Comprehensive diagnostic guide for OBD-II code U0407

Overview

• What the code generally represents: U0407 is a universal OBD-II class U diagnostic trouble code (network/communications). It indicates that a module on the vehicle's data communication network reported invalid or unexpected data to another module (commonly the PCM/ECM or a gateway/controller). In practice, many manufacturers describe this as an invalid data condition received over the CAN (Controller Area Network) or other vehicle networks.
• Why it matters: The CAN network is the backbone for modules such as the PCM/ECM, TCM, ABS/ESC, body control modules, gateways, and other controllers. If data on the network is invalid or inconsistent, modules may misbehave or fail to respond, which can trigger U0407 and potentially other U-codes.

Symptoms and user-reported scenarios

• Check Engine Light or Malfunction Indicator Light (MIL) is ON due to U0407, often accompanied by other U-codes or P/U codes arising from module communication failures.
• Intermittent or inconsistent vehicle performance: drivability issues, limp mode or limited power, or unexpected behavior in non-engine systems (transmission, ABS, body controls) due to partial or corrupted data on the network.
• Multiple modules may be "offline" or fail to respond to scan tools; some modules may display diagnostic data that seems abnormal or inconsistent.
• In some cases, the vehicle may run normally for a period and then exhibit CAN/network-related faults after a driving cycle, battery/ignition fluctuation, or after a module replacement or software update.

Technical Context

• According to the OBD-II concept: class U codes are network communication codes. They relate to data the vehicle's control modules exchange over the vehicle communication bus(s). A U0407 specifically signals that a node on the network supplied data that the receiving module determined to be invalid or not in expected form/range. The exact "originating" module and the "receiving" module can vary by vehicle, and some makers describe it as invalid data from the PCM/ECM or from a gateway/PCM interface.
• The effect of a U0407 is generally not about a single sensor misreading (that would be a P-code). It's about data packets or messages on the network being out of spec or not understandable by the receiving module.

Probable Causes

Notes:

• do not include quantified NHTSA complaint frequencies for U0407, so the following probabilities are framed as field-experience guidance and typical risk drivers, rather than agency-based frequency data. frequencies should supersede these estimates.
• Common drivers across vehicles for CAN/network-related U-codes include wiring/connectivity faults, faulty controllers, software/firmware issues, and power/ground problems.

Probable Causes

• CAN bus wiring/connectors issue near or on the PCM or gateway: corrupted, shorted, pin misalignment, water intrusion, improper aftermarket installations; can produce intermittent invalid data on the network. 25-40%
• Faulty or intermittently failing PCM/ECU (or a gateway/multiplex module): a single node on the network that generates or misinterprets data can trigger U0407; replacement or reflash may be required. 20-35%
• Electrical power/ground reliability issues: low battery voltage, poor grounds, or charging system instability can cause modules to output or interpret data incorrectly. 10-20%
• Aftermarket devices or improper wiring: devices that draw CAN-related power or introduce noise can corrupt messages. 5-15%
• Software/firmware mismatch or corruption on one or more modules: out-of-date or corrupted code can cause incompatible data on the bus. 5-15%
• Faulty CAN bus hardware in a module or a damaged ECU interface: physical damage or a faulty transceiver can cause data framing issues. 5-15%

Note: If different sources or manufacturers describe U0407 slightly differently (e.g., "invalid data received from PCM," "invalid data received on CAN bus," or "invalid data from gateway"), accept that the root concept is invalid/unsupported data on the network between modules.

Diagnostic Approach

Safety note: Many CAN-network faults can cause erratic vehicle behavior. If a fault seems to affect drivability, traction/ABS, or steering, limit road testing and perform diagnostics in a controlled environment. Disconnect aftermarket devices if present to rule out interference.

1) Confirm symptoms and gather details

• Record all active DTCs with a capable scan tool (not all tools read U-codes equally). Note other codes that appear (P, U, B, C) and any freeze-frame data.
• Look for patterns: Do multiple modules show abnormal behavior? Does the MIL stay on or flash? Are there intermittent reboots or reset events in the cluster or infotainment system?

2) Check basic power and grounding

• Verify battery voltage is healthy (typically 12.6-14.6 V when running; ensure no significant dips during cranking or load conditions).
• Inspect grounds and battery terminals for corrosion and tightness; verify main engine harness grounds to chassis and engine are clean and secure.
• Check for parasitic draws that could destabilize bus power and cause modules to reboot or intermittently interpret data.

3) Inspect the CAN network hardware and connections

• Visually inspect CAN high (CANH) and CAN low (CANL) wires for damage, chafing, or pin damage at the PCM and main gateway/witching module connectors.
• Check for aftermarket wiring harnesses, adapters, or modules that could interfere with CAN termination or timing. Remove or isolate aftermarket devices if suspected.
• Confirm proper terminations: most controllers expect proper 120-ohm CAN terminations at each end of the bus; verify if a failed or missing termination resistor could cause network errors.

