B1689 — Autolamp Delay Circuit Failure #

Note: The description of this Diagnostic Trouble Code (DTC) may vary by manufacturer. Always check OEM documentation for vehicle-specific terminology.

• Autolamp Delay Function Circuit Failure (Ford, Lincoln, Mercury)
• Headlamp Delay Output Circuit Malfunction (Mazda)
• Headlight Auto-On Delay Circuit Error (General Motors – GM)

Summary of code B1689 #

The B1689 code indicates a problem detected within the autolamp delay circuit, which manages the time your vehicle’s automatic headlights remain on after shutting off the ignition. This system is designed to help drivers safely exit their vehicle at night by keeping the headlights illuminated for a preset period. When the Body Control Module (BCM) or a similar control unit identifies a fault in this circuit, it stores the B1689 code. While this issue typically doesn’t affect engine performance, it can impact vehicle convenience and nighttime safety.

Frequent symptoms for code B1689 #

A faulty autolamp delay circuit will usually present itself through changes in your vehicle’s lighting behavior. These issues can be subtle or obvious, depending on the nature of the fault. Watch for the following symptoms:

• Headlights turn off immediately after ignition is switched off (no delay function)
• Headlights remain on excessively long after shutdown (delay timer malfunction)
• Inconsistent autolamp delay operation
• Warning light or message on instrument cluster
• No response when adjusting autolamp delay settings
• Battery drain (if lights stay on unintentionally)

Most probable causes for code B1689 #

Several factors can trigger the B1689 code, but some are more frequent than others. The root cause is usually electrical—either within the circuit, a related component, or the BCM itself. Here’s what technicians find most often:

1. Faulty autolamp relay or timer module
2. Damaged wiring or poor connections in the autolamp circuit
3. Defective headlamp switch (including the auto-on feature)
4. Malfunctioning Body Control Module (BCM) or related control unit
5. Blown fuse in the autolamp/headlamp circuit

Step-by-step diagnostics for code B1689 #

A systematic approach is crucial to avoid overlooking a simple issue. Follow these steps to accurately identify the cause of B1689:

• Check DTCs: Scan for additional codes that might provide context or point to related systems.
• Visual inspection: Examine fuses, relays, and visible wiring for damage, corrosion, or loose connections.
• Test headlamp switch: Verify that all switch positions function properly, including the auto setting.
• Check autolamp relay/timer operation: Listen for relay clicks or use a multimeter to confirm activation and signal flow.
• Inspect BCM connections: Ensure connectors are secure and free from moisture or corrosion.
• Perform circuit tests: Use a wiring diagram to check for voltage and continuity along the autolamp delay circuit.
• Consult OEM service information: Some vehicles require advanced diagnostics or BCM reprogramming—always refer to manufacturer data.

Possible repairs for code B1689 #

Once you’ve pinpointed the source, the following repairs are commonly recommended for B1689:

• Replace a faulty autolamp relay or timer module
• Repair or replace damaged wiring/connectors in the autolamp circuit
• Replace a defective headlamp switch
• Replace or reprogram the BCM (if internal failure is confirmed)
• Replace blown fuses and correct the root cause of the short circuit

Is it safe to drive with code B1689? #

Limited: You can generally continue driving with code B1689 present, as it does not affect the engine or core safety systems. However, if the autolamp delay is not functioning, your headlights may turn off too soon or stay on too long, potentially compromising visibility when exiting the vehicle at night—or draining your battery if the lights don’t turn off. For peace of mind and to avoid inconvenience, address the issue as soon as practical.

Vehicles most commonly affected by code B1689 #

B1689 is most frequently reported on vehicles equipped with factory autolamp or automatic headlight delay systems, especially from these manufacturers:

• Ford (Fusion, Escape, F-150, Taurus, Explorer, Edge, Mustang)
• Lincoln (MKZ, MKX, Navigator, Town Car)
• Mazda (6, CX-5, Tribute)
• Mercury (Milan, Mountaineer, Sable)
• General Motors (GM) vehicles with auto headlamp features

Common mistakes & best practices for code B1689 #

Misdiagnosis is a risk with electrical codes like B1689. Avoid these common errors and follow best practices:

• Replacing the BCM prematurely without confirming circuit integrity
• Overlooking blown fuses or relays as a simple fix
• Neglecting to check headlamp switch operation, especially the auto mode
• Not consulting OEM wiring diagrams for accurate circuit tracing
• Skipping a thorough visual inspection for corrosion or connector issues

Quick FAQ for code B1689 #

Here are concise answers to some common questions about B1689:

• Q: Will this code drain my battery?
  A: It can, if the headlights remain on unintentionally. Monitor your vehicle to ensure lights turn off properly after shut-down.
• Q: Can I reset the code and ignore it?
  A: Resetting may clear the code temporarily, but if the underlying issue remains, the code and symptoms will return. Proper diagnosis and repair are recommended.