U300AIgnition Switch
- Generic OBD-II code · Network
- How the car detects it
- U300A is a module's complaint about the ignition switch as a whole: the position or key information it receives does not add up, so it cannot be sure whether the driver wants off, accessory, run or start. The failure-type byte narrows it down. Ford's SSM 52606 covers 2023–2024 Super Duty trucks with a keyed ignition that display Vehicle May Not Start/Restart Service Now with U300A:01 stored by the body control module; a grommet around the lock cylinder had shifted and hindered the key, and reseating it is the repair. On Ram's 2025 heavy-duty pickups the LED headlamps, i.e. smart lamp modules left and right, log U300A-29, signal invalid, as the key moves from run to start. Ram says to leave it alone if it only comes back as stored, but to check the hardwired ignition line if it is active 10 s after start.
- What you may notice
- Start or restart warning in the cluster, possibly a no-start
- Stored code in a lamp or body module with no noticeable effect
- Key turns stiffly or does not reach every position cleanly
- Likely causes
- PossibleKey travel hindered at the lock cylinder, e.g. by a displaced grommet or trim
- PossibleModule software that flags the run-to-start transition as invalid
- PossibleWorn or dirty contacts inside the ignition switch
- RareOpen, chafed or corroded hardwired ignition line or connector
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.