What Does B1602 Mean?
This code indicates the Passive Anti-Theft System (PATS) or immobilizer system detected corrupted or improperly formatted data transmitted from the ignition key transponder chip. The vehicle's security module is unable to authenticate the key because the transponder signal does not match the expected protocol or format. This is a communication error between the transponder in the key and the theft deterrent receiver in the ignition system.
Safety Warning
Vehicle will likely not start or may start intermittently then stall, leaving you stranded. No direct safety risk while driving if vehicle does run, but immediate repair is necessary to restore reliable starting capability.
Common Causes
35%
Damaged, worn, or weak transponder chip in the ignition key causing signal degradation or corruption
30%
Faulty or contaminated transponder receiver antenna ring around the ignition cylinder
20%
Electrical interference or damaged wiring between transponder antenna and security module
10%
Corrupted security module programming or module internal failure
5%
Use of incorrect, unprogrammed, or aftermarket key not compatible with vehicle security system
Diagnostic Steps
1
Step 1: Verify the ignition key being used is the original factory key or properly programmed spare - attempt to start vehicle with all available keys to determine if issue is key-specific or system-wide
2
Step 2: Inspect the ignition key for physical damage, cracks, or separation of transponder chip housing; check for metallic objects or aftermarket key covers that could shield the transponder signal
3
Step 3: Remove ignition lock cylinder trim and visually inspect transponder antenna ring for damage, corrosion, proper seating around cylinder, and secure electrical connections
4
Step 4: Using a multimeter, test continuity and resistance of wiring between transponder antenna connector and security module; check for shorts to ground or power (typical resistance 2-10 ohms depending on manufacturer)
5
Step 5: Monitor live data stream for transponder signal strength or key code reception status while cycling key on/off to identify intermittent communication failures
6
Step 6: If all physical components test correctly, attempt to re-program the key to the security module using manufacturer-specific procedure or have dealer perform key re-initialization and verify module software is current version
Estimated Repair Cost
$85 - $650
Parts + labor, varies by vehicle and location
This code indicates the Passive Anti-Theft System (PATS) or immobilizer system detected corrupted or improperly formatted data transmitted from the ignition key transponder chip. The vehicle's security module is unable to authenticate the key because the transponder signal does not match the expecte...
The most common cause of B1602 (PATS Received Invalid Format Of Key-Code From Ignition Key Transponder) is: Damaged, worn, or weak transponder chip in the ignition key causing signal degradation or corruption
Typical repair costs for B1602 range from $85 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle will likely not start or may start intermittently then stall, leaving you stranded. No direct safety risk while driving if vehicle does run, but immediate repair is necessary to restore reliable starting capability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1602 to identify the root cause.
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Quick Info
Category
Body
System
Anti-Theft/Security System
Difficulty
Type
Manufacturer
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