Loose, corroded or damaged connector at the module power supply or earth pins; Poor battery terminal or earth strap connection, or corrosion; Open circuit or chafed wiring in the module's B power feed, intermittent due to vibration or movement; Weak or failing battery, or a charging system giving unstable voltage; Faulty fuse, fuse holder, relay or power distribution box contact supplying that circuit; Internal fault in the control module affecting its power input.

U3507

Control Module Input Power B Circuit Intermittent/Erratic.

Generic
Network
Generic code
Medium severity

How this code is built

U: SystemNetwork
3: Defined bySAE, the same on every car
5: AreaNetwork area 5
07: FaultThe specific fault in that area

What it means

U3507 means a control module has detected that its 'B' input power supply circuit is intermittent or erratic. The module saw its supply voltage drop out, fluctuate or arrive unstably when it should have been steady. The code does not say which module logged it, and which supply is 'B' depends on the vehicle, so the wiring diagram is needed.

Symptoms

Warning lights on the dashboard, possibly more than one system
Intermittent loss of function in the affected system, which may be engine, transmission, body or other
Engine hard starting, cutting out or stalling at random
Other modules logging communication or low voltage codes
Faults that appear over bumps, in wet weather or when wiring is moved
Dim, flickering or resetting instruments

Possible causes

Loose, corroded or damaged connector at the module power supply or earth pinslikely
Poor battery terminal or earth strap connection, or corrosionlikely
Open circuit or chafed wiring in the module's B power feed, intermittent due to vibration or movementlikely
Weak or failing battery, or a charging system giving unstable voltagepossible
Faulty fuse, fuse holder, relay or power distribution box contact supplying that circuitpossible
Internal fault in the control module affecting its power inputrare

How to diagnose

Read all stored codes and freeze frame data, noting which module set U3507, whether other modules have power or communication codes, and whether the fault is current or historic
Check battery condition and state of charge, and test charging voltage with the engine running
Inspect battery terminals, main earth straps and engine-to-body earths for looseness and corrosion
Find the module's B power supply circuit, fuse and relay in the manufacturer wiring diagram, as this varies by model and engine
Inspect the fuse, fuse holder and relay contacts for heat marks, looseness or corrosion
Check the module connector for bent, pushed-back or corroded pins and signs of water ingress
With a multimeter on the supply and earth pins, wiggle test the harness while watching for voltage drops or dropouts
Do a voltage drop test under load on the supply and earth paths, and only suspect the module once wiring and supply are proven good

How to fix

Clean and tighten battery terminals and earth connections, and replace any damaged straps or terminals
Repair or replace damaged wiring and connectors in the B power circuit, using proper crimps or sealed joints
Replace faulty fuses, fuse holders or relays, and find out why they failed
Replace a weak battery or repair the charging system if voltage is unstable
Replace or repair the control module only if supply and earth are proven good and the fault persists, then perform any coding or programming it needs

Can I keep driving?

Medium severity

The car can usually be driven short-term, but the power loss may recur without warning and affect the system the module controls. Get it checked soon, and avoid driving if it stalls, loses power or shows safety system warnings.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.