P0784: 4-5 Shift

What does P0784 mean?

Shift codes are a functional check of the gear change itself: the module compares the commanded shift with the speed trace and flags a shift that takes too long, is too short or abrupt, does not happen, flares or ties up. Ford does not use P0780–P0784 (its shift completion check feeds the solenoid codes), nor do GM's 2018–2025 tables. P0784 names the 4–5 shift as the faulty one, up or down; slip in a steady gear is reported by the ratio codes instead. It only exists on transmissions with five or more gears. No manufacturer document available to us uses this code; GM's 2006 five-speed tables run the shift time check under P0780. High engine speed on the motorway from a missing fifth gear is typical.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Harsh, delayed or missing 4-5 shift
• Engine flare during the shift
• Warning lamp
• Limp mode

Common causes

• High Fluid level wrong, fluid worn or contaminated
• High Valve body, shift or pressure valve sticking
• Medium Worn clutches or bands
• Medium Module software or shift adaption
• Low Faulty speed sensor signal

Likelihood is a general estimate across vehicles; your make and model may differ.