What Does B1681 Mean?
This code indicates the Passive Anti-Theft System (PATS) control module has lost communication with the transponder transceiver module that reads the chip in the ignition key. The transceiver is typically located in the ignition lock cylinder housing and reads the encrypted signal from the key to authorize engine starting. When this signal is not received, the vehicle's anti-theft system will prevent the engine from starting or running.
Safety Warning
The vehicle will likely not start or may start and immediately stall, leaving you stranded. This is not a safety hazard while driving if the engine is already running, but immediate repair is necessary to restore vehicle operability.
Common Causes
35%
Faulty or damaged PATS transceiver module ring around ignition cylinder
30%
Broken or corroded wiring harness between transceiver module and control module
20%
Failed instrument cluster or theft control module not processing transceiver signal
10%
Damaged or worn ignition key with weakened transponder chip signal
5%
Low vehicle battery voltage causing communication failure
Diagnostic Steps
1
Verify battery voltage at the battery terminals using a multimeter (should be 12.4V or higher with engine off); charge or replace battery if below 12V as low voltage can disrupt PATS communication
2
Visually inspect the wiring harness around the ignition lock cylinder for physical damage, chafing, or disconnected connectors; check connector pins for corrosion or bent terminals
3
Attempt to start the vehicle with a known-good spare key if available to rule out a faulty transponder chip in the primary key
4
Using a multimeter, test for power and ground at the PATS transceiver module connector (typically 5V or 12V reference voltage depending on manufacturer); verify continuity in signal wires between transceiver and control module
5
Remove the steering column covers and physically inspect the transceiver ring around the ignition cylinder for cracks, loose mounting, or signs of impact damage
6
If all wiring and power checks pass, replace the PATS transceiver module and perform key relearn procedure using manufacturer-specific programming tools; verify code clears and vehicle starts normally
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
This code indicates the Passive Anti-Theft System (PATS) control module has lost communication with the transponder transceiver module that reads the chip in the ignition key. The transceiver is typically located in the ignition lock cylinder housing and reads the encrypted signal from the key to au...
The most common cause of B1681 (PATS Transceiver Module Signal Is Not Received) is: Faulty or damaged PATS transceiver module ring around ignition cylinder
Typical repair costs for B1681 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle will likely not start or may start and immediately stall, leaving you stranded. This is not a safety hazard while driving if the engine is already running, but immediate repair is necessary to restore vehicle operability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1681 to identify the root cause.
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Quick Info
Category
Body
System
Anti-Theft System (PATS/Immobilizer)
Difficulty
Type
Manufacturer
Recommended Tools
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