B1681
PATS Transceiver Module Signal Is Not Received
Body Chassis/Safety Anti-Theft System 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

Your car's security system isn't communicating with the engine computer. It's like a security guard who stopped checking in—the main office doesn't know if everything is okay.

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Symptoms You May Notice
3 known symptoms for this code
Engine won't start or cranks but fails to start
Vehicle security light stays on or flashes continuously
Reduced engine power or limp mode activation
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors radio frequency signals from the PATS (Passive Anti-Theft System) transceiver module to confirm a valid key is present. The transceiver should continuously broadcast a valid security code during key-on and engine operation. If the ECU fails to detect this signal within expected timeframes, the fault is triggered.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
PATS Signal Detection Valid RF signal received continuously during cranking No valid signal detected or signal loss >500ms
Module Communication Status Module responds to ECU queries with valid handshake No response or corrupted data from transceiver module
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Car key battery
Replace the battery inside your key fob; a weak battery prevents signal transmission.
2
PATS transceiver antenna connector
Inspect and reseat the antenna connector under the steering column for corrosion or loose pins.
3
PATS transceiver module
Replace the module located near the steering column if signal detection remains absent after other checks.