U1605

Code

Generic U — Network/User

Invalid/Corrupted Vehicle Network Data

Brand: Generic

Type: U — Network/User

Views: UK: 10 EN: 18 RU: 15

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Intermittent or damaged wiring/connectors on the vehicle network (CAN bus) or module harness
Faulty module sending corrupt messages (bad transceiver, CPU, or firmware)
Improper or missing termination (open or wrong value resistor)
Low or unstable battery/charging system voltage during communication
EMI/RFI interference or short to other circuits
Software mismatch, incomplete reflash, or corrupted module firmware

Malfunction indicator lamp or communication-related warning lights
Loss or intermittent loss of function of one or more modules (e.g., instrument cluster, ABS, transmission)
Multiple communication-related DTCs stored (U-codes and P-codes)
Reduced system performance or limp-home mode for affected systems
Inconsistent or garbled data displayed on instruments or diagnostic tool

Verify stored DTCs and freeze-frame data with a scan tool; note which modules report the fault
Check battery voltage and charging system (should be ~12.4–12.8 V at rest, ~13.5–14.8 V running)
Visually inspect CAN wiring, connectors, and grounds for damage, corrosion, or looseness
Measure CAN bus idle voltages: CAN_H and CAN_L should be about 2.5 V (recessive state)
Measure dominant state: CAN_H ~3.5 V and CAN_L ~1.5 V during communication (use a scope if available)
Check termination resistance across CAN_H and CAN_L (approx. 60 ohms if two 120 ohm terminators present)

CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive)
CAN dominant voltages (during recessive->dominant): CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
Typical CAN differential voltage when dominant ≈ 2.0 V
Termination resistance (two 120 Ω terminators in parallel) ≈ 60 Ω between CAN_H and CAN_L
Common CAN bit rates: 125 kb/s, 250 kb/s, 500 kb/s — confirm vehicle-specific bitrate before capture
Acceptable error frame rate: near zero; repeated error frames or bus-off counters indicate problem

Connect a capable scan tool and record all U- and P-codes, freeze-frame data, and module communication status.
Check battery state-of-charge and charging system; restore normal voltage if low and clear codes to retest.
Visually inspect connectors, splice points, and harness routing for damage, corrosion, or rodent chew; repair as needed.
Check and secure all chassis and engine grounds that serve communication modules.
Measure termination resistance across CAN_H and CAN_L; if open or wrong value, locate and repair missing terminator.
With ignition on, measure CAN_H and CAN_L idle voltages at multiple modules to find node(s) with abnormal levels.
Use an oscilloscope to capture CAN waveforms while exercising functions; look for noise, clipped waveforms, missing edges, or constant dominant bits.
If a suspect module is identified, disconnect that module’s CAN connector and observe whether the U1605 code or bus errors clear (may require clearing codes and cycling ignition).
Update or reflash module software if a software mismatch or known issue exists; follow manufacturer procedures.
If a module’s transceiver is confirmed faulty via bench or replacement testing, replace the module or transceiver per service manual.
After repairs, clear codes, perform functional tests, and road test to ensure the fault does not recur.
Safety note: follow manufacturer procedures for module replacement and programming; avoid shorting CAN lines and protect against static when handling electronic modules.

Loose or corroded connector at a control module or splice
Failed CAN transceiver on a module (module generating invalid frames)
Broken or chafed CAN_H or CAN_L wiring (intermittent short to ground or battery)
Missing/failed termination resistor (approx. 60 ohm across CAN_H and CAN_L)
Low battery or unstable supply to one or more modules