What this code means

The PATS (Passive Anti-Theft System) has detected a potential theft condition and has immobilized the engine. The PCM will not enable fuel injection or ignition until proper authentication is received from a programmed key. Common on Ford F-150, Mustang, Explorer, Fusion, and E-Series.

Symptoms

• Engine cranks but will not start
• Engine starts then immediately shuts off
• Security/theft light flashing on dashboard
• Check Engine Light

Common causes

• Key not programmed to vehicle
• Faulty transponder chip in key
• Malfunctioning PATS transceiver module
• Corrupted PCM or instrument cluster security codes
• Low battery voltage during start
• Recent battery replacement or jump-start
• Aftermarket remote start system interference
• New PCM or instrument cluster installed without programming

Diagnostic steps

1. Try a second programmed key — if it works, first key is faulty
2. Check NUMKEYS PID in PATS data (needs at least 2 keys programmed)
3. Observe PATS indicator light (on for 3 sec = normal; flashing = fault)
4. Check battery voltage (low voltage can cause false trigger)
5. Inspect steering column PATS transceiver for damage
6. Check for aftermarket remote start system interference

Repair notes

Try second key first. Reprogram keys using two-key procedure. If transceiver or PCM is faulty, both PCM and instrument cluster may need replacement and reprogramming together. Dealer-grade scan tool typically required.

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