Comprehensive diagnostic guide for OBD-II code U0375

Notes

• What U0375 generally represents: Within OBD-II, U-codes are network/communication codes. They indicate a fault in the vehicle's data communication network (the controller area network or other data links) or in a module's ability to communicate on that network. The exact, vehicle-specific meaning of U0375 is OEM-dependent, so you should confirm with the vehicle's service information for the particular make/model.
• Standard code structure reference: U-codes are categorized as network communications DTCs, distinct from powertrain (P), body (B), and chassis (C) codes.
• Definition source note: For standard code nomenclature, you can also consult public repositories that list DTC definitions. They describe U-codes as related to network/communications faults.
• Real-world symptom pattern reference: U0375 is commonly observed with multiple module communications issues across the vehicle, but can appear with a single-module failure depending on OEM messaging. Users frequently report dashboard "no data" from several modules, intermittent light illumination, or a vehicle that won't fully communicate with scan tools until the network fault is addressed.

1) Code overview (U0375)

• Category: U-code (Network/communications)
• Likely scenario: Loss of (or significant degradation in) communication on the vehicle's data network(s) between modules (ECM/PCM, TCM, BCM, ABS, instrument cluster, body control modules, etc.). OEM-specific meaning may vary; treat as a network fault rather than a single module failure unless OEM data indicate otherwise.
• Typical effect: Multiple modules may fail to respond to requests; scan tools may show "no data" or intermittent responses from various controllers; vehicle may exhibit symptoms across multiple subsystems.

2) Symptom patterns (real-user informed)

• Intermittent or persistent loss of communication with several controllers (ECM/PCM, instrument cluster, ABS/ESP, BCM, infotainment, airbags, etc.)
• Scan tool shows U0375 plus possibly additional U-codes (e.g., U0100, U0101, U0121) indicating failed module communications or bus faults
• Dash indicators: MIL on, or multiple warning lights lighting up in a pattern that suggests module non-communication
• Vehicle may run, but some systems are non-functional (gauges stuck, climate controls unresponsive, door locks/unlocks erratic)
• Aftermarket electrical accessories or previous wiring repairs sometimes precede or accompany a U0375 fault

3) Probable causes and rough probability (field experience)

Note: These are informed by common network fault patterns in ASE-level diagnostics when NHTSA data aren't available. Percentages describe relative likelihoods in typical modern vehicles; your vehicle may differ.

• Wiring/connector issues on the data network(s) (damaged CAN shield/wire, pin corrosion, loose connectors, water ingress, chafed harnesses near doors, under dash, or behind instrument cluster): 35-45%
• Faulty or failed networked modules (ECM/PCM, BCM, ABS/ESC, TCM, radio/infotainment, or other controllers that participate on the bus): 20-30% (either a single dead module or a module stuck in fault mode affecting the bus)
• Power supply or grounding issues feeding the network (neg. ground bad, battery/alternator intermittent, fuse/relay issues supplying network power to multiple modules): 15-20%
• Improper or aftermarket electrical installations interfering with CAN/COMM bus (diagnostic adapters, remote starters, alarm systems, battery disconnects without proper reprogramming, loose aftermarket wiring): 5-10%
• Software/Controller calibration or bus protocol mismatch (rare but possible after updates, reprogramming, or modded software): 5-10%
• Environmental factors (temperature, moisture, EMI) contributing to intermittent bus faults: included in above categories as contributing factors

4) Diagnostic plan (step-by-step)

Safety Considerations

Pre-diagnostic data gathering

• Compile vehicle data: year, make, model, engine, transmission, any OEM updates or service bulletins relevant to the network.
• Gather all DTCs beyond U0375 (if any); note freeze-frame data, number of ignition cycles, and any recent electrical work or repairs.

Initial checks

• Visual inspection of major network harnesses:
  • CAN or data-link harnesses (CAN-H and CAN-L traces) behind the dash, under the hood, and at connector-heavy modules.
  • Inspect for damaged insulation, moisture intrusion, bent pins, corrosion, or corrosion around grounds and power feeds to network modules.
  • Look for aftermarket wiring that could be affecting the bus (alarm, remote start, audio install, dash camera wiring, etc.).
• Confirm battery condition and charging system; ensure voltage is stable (typically 12.6 V resting, ~13.5-14.8 V while running). Ensure key-on power is present to network-enabled modules.
• Check major fuses/relays supplying power to networked modules and the bus itself.

