What Does B1604 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the anti-theft indicator lamp circuit. The anti-theft indicator is typically a dash-mounted LED that flashes when the vehicle's security system is armed. An open circuit means there is a break in the electrical path between the BCM and the indicator lamp, preventing the BCM from controlling or monitoring the lamp's operation.
Common Causes
35%
Failed anti-theft indicator lamp or LED bulb burnout
30%
Broken or damaged wiring between BCM and indicator lamp
20%
Loose or corroded connector at instrument cluster or BCM
10%
Failed Body Control Module output driver circuit
5%
Blown fuse in instrument panel circuit
Diagnostic Steps
1
Step 1: Visually inspect the anti-theft indicator lamp in the instrument cluster for physical damage or obvious bulb failure. Note if lamp was previously functional.
2
Step 2: Locate and inspect all fuses related to the instrument cluster and body control circuits. Test suspect fuses with a multimeter for continuity.
3
Step 3: Access the instrument cluster connector and BCM connector. Inspect for corrosion, loose pins, or damaged terminals. Check for proper seating of all connectors.
4
Step 4: Using a wiring diagram, identify the anti-theft indicator lamp control wire. With ignition off, disconnect the instrument cluster and measure resistance from the BCM connector pin to the cluster connector pin. Reading should be less than 5 ohms; infinite resistance confirms open circuit.
5
Step 5: If wiring tests good, use a multimeter to check for voltage output from the BCM at the appropriate pin during system arming cycle. No voltage with good ground indicates BCM driver failure.
6
Step 6: After repair, clear codes and cycle the ignition. Arm the security system and verify the anti-theft indicator flashes properly and no codes 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 anti-theft indicator lamp circuit. The anti-theft indicator is typically a dash-mounted LED that flashes when the vehicle's security system is armed. An open circuit means there is a break in the electrical path be...
The most common cause of B1604 (Lamp Anti-Theft Indicator Circuit Open) is: Failed anti-theft indicator lamp or LED bulb burnout
Typical repair costs for B1604 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This fault does not affect vehicle safety or drivability and the vehicle can be operated normally. The only impact is loss of visual confirmation that the anti-theft system is armed, which may result in reduced theft deterrence or unknown security system status.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1604 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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