What Does B1691 Mean?
B1691 indicates the Body Control Module (BCM) has detected a short to battery voltage in the autolamp delay circuit. This circuit controls the automatic headlight delay feature that keeps exterior lights illuminated for a preset time after the vehicle is turned off. The BCM has detected unwanted battery voltage present on the control circuit when it should be at ground or open circuit, indicating a wiring fault or component failure.
Common Causes
45%
Damaged or chafed wiring harness causing short to B+ voltage in autolamp delay circuit
25%
Failed Body Control Module with internal short in autolamp delay driver circuit
20%
Faulty headlight switch assembly with internal short to power
10%
Damaged autolamp sensor or photocell with internal short circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of all wiring in the autolamp delay circuit, especially at door jambs, A-pillars, and dash area. Look for chafed, pinched, or damaged insulation that could contact battery voltage sources.
2
Step 2: Disconnect the headlight switch connector and measure voltage on the autolamp delay circuit wire at the BCM harness connector. Use a digital multimeter set to DC voltage; reading should be 0V with switch disconnected. If battery voltage is present, wiring harness has a short to B+.
3
Step 3: If no voltage found in Step 2, disconnect the autolamp sensor/photocell connector and retest the circuit. If voltage drops to 0V, the sensor has an internal short and requires replacement.
4
Step 4: If voltage remains present with all components disconnected, isolate the short by checking continuity between the autolamp delay circuit wire and known B+ sources along the harness routing. Repair or replace damaged harness sections.
5
Step 5: If no external shorts are found, perform BCM self-test using enhanced diagnostics to verify internal driver circuit operation. Monitor autolamp delay output state while commanding on/off through bidirectional controls.
6
Step 6: Clear codes, reconnect all components, and test autolamp delay function through complete cycle. Verify code does not return and headlights properly delay off after ignition shutdown.
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
B1691 indicates the Body Control Module (BCM) has detected a short to battery voltage in the autolamp delay circuit. This circuit controls the automatic headlight delay feature that keeps exterior lights illuminated for a preset time after the vehicle is turned off. The BCM has detected unwanted bat...
The most common cause of B1691 (Autolamp Delay Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to B+ voltage in autolamp delay circuit
Typical repair costs for B1691 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects the automatic headlight delay convenience feature. Headlights will still function normally for driving; however, the delay-off feature may not work properly, potentially draining the battery if lights remain on unintentionally.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1691 to identify the root cause.
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Quick Info
Category
Body
System
Exterior Lighting System
Difficulty
Type
Manufacturer
Recommended Tools
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