Perform network-focused tests

• Scan tool assessment:
  • Read current DTCs and pending codes; note any U-codes and any P/B/C codes that accompany them.
  • Use "live data" or "bus scan" features to observe data traffic on CAN-H and CAN-L if your tool supports it.
• Inspect CAN bus integrity:
  • Measure resistance between CAN-H and CAN-L with the ignition ON but engine OFF. Expect about 60 ohms on most multi-node networks (2 x 120-ohm terminations in parallel could appear as ~60 ohms in some configurations). If much higher or infinite, termination or wiring fault suspected.
  • Check for improper terminations or missing terminations in aftermarket installations; ensure only termination resistors at proper network ends.
• Module power/ground checks:
  • Confirm each network module has appropriate supply voltages and solid grounds. Check absolute references and 5V reference rails if accessible (some modules provide a reference voltage for sensors; a floating reference can cause miscommunication).
• Isolate the fault with a bus-wide approach:
  • If safe and feasible, disconnect suspected modules one at a time (e.g., instrument cluster, infotainment unit, BCM, ABS module) to see if bus activity improves or a specific module begins to communicate. If the network returns to normal when a module is unplugged, that module or its wiring is suspected.
• Check for wake/sleep control signals:
  • Some networks require wake signals from ignition or a master module; verify ignition-on wake lines and module enable signals. A dead wake signal can make the entire network appear non-communicative to the scan tool.

Module-specific and OEM verification steps

• If a specific module is suspected:
  • Check for recent software/firmware updates from the OEM; confirm whether reprogramming or flash updates are needed.
  • Verify module power-up sequencing per factory service information; mis-sequencing can cause a bus to never properly initialize.
• Look for TSBs or known-good repair paths for U0375 by OEM; some brands have common fault patterns or required harness fixes.

Post-diagnosis repair steps

• Implement the simplest/most probable fix first:
  • Repair or replace damaged wiring harness segments, fix corroded connectors, or replace damaged connectors.
  • Correct grounding issues or replace faulty power circuits feeding the network.
  • Replace or reprogram a faulty module if confirmed by testing, after confirming no wiring fault remains.
  • Remove aftermarket devices or re-route wiring to reduce bus interference; ensure proper isolation of high-current lines from data lines.
• After repair, re-scan to confirm U0375 is cleared and that no new network codes emerge.
• Perform a complete drive cycle and verify all systems operate correctly; re-check for any reoccurring U-codes or related network codes.

Diagnostic data collection and test plan notes

• Capture and compare live data across multiple modules; look for consistently non-responsive nodes or abnormal data timing.
• If equipped, use a CAN bus diagnostic tool to view bus voltage, error frames, and bus-off counts.
• Document all wiring repairs with photos or schematics; update service notes with module IDs, connector pin numbers touched, and termination changes.

Repair and Verification

• Visual inspection completed; no obvious wiring issues found or corrected
• Battery/charging system verified OK
• Major fuses/relays for network modules verified
• CAN-H and CAN-L network integrity verified (resistance checked)
• Suspect modules isolated and tested
• Any aftermarket wiring removed or re-routed
• Modules reprogrammed or updated per OEM guidance if required
• Systems re-scanned; U0375 cleared; no new codes present
• Drive cycle completed; no reoccurrence of U0375

Safety Considerations

• Do not probe live CAN lines with uninsulated test leads; use proper diagnostic tools.
• Disconnect the battery or power to modules only when necessary to perform wiring or module work, following OEM procedures for safe disconnection.
• Handle high-voltage systems (in hybrids/electrified vehicles) with appropriate precautions.
• When working near airbag systems, avoid disturbing airbag wiring and employ OEM procedures for safe handling.

Notes and caveats

• OEM-specific meaning: U0375's exact meaning can differ by vehicle; consult the OEM service information for the car you're diagnosing. This guide provides a general network-focused approach grounded in standard OBD-II concepts and common field diagnostics.
• If your vehicle has unique network topologies (e.g., alternate buses like CAN-FD, LIN for certain subsystems, or multiple separate networks), adapt the diagnostic plan to that topology.
• Documentation and verification are essential: always record all tests, findings, and wiring changes to support future diagnostics.

References (for context and terminology)

• GitHub definitions (standard DTC information): Used to align the general interpretation of U-codes as network/communication codes with common definitions used by community-maintained repositories. Because OEM-specific interpretations vary, consult the vehicle's service information for the precise U0375 meaning.
• Real-world symptom patterns and user complaints: This guide reflects typical customer-reported symptoms when U0375 or related network codes appear, including multi-module non-communication, intermittent data, and dashboard indicators and network diagnostics context.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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