B1555 on Lincoln: How to Diagnose & Fix
Tailgate/Liftgate/Boot/Trunk Position Sensor 4 — Signal Invalid (RGTM)
1 Lincoln model · 1 documented issue
B1555 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)
B1555 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 B1555 mean on a Lincoln?
B1555 stands for "Tailgate/Liftgate/Boot/Trunk Position Sensor 4 — Signal Invalid (RGTM)." On power-liftgate vehicles the Rear Gate/Trunk Module (RGTM) sets B1555 when one of the liftgate position-sensor inputs returns an invalid/implausible signal, so the module can no longer trust its picture of where the gate is. Ford's SSM for 2020 Explorer/Aviator lists B1555 with B144D, B144E and B1556 as the code set produced by RGTM software wrongly sensing the liftgate ajar, and also documents B1555 being stored when water intrusion damages the right-hand power liftgate motor. Important scoping note: in Ford's older/legacy body-code list the same number B1555 is published as 'Ignition Run/Start Circuit Failure' for other modules — always read the code with the module that set it. On Lincoln it is documented across 1 model: Aviator.
What are the most common causes of B1555?
The most common causes of B1555 are: Outdated RGTM software (reprogram to latest level per Ford SSM), Water intrusion into the right-hand power liftgate motor/drive unit, Failed liftgate position (Hall-effect) sensor or drive unit, Damaged liftgate wiring harness or corroded connector, Latch/ajar switch fault or misaligned striker. The specific cause varies by vehicle.
How much does it cost to fix B1555 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 B1555 on a different make?
View B1555 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.