B1690 — Autolamp Delay Circuit Open #

Note: The description for this code may vary depending on the vehicle manufacturer.

• Ford: Autolamp Delay Circuit Open
• Lincoln: Autolamp Delay Circuit Open
• Mercury: Autolamp Delay Circuit Open

Summary of DTC B1690 #

The B1690 diagnostic trouble code (DTC) indicates that the autolamp delay circuit—which controls the automatic timing for turning exterior lights on and off—has an open circuit. In automotive terms, an “open circuit” means there is an unintended break or disconnection in the electrical wiring or component, preventing current from flowing as designed. This code is most commonly found in vehicles equipped with an automatic headlamp control system. The Body Control Module (BCM) or Lighting Control Module (LCM) is typically responsible for detecting this fault. Without a functioning autolamp delay circuit, the system cannot properly manage the delay that keeps your headlamps on for a set time after you exit the vehicle at night. If left unaddressed, this issue can affect both convenience and, potentially, safety.

Common Symptoms for DTC B1690 #

When the B1690 code is active, you may notice changes in how your vehicle’s exterior lights behave, especially after turning off the ignition. These symptoms are generally not critical to immediate vehicle operation, but they can be inconvenient or compromise your nighttime visibility in some situations.

• Autolamps do not stay on after shutting off the engine (no delay period)
• Autolamps fail to turn off automatically after the prescribed delay
• Manual headlamp control works, but automatic mode does not function
• Warning lights or messages related to exterior lighting on the dashboard
• Possible “chime” or alert sound upon exit
• Inconsistent or unpredictable headlamp operation at night

Probable Causes for DTC B1690 #

Several factors can trigger the B1690 code. Based on frequency and real-world repair statistics, the following causes are most common—starting with the most likely:

1. Damaged or disconnected wiring in the autolamp delay circuit (broken, corroded, or loose connectors)
2. Faulty autolamp delay relay or control module (LCM/BCM)
3. Defective headlamp switch or associated wiring
4. Blown fuse related to the exterior lighting or BCM circuit
5. Water intrusion or corrosion in fuse box or connector terminals
6. Internal failure of the BCM or LCM

Step-by-Step Diagnostic Procedure for B1690 #

To accurately diagnose a B1690 code, follow these steps in order. This ensures you address the most frequent issues first and avoid unnecessary parts replacement:

1. Confirm the code: Use an OBD-II/EOBD scanner to verify B1690 is present and not stored as a historical code.
2. Inspect fuses: Locate and check all fuses related to the autolamp, exterior lighting, and BCM/LCM circuits. Replace any blown fuses.
3. Visual inspection: Examine wiring harnesses, connectors, and grounds associated with the autolamp delay circuit for signs of damage, corrosion, or disconnection.
4. Test the headlamp switch: Using a multimeter, verify continuity and proper operation in all switch positions. Repair or replace if faulty.
5. Check relay/module: If equipped, test the autolamp delay relay or the module itself for function according to OEM wiring diagrams.
6. Scan for related codes: Look for additional BCM/LCM or lighting codes pointing to related circuit faults.
7. Consult OEM wiring diagrams: Trace the autolamp delay circuit for open or high resistance sections if the issue persists.
8. Module testing/replacement: If all else checks out, suspect an internal failure of the BCM or LCM and follow OEM test procedures before replacement.

Possible Repairs for B1690 #

The right repair depends on what the diagnostic process reveals. Here are the most common fixes, each directly related to the typical causes of this code:

• Repair or replace damaged wiring/connectors in the autolamp delay circuit
• Replace a faulty autolamp delay relay or lighting control module (as applicable)
• Replace or repair a defective headlamp switch
• Replace blown fuses and address underlying causes for fuse failure
• Clean or repair corroded fuse box or connector terminals
• Replace the BCM/LCM if confirmed faulty after all other steps

Is It Safe to Drive with Code B1690? #

In most cases, you can drive safely with code B1690 present, since it primarily affects the automatic timing of your exterior lights and not their primary function. However, you will lose the convenience of the autolamp feature, and there is a small risk of accidentally leaving your lights on or off when needed. In rare cases, if the circuit failure is accompanied by other lighting issues, nighttime visibility or vehicle signaling could be affected. If you drive frequently at night or rely heavily on automatic lighting, it’s best to address this issue promptly.

Vehicles Most Commonly Affected by B1690 #

This code is most frequently reported in Ford, Lincoln, and Mercury models equipped with automatic headlamp delay systems, especially those from the late 1990s through the mid-2010s. While other OEMs may also use similar circuits, the following vehicles are especially prone:

• Ford F-150 (2004–2014)
• Ford Expedition
• Ford Explorer (various years)
• Lincoln Navigator
• Mercury Mountaineer
• Ford Taurus
• Ford Fusion (select years with autolamp)

Common Mistakes & Best Practices with B1690 #

When troubleshooting or repairing code B1690, it’s easy to make avoidable mistakes. Here’s how to stay on track and avoid wasted time or expense:

• Replacing the BCM/LCM without thoroughly checking wiring and connectors
• Ignoring related fuses or failing to check for water intrusion/corrosion
• Overlooking the headlamp switch as a potential culprit
• Not using OEM wiring diagrams to trace the circuit
• Clearing codes before confirming the repair is successful

Best practices: Always begin with a visual inspection and fuse check, and use the official OEM service manual for wiring and component locations. Clear the code only after completing repairs and verifying proper system operation.

Quick FAQ for B1690 #

Still have questions? Here are fast answers to the most common concerns:

• Q: Will my headlights still work if B1690 is active?
  A: Yes, but only in manual mode. The automatic on/off delay feature will not function.
• Q: Can a dead battery trigger B1690?
  A: Unlikely, unless the battery failure caused a surge or loss of voltage that damaged related fuses, relays, or modules.
• Q: Is this code covered under warranty?
  A: It can be, if your vehicle is within the manufacturer’s warranty period and the failure is due to a covered component like the BCM or LCM. Check with your dealer for specifics.