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DTC codes / U30xx · Network wiring and bus faults / U3006

U3006Control Module Input Power A Circuit/Open

U3006 is a generic body/network code indicating that a control module has detected an open or missing voltage on its primary power input circuit, typically the 'A' or main feed. The module is reporting that it is not receiving the expected battery voltage on that dedicated power wire, which can prevent the module from operating or communicating.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaNetwork wiring and bus faults

Symptoms you may notice

  • Illumination of the check engine light or a module-specific warning lamp
  • The affected module may be completely inoperative, causing features like windows, seats, or lighting to fail
  • Intermittent operation of the module or related systems, especially over bumps or in wet conditions
  • No communication with the module when a scan tool attempts to read codes from that network
  • Often no symptoms besides the warning light if the open is on a redundant power feed
  • Multiple unrelated warning lights if the module is a gateway or body control module

Common causes, most likely first

  1. Blown fuse or tripped circuit breaker supplying the module's A power circuit
  2. Corroded, loose, or disconnected battery terminal or ground connection at the module
  3. Damaged wiring harness (open circuit) between the power distribution point and the module
  4. Faulty ignition switch or power relay that feeds the module's A circuit
  5. Water intrusion or corrosion in a connector on the power feed circuit
  6. Internal failure of the control module's power supply circuitry
  7. Aftermarket accessory improperly tapped into the power feed, causing an open or high resistance

How to diagnose and fix it

  1. Verify the code with a scan tool and check for communication with the affected module
  2. Inspect and test the fuse and relay for the module's A power circuit, replacing as needed
  3. Perform a voltage drop test on the power wire from the battery to the module connector
  4. Check and clean the module's ground connections and battery terminals
  5. Disconnect the module and inspect the connector pins for corrosion, damage, or push-out
  6. If power and ground are good at the connector, suspect an internal module fault and test with a known-good unit
  7. Repair any damaged wiring or connectors and clear the code to confirm the fix

What a U3006 often hides

  • A U3006 can be set by a module that has two power feeds; the 'A' circuit may be a backup, so the module still works and the driver notices nothing until the main feed fails.
  • Many technicians replace the module only to find a corroded fuse box terminal or a chafed wire in the loom, so always load-test the circuit under load rather than just checking for voltage.
  • This code is common after jump-starting or battery replacement if the memory saver was not used, because voltage spikes can open a fusible link in the power feed.
  • On some vehicles, U3006 is stored in a module that is not the one with the fault; the code may be a network message from another module reporting its own power loss.
  • A faulty ignition switch or main relay can cause intermittent U3006 that only appears when the vehicle is warm or after hitting a bump, so wiggle-test the harness while monitoring live data.

Can I keep driving with U3006?

If the affected module controls safety systems like airbags or stability control, do not drive until repaired. If it is a comfort or body module, the vehicle may be drivable but avoid relying on the inoperative features and have it checked soon.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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