U027A

Code

Generic U — Network/User

Lost Communication With Battery Charger Control Module C

Brand: Generic

Type: U — Network/User

Views: UK: 25 EN: 28 RU: 22

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Page language: EN

CAN idle (recessive) voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (vehicle-dependent)
CAN dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V; differential ≈ 2 V
Typical bus termination: ~60 Ω measured between CAN_H and CAN_L (two 120 Ω in parallel)
Common CAN data rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific)
Module supply voltage: battery voltage present at module power terminal (approx. 12 V)
Ground circuit: near 0 V with good continuity to chassis

Connect a scan tool that can display network modules; record all active and stored U-codes and freeze frame data.
Verify battery state and recharge if low. Low battery can prevent modules from waking.
Clear the code and attempt to communicate with the charger module. If code returns, proceed with wiring/communication checks.
Inspect fuses and power/ground at the battery charger control module connector. Repair any open circuits.
Visually inspect connectors and harness from module to gateway for damage or corrosion. Repair or secure connectors as needed.
Backprobe module power and ground with key ON; verify correct voltages and good ground.
With key ON, measure CAN_H and CAN_L at the module connector and at a known-good module location. Compare voltages and look for lack of activity or incorrect levels.
Measure termination resistance across CAN_H–CAN_L with battery disconnected; expect ~60 Ω. If open or very low, trace and repair the bus.
Use a scope or high-speed CAN tester to check for correct differential waveforms and noise; isolate sections of the bus to find a shorted or noisy segment.
If wiring and bus are good but communication still lost, swap or bench-test the battery charger control module if a known-good unit is available. Reprogram or update module software if required by manufacturer.
After repair or replacement, clear codes, verify communication restored, and perform charging system function test and road test as required.

Connector corrosion or pin damage at the charger control module
Open/short in CAN_H or CAN_L between module and gateway
Blown fuse or removed battery supply to the charger control module
Faulty battery charger control module hardware or failed MCU
Improper termination (missing 120 Ω resistors) or low battery voltage preventing module wake