What Does B1694 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the automatic headlamp system's control circuit. The autolamp feature, which automatically turns headlights on/off based on ambient light conditions, is not receiving proper electrical continuity. The BCM monitors this circuit and sets this code when it detects voltage or resistance values inconsistent with normal closed-circuit operation.
Common Causes
40%
Damaged or corroded wiring harness between BCM and autolamp sensor or headlight switch
30%
Faulty ambient light sensor (photocell) with internal open circuit
20%
Defective headlight switch with failed autolamp circuit contacts
10%
Failed BCM with internal driver circuit failure
Diagnostic Steps
1
Step 1: Perform visual inspection of the ambient light sensor (typically located on dashboard near windshield) and its wiring connector for physical damage, corrosion, or disconnection. Check connector pins for spread or corrosion and ensure connector is fully seated.
2
Step 2: Using a digital multimeter, check for continuity between the BCM connector and the autolamp sensor connector with ignition off. Verify circuit resistance is below 5 ohms. Also check for short to ground (should read OL/infinite resistance).
3
Step 3: With ignition on, backprobe the ambient light sensor connector and verify reference voltage (typically 5V or 12V depending on manufacturer) is present from BCM. If no voltage present, trace circuit back toward BCM for open.
4
Step 4: Test the ambient light sensor operation by measuring resistance or voltage signal while covering/uncovering sensor with hand. Values should change smoothly. If sensor tests good but circuit is open, inspect headlight switch connections and BCM harness connector.
5
Step 5: After repair, clear codes, cycle ignition, and test autolamp function by covering sensor in daylight or starting vehicle in dark conditions. Verify headlights activate automatically and code does not return.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the automatic headlamp system's control circuit. The autolamp feature, which automatically turns headlights on/off based on ambient light conditions, is not receiving proper electrical continuity. The BCM monitors this...
The most common cause of B1694 (Autolamp On Circuit Open) is: Damaged or corroded wiring harness between BCM and autolamp sensor or headlight switch
Typical repair costs for B1694 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive, but automatic headlight functionality is disabled requiring manual headlight operation. Repair at convenience to restore automatic lighting convenience and ensure headlights are turned on during low-light conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1694 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Lighting System
Difficulty
Type
Manufacturer
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