What Does B1601 Mean?
B1601 indicates the Passive Anti-Theft System (PATS) control module received an invalid or unrecognized transponder code from the ignition key. This security system failure prevents communication between the key's embedded chip and the vehicle's immobilizer system. The vehicle may experience a no-start condition or start then immediately stall as the anti-theft system blocks fuel delivery or ignition operation.
Safety Warning
Vehicle will likely not start or will start and immediately shut down due to anti-theft immobilizer activation. Not a safety risk while parked, but vehicle is inoperable and requires repair before driving. Towing to repair facility may be necessary.
Common Causes
35%
Damaged or unprogrammed ignition key transponder chip
30%
Faulty ignition lock cylinder with damaged transponder reader coil
20%
PATS control module communication fault or internal failure
10%
Corroded or loose wiring between ignition cylinder and PATS module
5%
Low vehicle battery voltage causing transponder read errors
Diagnostic Steps
1
Step 1: Test with a known good spare key (if available) to determine if fault is key-specific or system-wide. If spare key works normally, original key transponder is faulty.
2
Step 2: Measure battery voltage at rest and during cranking - should be above 12.4V at rest and not drop below 9.5V during cranking, as low voltage can corrupt transponder signal reading.
3
Step 3: Inspect ignition lock cylinder and transponder antenna ring for physical damage, cracks, or separation. Remove ignition switch assembly and check transponder coil wiring for breaks or corrosion at connector.
4
Step 4: Use advanced scan tool to monitor PATS module live data during key insertion and rotation, observing key code transmission and response codes to identify communication breakdown point.
5
Step 5: Check wiring continuity between ignition lock cylinder transponder antenna and PATS/BCM module using wiring diagram. Test for resistance within specification (typically 2-8 ohms for antenna coil).
6
Step 6: If all components test good, perform PATS key reprogramming procedure per manufacturer specifications. If reprogramming fails, PATS module replacement and coding required.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
B1601 indicates the Passive Anti-Theft System (PATS) control module received an invalid or unrecognized transponder code from the ignition key. This security system failure prevents communication between the key's embedded chip and the vehicle's immobilizer system. The vehicle may experience a no-st...
The most common cause of B1601 (PATS Received Incorrect Key-Code From Ignition Key Transponder) is: Damaged or unprogrammed ignition key transponder chip
Typical repair costs for B1601 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle will likely not start or will start and immediately shut down due to anti-theft immobilizer activation. Not a safety risk while parked, but vehicle is inoperable and requires repair before driving. Towing to repair facility may be necessary.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1601 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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