B1556 on Lincoln: How to Diagnose & Fix
Ignition Run/Start Circuit Open
1 Lincoln model · 1 documented issue
B1556 on Lincoln by model: symptoms, diagnosis and fix
Ford documents several distinct Aviator power-liftgate conditions. On some 2020-2022 vehicles, failure only through hands-free intelligent access or the outside handle while doors are locked can result from a poor connection at rear-keyless-entry connector C4332 below the striker (SSM 50810). Some 2020-2021 inoperative liftgates can involve RGTM software (SSM 49914). Early 2020 vehicles built on or before February 17, 2020, can partially open or trigger a false anti-theft alarm with B144D, B144E, B1555, or B1556 from RGTM software (SSM 49015). These bulletins do not diagnose every liftgate fault.
Common Symptoms
- Hands-free or outside-handle opening fails while doors are locked
- Power liftgate is inoperative
- Early-build liftgate opens only partially
- False anti-theft alarm with liftgate-ajar sensing
How to Fix
Record which inputs fail, door-lock state, build date, movement, latch behavior, warnings, and RGTM DTCs. For the SSM 50810 symptom, inspect connector C4332 for connection, terminal, and pin-fit problems. For a matching SSM 49914 or 49015 software condition, use the latest Ford diagnostic software to reprogram the RGTM. If the symptom does not match, continue Workshop Manual diagnosis of power, grounds, switches, latch, position sensing, struts, wiring, and obstruction detection before selecting a part. This record intentionally has no commerce link.
Owner tips & cautions
- TipTest each input with the doors locked and unlocked and save the RGTM scan; input-specific behavior separates connector, software, and mechanical paths.
- WarningDo not buy a latch, strut, motor, or RGTM from a generic no-open symptom; Ford's SSMs first require a specific symptom/build/DTC match.
Sources for this issue (3)
B1556 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B1556 mean on a Lincoln?
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. On Lincoln it is documented across 1 model: Aviator.
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 on a Lincoln?
Repair costs vary widely with the root cause and Lincoln model; each issue on this page carries its own estimate where one is published.
Looking for B1556 on a different make?
View B1556 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.