Vehicle
Ford Falcon BA, 4.0 L six — P light flashing after a short drive.
Symptom
Limp mode with flashing P or D; throttle stuck in limp so road speed was limited to about 30 km/h.
Diagnostics
Scan codes included:
- P0753 — Shift solenoid A electrical
- P0758 — Shift solenoid B electrical
- P0763 — Shift solenoid C electrical
- P0768 — Shift solenoid D electrical
- P1748 — Electronic pressure control circuit
Wiring showed a common power feed to the transmission solenoids. EEC power relay replaced; PicoScope logged gearbox power for dropouts below 10 V — none found. PCM grounds checked OK. Conclusion: faulty PCM (part example 3R23-12A650-AH).
Second-hand PCM programmed with security access and parameter reset so the car would start. Radio then showed CODE — ACM calibration required on these Falcons after module work. On road test the speedo was wrong (~100 km/h indicated at ~60); swapping back confirmed the donor PCM was bad on speedo circuits. Tyre size / axle ratio matched (215/60R16, 3.23). Programmable parameters differed between units — using Programmable Module Installation (PMI) then parameter reset copied configuration and relinked security (parameter reset = BCM/PCM handshake; PMI copies data / VIN where applicable and can update calibration letters).
Wiring reference: Falcon BA 2003 auto harness PDF.
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