B1556 on 2020-2022 Lincoln Aviator — Ignition Run/Start Circuit Open
1 vehicles · 1 makes
Most Reported On
B1556 is an OBD-II diagnostic trouble code meaning “Ignition Run/Start Circuit Open.” A body code most commonly documented on Ford-family vehicles. A module monitoring the ignition switch circuits detected an open in the run/start feed - it is not seeing power on the circuit that should be hot with the key in RUN and START. Symptoms range from no-crank or intermittent stalling to accessories and modules dropping offline, and the code can also store simply because a module was powered up outside normal ignition conditions. Related codes in the same family cover the run and accessory feeds separately (for example B1555 for a run/start circuit failure and B1356 for an open ignition run circuit), so read the exact code text rather than assuming. Because B1556 is in the manufacturer-specific body range, confirm the definition for your make before diagnosing. This code is most commonly reported on 2020-2022 Lincoln Aviator.
Common Causes
Diagnostic Tools
B1556 does not use the standard P/B/C/U prefix. It may be a manufacturer-specific code, so verify that a scanner supports your exact year, model and module before buying.
FAQ
What does B1556 mean?
B1556 stands for "Ignition Run/Start Circuit Open." A body code most commonly documented on Ford-family vehicles. A module monitoring the ignition switch circuits detected an open in the run/start feed - it is not seeing power on the circuit that should be hot with the key in RUN and START. Symptoms range from no-crank or intermittent stalling to accessories and modules dropping offline, and the code can also store simply because a module was powered up outside normal ignition conditions. Related codes in the same family cover the run and accessory feeds separately (for example B1555 for a run/start circuit failure and B1356 for an open ignition run circuit), so read the exact code text rather than assuming. Because B1556 is in the manufacturer-specific body range, confirm the definition for your make before diagnosing.
What are the most common causes of B1556?
The most common causes of B1556 are: Blown fuse on the ignition run/start circuit, Failed or worn ignition switch (electrical portion), Damaged, chafed, or corroded wiring in the run/start circuit, Loose or corroded connector at the affected module or fuse box, Faulty ignition or starter relay, Poor ground at the monitoring module. The specific cause varies by vehicle.
How much does it cost to fix B1556?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by B1556?
Au7o has documented B1556 across 1 vehicle models from 1 manufacturers: Lincoln.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.