OBD-II Code
P0784
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$400–$8,000
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$400 (fluid + filter + solenoid) to $8,000 (AS69RC rebuild).
P0784 is the 4-5 shift malfunction — TCM commanded a 4-5 upshift, didn't see the input/output ratio drop to the fifth-gear target (around 0.85:1 on a typical 6-speed's fifth, around 0.7:1 on a 5-speed's fifth), and set the code.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0784 is the 4-5 shift malfunction — TCM commanded a 4-5 upshift, didn't see the input/output ratio drop to the fifth-gear target (around 0.85:1 on a…
P0784 is the 4-5 shift malfunction — TCM commanded a 4-5 upshift, didn't see the input/output ratio drop to the fifth-gear target (around 0.85:1 on a typical 6-speed's fifth, around 0.7:1 on a 5-speed's fifth), and set the code. This code only applies to transmissions with five or more forward gears, so you're looking at a modern 5/6/8/10-speed automatic, not an old 4-speed.
Cheapest-first ladder
- Fluid level + condition. On these modern units, the fluid spec is platform-specific (Mercon LV for Ford 6R80, Dexron HP/ULV for newer GM, ZF Lifeguard 8 for ZF 8HP, Toyota WS for Aisin) and using the wrong fluid is itself a P078X cause.
- Live data during a 4-5 shift event (highway cruise, light throttle around 55-70 mph); watch for shift flare or harsh apply.
- Read all codes — P0784 paired with PCS solenoid codes (P0745, P0775) points at the valve body; paired with P0729 (gear ratio incorrect, fifth) confirms the fifth-element clutch is slipping.
- Drop the pan, magnet inspect, fluid sample sent to a lab if the customer is high-mileage and considering a rebuild. The expensive-misdiagnosis caveat — and this one's load-bearing: don't condemn the trans before confirming fluid level + condition. A burned-fluid 4L60E with a P0784 needs internal repair, not a $90 solenoid; the same logic applies to every modern multi-speed automatic, where the cost of a rebuild is 3-5x what it was for the 4-speed predecessors.
Vehicle-specific patterns2010-2019 Ford 6R80 (F-150, Mustang, Explorer) throws P0784 from valve-body wear and lead-frame degradation; Ford sells the lead frame as a service p…
- 2010-2019Ford 6R80 (F-150, Mustang, Explorer) throws P0784 from valve-body wear and lead-frame degradation; Ford sells the lead frame as a service part, $200-400, but proper diagnosis often points at the full valve-body rebuild at $1,400-2,800. 2007-present GM 6L80/6L90 (Silverado, Tahoe, Camaro SS) throws P0784 from valve-body wear and from 3-5-R clutch failure (this is the clutch pack that applies in 3rd, 5th, and Reverse on the 6L80, so a worn 3-5-R clutch presents as P0784 AND reverse slip simultaneously); rebuild is $2,400-4,000. 2009-present ZF 8HP (RAM 1500, BMW, JLR) throws P0784 from mechatronic problems and clutch wear; ZF mechatronic service or rebuild is $2,800-5,500. 2013-present Aisin AS69RC (RAM 2500/3500 HD) throws P0784 from internal failure and is a $5,500-8,000 rebuild given the part costs and labor.
Estimated repair$400 (fluid + filter + solenoid) to $8,000 (AS69RC rebuild).
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