B1603: Anti-Theft Indicator Circuit Malfunction
The B1603 code indicates a fault in the anti-theft system indicator lamp circuit, part of the Passive Anti-Theft System (PATS). The PATS control module has detected an electrical anomaly—such as a missing signal, short circuit, or open circuit—in the circuit that powers or controls the dashboard LED or lamp that informs the driver of the security system status. This prevents proper communication between the module and the indicator.
1. Commonly Affected Makes
2. Most Common Causes
- Burnt-out anti-theft indicator bulb or LED
- Indicator circuit wiring shorted to ground or voltage
- Open circuit in the indicator wiring (broken or disconnected)
- Corroded, bent, or loose pins in the PATS module or instrument cluster connector
- Failed or damaged PATS control module
3. Symptoms You Will Notice
- Anti-theft indicator light on the dashboard stays off or behaves erratically
- Engine may crank but not start (if PATS fails to disarm)
- Security system may not arm or disarm properly
4. Step-by-Step Diagnosis
Check the anti-theft indicator bulb/LED for continuity and replace if burnt out.
Inspect the wiring and connector for the indicator circuit for shorts, opens, or corrosion.
Test the PATS module output to the indicator circuit with a multimeter.
If wiring and bulb are good, suspect a faulty PATS module and perform module self-test or replacement.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is generally safe to drive, but the anti-theft system may not function correctly, and in some cases the engine may not start if the PATS fails to disarm.
How much does it cost to fix?▼
Repair costs typically range from $50 to $200 for bulb or wiring fixes, and $200 to $600+ if the PATS module needs replacement.