P1734: Gear Control Malfunction

P1734 is a transmission fault that tells you the transmission control system has detected a malfunction in gear control. The transmission control module continuously monitors gear selection, shift solenoid operation, and gear ratio confirmation. When something in that process falls outside expected parameters, whether the transmission cannot achieve the commanded gear or the control circuit for gear selection is behaving incorrectly, P1734 is logged.

Causes can include a faulty shift solenoid or solenoid circuit, low or degraded transmission fluid affecting hydraulic pressure, an internal transmission mechanical fault, or a wiring problem in the gear control circuit. Start by checking the transmission fluid level and condition. Burnt, dark, or low fluid is a common contributor to transmission faults and is the cheapest thing to rule out first. From there, a scan tool that can read live transmission data will help identify whether the issue is electrical or hydraulic.

P1734 is rated high severity. A gear control malfunction can result in harsh shifting, slipping gears, the transmission getting stuck in a single gear, or the vehicle entering limp mode to protect the drivetrain. Do not continue driving normally with this fault active. Get the vehicle scanned properly and address the root cause as soon as possible to avoid turning a manageable repair into a transmission rebuild.