B1533 on 2018-2022 Ford Expedition: Headlamp Switch Failure Causes and Fixes

What's Unique About the 2018-2022 Ford EXPEDITION

This issue is so specific to this platform (and other contemporary Fords) that Ford issued a Technical Service Bulletin (TSB SSM 51617) to address it. The problem isn't a simple electrical short but a flaw in the switch's internal logic communicating over a LIN bus to the BCM. This means that simply replacing the switch with an old stock part might not work; an updated part from the manufacturer is required to permanently fix the issue. The TSB confirms the cause and directs technicians to replace the switch.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Headlights turn on by themselves while the vehicle is parked and off.
• Headlights operate intermittently when the vehicle is off.
• Dead battery due to parasitic draw from the headlamps activating.
• Warning chime (dinger) sounds when opening the door, indicating lights are on even though the switch is in 'Auto' or 'Off'.

Most Likely Causes

1. Faulty Headlamp Switch 🔴 High Probability → Shop Combination Switch Ford has identified a flaw in the internal logic of the original-equipment headlamp switch for this specific model range, as documented in TSB SSM 51617. This issue is widespread across various Ford and Lincoln models from the same era.
   How to confirm: Confirm that the B1533 code is present in the Body Control Module (BCM) and observe if the headlights turn on while the vehicle is off. Owners report witnessing the headlights and taillights on after the vehicle has been locked and sitting for some time. 🎬 Watch: See an example of headlights staying on while parked. Given the known issue documented in the TSB, if both the code and symptom are present, the switch is the definitive cause.
   Typical fix: Replace the headlamp switch with the new, updated OEM part. The service base part number is 11654, and the specific part number is DG9Z-11654-BA. The replacement is a simple, tool-free process that involves prying the switch assembly out of the dashboard, disconnecting the electrical connector, and plugging in the new switch. 🎬 See this walkthrough for a similar Ford headlight switch replacement.
   Est. part cost: $60-$91

Diagnosis Steps

1. Use an OBD-II scanner to confirm that code B1533 is stored in the Body Control Module (BCM). Often, this will appear with a Failure Type Code (FTC) of '08' (B1533:08), indicating a bus signal/message failure.
2. Observe the vehicle after it has been turned off and locked. Check to see if the headlights turn on by themselves. This may be intermittent and not happen every time.
3. Reference Ford TSB SSM 51617, which directly links these symptoms and this DTC to a faulty headlamp switch.
4. Given the known issue, the most direct diagnostic step is to assume the headlamp switch is faulty and proceed with replacement using OEM part DG9Z-11654-BA.
5. No complex wiring or module diagnostics are typically needed, as the TSB identifies the switch as the definitive cause. The switch communicates with the BCM over a LIN bus, so a simple voltage or resistance test on the pins is not sufficient for diagnosis.

Parts You'll Likely Need

• Headlight Switch (OEM #DG9Z-11654-BA) — This is the component identified by Ford's TSB as having faulty internal logic, causing the parasitic drain and setting code B1533. It is the updated part designed to correct the condition.
  Trusted brands: Motorcraft
  OEM price range: $60-$91
  Aftermarket price range: $57-$81

Technical Service Bulletins (TSBs) & Recalls

• SSM 51617: States that 2018-2022 Expedition vehicles with DTC B1533 and intermittent headlamp operation when OFF may have a faulty headlamp switch. It recommends replacing the switch (service base part number 11654) to correct the condition.
• SSM 51321: An earlier version of the TSB for the same issue on 2018-2022 Expeditions, which noted that a new headlamp switch was under development and to schedule customer appointments for a later date.

Platform-Specific Known Issues

• A known issue documented in TSB SSM 51617 describes how the internal logic of the headlamp switch can fail, causing the headlights to turn on when the vehicle is off and setting code B1533. Ford developed a new part to correct this condition.
• A forum thread on the Ford Expedition Forum titled 'Headlights turn on by themselves?!' from May 2023 details a user's 2022 Expedition exhibiting the exact symptoms, with others confirming similar experiences.

Hidden / Shadow Codes Worth Checking

• B1533:08: This is the full code often stored in the BCM. The ':08' is a Failure Type Code (FTC) that specifies a 'Bus Signal/Message Failure'. This confirms the issue is not a simple short or open circuit, but a communication problem between the headlamp switch module and the BCM over the LIN bus. (see via A professional-grade scan tool like Ford's IDS or a high-end consumer scanner that can read manufacturer-specific DTCs and their FTCs from the BCM.)

Scan Tool Commands That Help

• Ford IDS (Integrated Diagnostic System): BCM On-Demand Self-Test — This test can be run before and after the repair. Before replacement, it will confirm the B1533:08 code is present. After replacing the switch, running the self-test again and clearing all DTCs will verify that the new switch is communicating correctly and the fault is resolved.
• Ford IDS / FORScan: BCM Module Reset / Clear DTCs — After the physical replacement of the headlamp switch, it is critical to clear the stored B1533 code from the BCM. In some rare cases, if symptoms were to persist, a full BCM module reset (a function available in advanced scan tools) could be performed to re-initialize all body modules, though this is not typically required for this specific repair.

Real Owner Repair Stories

• MachEforum user 'breeves002' (2021 Ford Mustang Mach-E) — Door chime would sound as if the lights were left on, even though the switch was in 'Auto'. The switch's own backlight would be off. Turning the knob would resolve it temporarily. Stored codes B1533:08 (Headlamp Switch Module) and B162E:01 (Max Defrost LED).
  ❌ Tried (didn't work) The user noted it started after dealer software updates, but correctly identified this as correlation, not causation.
  ✅ What actually fixed it The user diagnosed it as a faulty headlamp switch based on the LIN bus communication codes. The ultimate fix, per the later-released TSB, is the replacement of the switch with the updated part.

OEM Part Supersession History

• FL3Z-11654-BA (and others) → DG9Z-11654-BA — The original part numbers contained faulty internal logic that caused the intermittent communication failure and parasitic draw. The DG9Z-11654-BA part is the corrected version.
  Heads up: While older part numbers like FL3Z-11654-BA may physically fit, they contain the original defect and will not solve the B1533 issue. It is critical to use the updated DG9Z-11654-BA part.

Model Year Variations Within This Range

• 2018-2021 vs 2022: The physical procedure for removing the headlamp switch varies slightly. While both are pried from the dash, the surrounding trim and attachment points differ between the pre-facelift (2018-2021) and facelift (2022) Expedition models. Ford provides separate workshop manual procedures for each.