OBD-II code · Network (extended)
U3003 Battery Voltage
The control module detected battery voltage outside its acceptable operating window. Either too low (drained battery, weak charging) or too high (charging system overvoltage).
Is it safe to drive with U3003?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyBattery aged or sulfated
- PossibleAlternator regulator fault (over- or undervoltage)
- Less likelyGateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–2 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Battery, Alternator, Charging System
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.