What does it mean?
U3007 is a Network (CAN bus, module communications) fault code. It indicates: Control Module Input Power "B" . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- Part of the module's functions works while another part is dead, because only one supply is present
- Warning lamps for that system, with odd, half-working behaviour
- Module answers the scan tool but reports faults it cannot clear
- Fuse for that circuit blows again after replacement
- Functions fail as soon as the ignition is switched to a particular position
- The code sets again at every key-on
Likely causes
- Fuse for the "B" power input blown, or the wrong rating fitted
- Broken wire or an open joint between the fuse box and the module
- Corroded or backed-out terminal on the "B" supply pin at the module connector
- Relay or ignition-switched circuit that supplies this feed not energising
- High resistance in a shared power distribution point or a corroded busbar
- Wiring pinched or cut during accessory installation or interior work
- Internal module short pulling the feed down until the fuse opens
How to fix it
- Identify from the wiring information which fuse and relay serve the "B" power input
- Measure voltage at that pin with the ignition in each position; the feed must match the specification
- Do a voltage drop test under load, not just a static voltage reading
- Check continuity from the fuse box to the module connector with the circuit disconnected
- Inspect the power distribution points and busbars for corrosion and heat damage
- If the fuse keeps blowing, disconnect the module and check whether the short is in the harness or in the module
- Replace the module only after both supplies are confirmed good at its connector