What does code P1778 mean?

Q: What does code P1778 mean?

Transmission Reverse IP Circuit. P1778 on a Jaguar means the transmission control module (TCM) has detected an electrical fault in the reverse IP circuit, which is the internal wiring path that carries current to the reverse engagement solenoid inside the gearbox. The TCM monitors the circuit for expected voltage and current when reverse is commanded, and it sets this code when the signal falls outside the programmed window, indicating an open, short, or high-resistance connection rather than a mechanical reverse gear failure.

DTC codes / Jaguar codes / P1778

P1778 · JaguarTransmission Reverse IP Circuit

P1778 on a Jaguar means the transmission control module (TCM) has detected an electrical fault in the reverse IP circuit, which is the internal wiring path that carries current to the reverse engagement solenoid inside the gearbox. The TCM monitors the circuit for expected voltage and current when reverse is commanded, and it sets this code when the signal falls outside the programmed window, indicating an open, short, or high-resistance connection rather than a mechanical reverse gear failure.

SystemPowertrain

Code typeJaguar specific

SeverityMedium

Fix difficultyProfessional

AreaTransmission

Guidance is general and written for Jaguar vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.