P1259high severityPowertrain
Immobilizer to PCM Signal Error
on 2021 Ford Mustang Mach-E Standard Range Dual Motor AWD · RWD
What this code means
The PATS (Passive Anti-Theft System) immobilizer is not communicating properly with the PCM. The security signal between the instrument cluster and PCM does not match, preventing proper engine operation.
Symptoms
- Check Engine Light
- Engine may not start
- Security light flashing
- Engine starts then dies
Common causes
- Faulty transponder key
- PATS transceiver malfunction
- Instrument cluster communication error
- PCM not properly programmed
- Low battery voltage during key programming
Diagnostic steps
- Try a different programmed key
- Check PATS indicator light behavior
- Verify key is programmed (check NUMKEYS PID)
- Inspect PATS transceiver around ignition cylinder
- Check battery voltage
Repair notes
Try second key. Reprogram keys if needed. Replace PATS transceiver if faulty. May require dealer-level scan tool.
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P0125
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