U0096

Code

Generic U — Network/User

Vehicle Communication Bus H (+) High

Brand: Generic

Type: U — Network/User

Views: UK: 33 EN: 39 RU: 37

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Page language: EN

Causes

Short to battery or other power source on CAN_H
Failed or damaged module driving CAN_H high
Wiring harness damage, chafing, or pinched conductor on CAN_H
Corroded/loose connector or terminal on CAN_H
Incorrect or missing CAN termination (open or shorted resistors)
Poor or missing chassis ground or module ground

Symptoms

Loss of communication with one or more control modules (error messages or nonresponsive modules)
Multiple dash warning lights or instrument cluster errors
Systems reliant on network data may be inoperative (e.g., ABS, traction, HVAC, displays)
Intermittent or permanent fault codes related to communication (U-codes)
Possible no-crank/no-start if ECM/PCM communication lost
Erratic module behavior or random faults

What to check

Scan all modules and record U-codes and freeze frame data
Check battery voltage and charging system health
Visually inspect CAN wiring, connectors, and module pins for damage or corrosion
Measure CAN_H and CAN_L voltages with ignition ON (engine OFF) using DMM and oscilloscope
Measure resistance across bus termination (should be ~60 ohms between CAN_H and CAN_L with key off and both terminators connected)
Disconnect suspected module(s) (with ignition OFF per manufacturer guidance) to see if fault clears

Signal parameters

Normal (recessive) CAN_H voltage: ~2.5 V ±0.25 V
Normal (dominant) CAN_H voltage: ~3.5 V (during dominant bits) above CAN_L; CAN_L drops to ~1.5 V
Normal differential (CAN_H - CAN_L) dominant: ~1.5–2.5 V; recessive differential: ~0 V
Fault condition (CAN_H high): CAN_H > ~3.9–4.0 V or approaching battery voltage indicates short to power
Short-to-ground condition: CAN_H near 0 V
Termination: two 120 ohm resistors in parallel at ends -> ~60 ohm measured between CAN_H and CAN_L with ignition OFF

Diagnostic algorithm

Record all stored codes and freeze frame; note when codes set and any related events.
Verify battery voltage and charging system (low battery can cause network errors).
Visually inspect CAN bus wiring and connectors from modules that report or are affected by communication loss; look for pinched wires, damaged insulation, or corrosion.
With ignition ON (engine OFF), measure static voltages at a known good connector: CAN_H ~2.5 V (recessive). If CAN_H is >3.9 V, suspect short to power or faulty transceiver.
Use an oscilloscope to observe CAN_H and CAN_L signals while bus is active; confirm recessive/dominant behavior and look for stuck-high pulses or steady over-voltage.
Measure resistance between CAN_H and ground and between CAN_H and battery (engine off). A near-battery reading suggests short to 12 V; near 0 V suggests short to ground.
Check termination resistance between CAN_H and CAN_L (~60 ohms). If open or much higher, locate/repair open terminator or wiring break.
If a specific module is suspected, disconnect that module (follow vehicle procedures; ignition off) and clear codes; if U0096 clears, isolate that module or its harness for repair/replacement.
Inspect/repair any damaged wiring or connectors found; replace corroded terminals and reseal harness entries against moisture.
If wiring checks good and fault persists, verify module power/ground integrity. Replace or reprogram the failing module per manufacturer guidance.
After repairs, clear codes and perform road/drive cycle to confirm fault does not return and network communications are restored.

Likely causes

Short to constant 12V on CAN_H due to damaged insulation or contact with a powered wire
A single failing control module whose transceiver is stuck driving CAN_H high
Open or incorrect termination resistor(s) causing improper bus voltage
Connector corrosion allowing high-resistance connection and abnormal voltages
Aftermarket device tied to CAN_H creating an over-voltage condition