4) Review and test relevant modules and gateways

• Identify which modules are on or near the CAN network path to the PCM (gateway, body control module, ABS, TCM, instrument cluster, infotainment, etc.).
• If possible, perform a controlled 1-by-1 disconnect test of suspect modules (disconnecting a module's data line or power under safe conditions) to observe whether U0407 behavior clears or returns.
• Consider reprogramming or updating firmware on modules where a known bulletin or OEM update addresses CAN data integrity; ensure the vehicle VIN matches the module software version if applicable.

5) Analyze CAN bus activity and messages

• Use an oscilloscope or a capable CAN scanner with message-level analysis to observe CANH/CANL at idle and during bus activity.
• Look for corrupted frames,Bus-off conditions, or repeating invalid frames. Note which modules are transmitting when U0407 occurs.
• If accessible, capture a log around the time the code sets to see the sequence of messages that precede or accompany the fault.

6) Check for software/firmware issues

• Confirm there are no outstanding OEM software/firmware updates for the PCM and gateway modules.
• If a recent module replacement occurred, verify the new module is properly coded/initialized for this vehicle and that data is being correctly interpreted by the rest of the network.

7) Road test and recheck

• After performing repairs or post-repair reinitialization, clear DTCs and perform a controlled road test to reproduce the fault. If U0407 reappears, re-check network health and look for new fault codes or patterns.

8) Documentation and escalation

• If the fault remains unresolved after wiring/grounds checks and module testing, escalate to the OEM service information (TIS, WDS/ODIS, or equivalent) to verify there are no campaign/flash requirements for a given module.
• If a specific module is suspected but not easily tested in the field, consider professional-grade bench testing or module replacement with proper programming.

Repair Actions

• Fix wiring/connection issues on the CAN network; replace damaged harnesses or connectors; fix or re-route aftermarket equipment to reduce interference.
• Replace or repair faulty modules that are confirmed as the data source generating invalid messages (e.g., PCM/ECM, gateway, or a faulty transceiver).
• Perform ECU reflash or software updates per OEM guidelines if data incompatibility or firmware bugs are suspected.
• Improve power/ground reliability; address battery/charging issues; ensure solid grounds across the vehicle.
• Correct any improper terminations if found (verify 120-ohm terminators at network endpoints).
• Address aftermarket devices by removing or reconfiguring them, ensuring they do not inject noise or power on CAN lines.

Safety Considerations

• Avoid disconnecting devices or wiring while the ignition is ON to prevent data loss, short circuits, or vehicle/component damage.
• When working on CAN network harnesses, use insulated tools and avoid shorting adjacent wires.
• If the vehicle has active safety systems (e.g., ABS, stability control), ensure the vehicle is secured and test plans do not expose occupants to risk.

How this information maps to sources

• Technical basis: The concept of U-codes as network/communication issues and the idea that U0407 involves invalid data on the CAN network comes from the OBD-II overview sections in Wikipedia (Diagnostic Trouble Codes; Powertrain Codes). This provides the general framework for classifying U-codes and their origins on vehicle networks.
• General diagnostic approach and network-focused reasoning align with the broader description of how modern vehicles rely on inter-module communication for proper operation and how data integrity issues manifest as DTCs.
• For standard code definitions, GitHub repositories commonly enumerate U0407 as an invalid data/communication data issue on the CAN bus or between ECM/PCM and other modules. The diagnostic approach here reflects that network-centric interpretation.

Limitations and notes on sources

• describe general OBD-II code families and network-communication concepts but do not provide a vehicle-specific definition for U0407, nor do they supply manufacturer-specific decoding or a quantified frequency distribution of causes. When manufacturer-specific definitions or data become available, those should be used to refine this guide.

Optional references and related codes to consider

• Related network/communication codes that may accompany U0407: U0100 (lost communications with ECU), U0101/U0121 (loss of communication with ABS or other modules), U1000/U1016 (protocol or network-related issues) depending on vehicle make and year. Cross-check with a comprehensive OEM fault code directory if available.
• Aftercare: If a vehicle has a known gateway or multiplexing system, verify that the gateway software is compatible with all connected modules and that there are no VIN-specific lockouts or security features affecting data exchange.

In summary

• U0407 is a network-communication DTC indicating invalid data on the vehicle CAN network, most often involving the PCM/ECM or gateway/module nodes. A structured approach-covering power/ground, wiring and connectors, module health, firmware/software, andCAN-bus activity-typically yields the root cause. Prioritize securing clean power and grounds, validating the integrity of CAN wiring and terminations, and isolating suspect modules or aftermarket devices before replacing components. Cite: Wikipedia's OBD-II discussions for the framework of U-codes and CAN network behavior; GitHub code lists for standard definitions of U0407 as a network/invalid data issue.

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.

---