trip.

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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