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Home / DTC / U027C — Lost Communication With Off-Board Charger Control Module

U027C — Lost Communication With Off-Board Charger Control Module

Detailed page for trouble code U027C.

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Code

U027C

Generic U — Network/User

Lost Communication With Off-Board Charger Control Module

Brand: Generic
Type: U — Network/User
Views: UK: 13 EN: 28 RU: 16
AI status
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Page language: EN

Causes

  • Physical wiring harness damage between vehicle network and off-board charger control module
  • Connector corrosion, loose pins or poor terminal contact at module or gateway
  • Blown fuse or faulty relay supplying power to the off-board charger control module
  • Failed off-board charger control module
  • Faulty or improperly terminated CAN (or other network) bus segment
  • Software/configuration mismatch or corrupted module firmware

Symptoms

  • Charge function unavailable or reduced charging rate
  • Charging stops or fails to start when connected to external charger
  • Charge/EVSE warning lamps or messages on instrument cluster or infotainment
  • Related stored DTCs for CAN/network or charger subsystem
  • Intermittent charging behavior or faults only when external charger attached
  • No response from charger control module when queried with a scan tool

What to check

  • Read all network DTCs and freeze frame data; note occurrence (permanent/intermittent)
  • Check for other U-codes or network-related codes that indicate broader bus issues
  • Visually inspect connectors, wiring, and shielding for damage or corrosion at the charger module and gateway
  • Verify fuses/relays feeding the off-board charger control module are present and functional
  • Attempt to communicate with the off-board charger module with a scan tool; record any module responses
  • Check battery/vehicle accessory power and ground at the module connector

Signal parameters

  • Network type: typically CAN (vehicle-specific — verify wiring diagram)
  • Expected module heartbeat/message rate: typically periodic (0.5–10 Hz) depending on system
  • CAN bus idle voltages: each CAN line near the reference nominal (verify manufacturer values) and proper differential signaling when active
  • Power supply: module supply voltage (vehicle accessory / 12 V or low-voltage supply) present at ignition/charge enable
  • Ground continuity between module ground pin and chassis ground
  • Message IDs and payloads are vehicle-specific — capture with a CAN tool for exact parameters

Diagnostic algorithm

  1. Confirm DTC is current: clear codes, attempt charge cycle, see if U027C returns and note conditions.
  2. Scan the vehicle network for additional U-codes or module communication failures to determine scope.
  3. Inspect wiring and connectors to the off-board charger control module and related gateway for damage, corrosion, or loose pins.
  4. Verify module power and ground: check fuses/relays, probe supply and ground pins at the module connector with key/charge states as required.
  5. Check CAN/network integrity: measure voltages at module connector, verify termination resistors, and use an oscilloscope or CAN sniffer to confirm message traffic and absence of bus errors.
  6. If bus shows noise or no traffic, isolate segments by disconnecting downstream nodes (including external charger/adapter) to identify cause.
  7. If the module is not responding but has proper power/ground and bus signals, attempt a module wake/initialization per service information or re-flash software if updates are available.
  8. Test with a known-good external charger or known-good module (if available) to confirm whether the issue follows the module or stays on the vehicle wiring/network.
  9. Replace wiring/connector components only after verifying fault location. Replace the off-board charger control module only after confirming module failure and performing required programming/configuration.
  10. After repairs, clear codes and perform a complete charge cycle to verify communication and restore normal operation.

Likely causes

  • Open or short on the CAN high/low lines or lost chassis ground to module
  • Power feed (12 V/vehicle supply) or ground missing at charger control module
  • Intermittent connector contact (water intrusion, corrosion, bent pins)
  • Module is asleep, disabled by body gateway, or has failed internal transceiver
  • Incorrect or missing CAN termination resistor or damaged bus wiring after recent repairs
  • Aftermarket charger or adapter generating invalid messages on the network

Fault status

⚠️ Status
U027C — Lost Communication With Off-Board Charger Control Module (communication timeout/failure between vehicle network and off-board charger control module).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 Hours

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U0100 U0105 U0121 U0140 U0155
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