U0080

Code

Generic U — Network/User

Vehicle Communication Bus F

Brand: Generic

Type: U — Network/User

Views: UK: 23 EN: 43 RU: 26

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Page language: EN

Causes

Open, short, or high resistance in the bus wiring or connectors
Failed or intermittently failing module attached to Bus F
Missing or incorrect termination resistors
Power or ground fault on one or more modules on Bus F
Corroded or loose connectors or pin damage
Damaged shielding or vehicle body chafing causing intermittent faults

Symptoms

One or more systems related to Bus F not functioning or intermittent operation
Multiple related control modules show 'no communication' or error codes
Illuminated warning lamp (e.g., MIL, ABS, SRS, body warning) depending on affected modules
No live messages from expected modules on scan tool for Bus F
Intermittent or permanent faults that appear or clear with movement or temperature change

What to check

Connect a full-feature scan tool and confirm U0080 and any related codes; note which modules report communication loss
Verify bus name/physical location for 'Bus F' from wiring diagrams and module network map
Visually inspect connectors, wiring harness, and grounds for damage, corrosion, pin pushed out or moisture
Check module 12V/IGN power and battery ground voltages at each module on Bus F
Measure DC resistance across bus high and low (expected ~60 ohms for CAN with two 120Ω terminators in parallel) or consult manufacturer spec
Measure voltage of CAN_H and CAN_L with key on/engine off and with bus active using DVM and oscilloscope

Signal parameters

CAN idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both near mid-rail)
CAN dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V)
Typical bus differential voltage when active ≈ 2 V
Expected bus termination resistance ≈ 60 Ω (two 120 Ω terminators in parallel) — verify manufacturer spec
LIN or single-wire buses: idle near battery voltage through pull-up, dominant near ground (verify bus type before measuring)

Diagnostic algorithm

Retrieve freeze frame and all codes; record which modules are responsive on Bus F.
Consult wiring diagrams/network map to locate Bus F wiring, terminators, and connected modules.
With battery and ignition ON, use a scan tool to monitor bus traffic. Note whether traffic is absent, constant dominant, or erratic.
Visually inspect harness sections and connectors for obvious damage where the wiring runs. Repair any damage found.
Check power and ground at each module on Bus F. Repair poor power/ground before proceeding.
Measure DC resistance between CAN_H and CAN_L with ignition OFF — compare to expected (~60 Ω for CAN). If open or much lower/higher, isolate between segments to find fault.
Use a lab scope to view H and L waveforms while exercising the bus (turning systems on, using scan tool commands). Look for stuck dominant, missing edges, reflections, or excessive noise.
If a module is suspected, disconnect modules one at a time (with ignition off unless manufacturer advises otherwise) to see if the fault clears; keep safety in mind and avoid disconnecting critical modules while driving.
Check for intermittent faults by wiggling harnesses and connectors while monitoring live data or scope traces.
Inspect/replace termination resistors if out of spec. Repair or replace damaged wiring or connectors. After repairs, clear codes and verify normal bus communication over a test drive/cycle.
If wiring and terminators are good, update or reprogram module software as required by manufacturer and consider module replacement only after isolating it as cause.

Likely causes

Damaged wiring or connector on CAN/LIN bus (physical break, short to ground/battery)
Failed module that pulls the bus to dominant state
Loss of module power or ground causing it to stop communicating
Missing/failed termination resistors (incorrect bus impedance)
Intermittent connector contact due to corrosion or vibration