PATS Ring Antenna Signal Lost
The B1681 code indicates that the Powertrain Control Module (PCM) or the Passive Anti-Theft System (PATS) module is not receiving any signal from the ring antenna (transceiver) located around the ignition key cylinder. This antenna generates an electromagnetic field to power and read the key's transponder, then sends the data via serial communication to the control module. A total loss of signal suggests an open circuit, a faulty transceiver module, or a problem in the receiving module that prevents reading the key code, activating the anti-theft mode and preventing the engine from starting.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or internally damaged PATS ring antenna (transceiver)
- Open circuit, short to ground, or short to power in the wiring between the transceiver and the PCM/PATS module
- Corroded, bent, or disconnected pins in the transceiver harness connectors
- Unprogrammed or damaged key transponder (no response detected by the transceiver)
- Internal failure of the PCM or PATS control module preventing signal processing
- Severe electromagnetic interference blocking communication between the key and transceiver
3. Symptoms You Will Notice
- Engine cranks but does not start
- Security indicator light flashing or staying on
4. Step-by-Step Diagnosis
Check for any aftermarket accessories or modifications that may cause interference
Inspect the ring antenna connector and wiring for damage, corrosion, or loose connections
Test the ring antenna resistance and compare to manufacturer specifications
Verify power and ground at the transceiver connector
Attempt to start with a known good programmed key to rule out key transponder failure
If all else fails, test the PCM/PATS module for proper communication and signal processing
5. Frequently Asked Questions
Is it safe to drive?▼
No, the vehicle will likely not start or may stall while driving due to the anti-theft system being activated. It is not safe to drive.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the ring antenna, key, or control module needs replacement and labor rates.