OBD Code B1689: Autolamp Delay Circuit Failure

Q: What does OBD code B1689 mean?

Autolamp Delay Circuit Failure. The automatic headlight delay circuit isn't working properly, similar to a timer that won't start or stop when it should. Your headlights may not turn off after you exit the vehicle or delay activation when needed.

Q: How do I fix OBD fault code B1689?

Locate the relay in the dashboard fuse/relay box and swap with an identical relay to test for failure.. Inspect all connections to the light control module for corrosion, loose pins, or damaged insulation and repair as needed.. Replace the integrated light control module if relay and wiring are confirmed functional.

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What This Actually Means

In plain language — no jargon

The automatic headlight delay circuit isn't working properly, similar to a timer that won't start or stop when it should. Your headlights may not turn off after you exit the vehicle or delay activation when needed.

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Symptoms You May Notice

3 known symptoms for this code

Headlights stay on continuously or won't turn off after ignition is off

Headlights fail to activate with automatic delay when entering dark conditions

Inconsistent or missing headlight fade-out behavior

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Embedded Systems Insight

What the ECU/ECM is actually computing

The ECU monitors the autolamp delay module's response time and signal integrity when the ignition transitions from run to off. It measures voltage and timing delays expected from the light delay relay to confirm proper circuit operation. A missing or delayed signal indicates wiring faults, relay failure, or control module malfunction.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Delay Signal Response Time	0.5-2.5 seconds	No signal or >3 seconds
Relay Output Voltage	12-14V during delay cycle	<5V or open circuit

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Autolamp delay relay

Locate the relay in the dashboard fuse/relay box and swap with an identical relay to test for failure.

2

Wiring harness and connectors

Inspect all connections to the light control module for corrosion, loose pins, or damaged insulation and repair as needed.

3

Headlight control module

Replace the integrated light control module if relay and wiring are confirmed functional.