B1601Body / Anti-Theft

PATS/Immobilizer - Key Not Programmed

B1601 indicates the passive anti-theft system (PATS) or immobilizer received a key signal that is not programmed or not recognized. The system may block engine starting.

🚗 Often not. If the key is not recognized, the anti-theft system may prevent starting.

MEDIUM

severity

🎯 Top Causes, Ranked by Likelihood

#1Key not programmed to the vehicle$50-$250

35%

A new or aftermarket key must be programmed to the immobilizer.

#2Faulty key transponder$50-$300

25%

A damaged transponder chip is not read correctly.

#3Weak or failed transceiver antenna$100-$400

20%

The antenna ring around the ignition may not read the key.

#4Wiring or module fault$100-$500

20%

Wiring or an immobilizer module fault prevents key recognition.

🩺 Common Symptoms

No-start or crank without start
Security or anti-theft light on
Key not recognized message
Engine stalls shortly after starting

💰 Repair Cost: DIY vs Shop

DIY Cost

$50-$300

Shop Cost

$100-$500

📋 Free OBD2 Code Cheat Sheet

The 50 most common codes with likely cause and DIY fix cost. Sent once, no spam.

🔧 How to Diagnose B1601

1Verify the key is programmed to the vehicle

2Try a known-good programmed key

3Inspect the transceiver antenna around the ignition

4Check immobilizer wiring and module communication

❓ Frequently Asked Questions

Can I drive with B1601?

Often not. If the key is not recognized, the immobilizer may prevent starting. Program or repair the key first.

What is PATS?

Passive Anti-Theft System, an immobilizer that verifies your key before allowing the engine to start.

What causes B1601?

An unprogrammed key, a faulty transponder, a weak antenna, or wiring and module faults.

🔗 Related Codes

B1602U0168U0426B2103