B1693
Autolamp On Circuit Failure
Body Chassis/Safety Autolamp Circuit 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

The instrument cluster's automatic headlight system isn't working properly—the ECU can't turn on the autolamp circuit when it should. Think of it like a light switch that's stuck and won't respond to the sensor telling it to flip on.

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Symptoms You May Notice
3 known symptoms for this code
Headlights don't automatically activate in low-light conditions
Instrument cluster warning light stays on or flickers
Autolamp feature is disabled or non-functional
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the autolamp control circuit for proper voltage and current flow when the automatic headlight sensor detects darkness. It checks for circuit continuity and detects open circuits, shorts, or excessive resistance in the relay or wiring. If voltage doesn't reach expected levels within the specified timeframe, a fault is logged.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Autolamp Circuit Voltage 12V (battery voltage when activated) Below 10V or open circuit detected
Circuit Resistance Less than 5 ohms Greater than 10 ohms or infinite resistance
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Autolamp relay
Locate the relay in the fuse box (check owner's manual), remove it, and replace with an OEM or quality aftermarket relay.
2
Wiring harness connector
Inspect the autolamp circuit connector at the headlight module for corrosion, loose pins, or damage; clean contacts with electrical contact cleaner or reseat the connector.
3
Autolamp control module or headlight switch
Test continuity through the autolamp switch with a multimeter; if open, replace the headlight switch assembly or dedicated autolamp module.