What Does B1605 Mean?
This code indicates the Body Control Module (BCM) has detected a short to battery voltage in the anti-theft indicator lamp circuit. This means the circuit is receiving constant battery voltage when it should not be, causing the anti-theft/security light to illuminate improperly or remain on continuously. The BCM monitors this circuit to control the security system status indicator and has detected an abnormal voltage condition suggesting a wiring fault or component failure.
Common Causes
45%
Damaged or chafed wiring harness causing short to power in the anti-theft lamp circuit
30%
Faulty anti-theft indicator lamp assembly with internal short to power
15%
Corroded or damaged connector at BCM or lamp assembly causing cross-circuit short
10%
Failed Body Control Module with internal driver circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of the anti-theft indicator lamp and instrument cluster for signs of water intrusion, burnt components, or damaged wiring. Check all connectors along the lamp circuit for corrosion, pushed-out pins, or melted terminals.
2
Step 2: Disconnect the anti-theft indicator lamp connector and use a digital multimeter to measure voltage at the lamp side connector with ignition on. Should read 0V; if battery voltage is present, trace wiring from lamp to BCM for short to power.
3
Step 3: With lamp disconnected, measure resistance from the BCM control wire to battery positive and to ground. Should read open circuit (OL) to battery positive; any continuity indicates a short. Check wiring routing near sharp edges, moving components, or heat sources.
4
Step 4: If wiring tests normal, substitute a known-good anti-theft indicator lamp or bulb assembly. Clear codes and test. If code returns, suspect BCM internal fault and perform BCM voltage supply and ground integrity tests per manufacturer specifications.
5
Step 5: Reconnect all components, clear diagnostic codes, and perform operational test of anti-theft system through multiple lock/unlock cycles. Monitor live data for lamp circuit voltage while cycling system to confirm repair.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a short to battery voltage in the anti-theft indicator lamp circuit. This means the circuit is receiving constant battery voltage when it should not be, causing the anti-theft/security light to illuminate improperly or remain on continuo...
The most common cause of B1605 (Lamp Anti-Theft Indicator Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to power in the anti-theft lamp circuit
Typical repair costs for B1605 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle drivability or safety and the vehicle is safe to operate normally. The primary concern is proper security system indication functionality and potential battery drain if the lamp remains constantly illuminated.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1605 to identify the root cause.
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Quick Info
Category
Body
System
Anti-Theft/Security System
Difficulty
Type
Manufacturer
Recommended Tools
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