P0778 on Toyota: How to Diagnose & Fix
Pressure Control Solenoid B Electrical
1 Toyota model · 1 documented issue · $150-$1,500 repair
P0778 on Toyota by model: symptoms, diagnosis and fix
On higher-mileage 4Runner automatics owners report harsh/abrupt shifts, jerky 3-2 downshifts, unstable RPM blips while coasting near 40 mph, and delayed engagement. The most common mechanical cause is valve-body pressure control wear - a sticking pressure-regulator or throttle valve, or a worn shift solenoid - which raises line pressure and slams the shifts, separate from the torque-converter shudder issue. RepairPal logs hundreds of reports of these trucks not shifting correctly at high mileage. Long-neglected, dark/burnt ATF accelerates it.
Common Symptoms
- Harsh/abrupt shifts (often 3-2 downshift)
- Jerky or forced downshifts when coasting/uphill
- Delayed engagement into drive or reverse
- RPM flare/blip during deceleration
- Burnt-smelling or dark ATF
How to Fix
Start with a proper ATF service using the correct Toyota WS fluid and verify level/condition; old or wrong fluid alone causes harsh shifts. Scan for solenoid/pressure codes. If symptoms persist, the valve body (sticking regulator/throttle valve) or a worn shift solenoid is the likely fix - clean or rebuild the valve body or replace the affected solenoid; a transmission pressure test confirms a stuck regulator. Catching it early with fluid service can prevent a full rebuild.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota Genuine 00279-000T4-01 ATF Type T-IV quart
correct-fluid drain-and-fill branch for confirmed T-IV applications Fitment/availability: only transmissions whose manual/tag specifies Toyota ATF Type T-IV, including the 2003 A750E/F branch; verify build and transmission Fitment/availa…
- Toyota Genuine 00289-ATFWS World Standard ATF quart
correct-fluid drain-and-fill branch for confirmed WS applications Fitment/availability: only transmissions whose manual/tag specifies Toyota ATF WS, including later 4Runner sealed-transmission branches Fitment/availability: direct dealer…
- Genuine Toyota 35230-60010 No.2 three-way transmission solenoid
No.2 three-way-solenoid branch only when its circuit or hydraulic function is proven faulty Fitment/availability: 2003-2024 Toyota 4Runner A750-family application; confirm VIN/transmission and code/pressure diagnosis Fitment/availability…
- Genuine Toyota 35290-34010 line-pressure-control solenoid
line-pressure-control branch only after electrical and hydraulic testing Fitment/availability: 2004-2024 Toyota 4Runner catalog fitment; confirm towing/configuration note, VIN and SLT/pressure diagnosis Fitment/availability: Add to Cart …
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Sources for this issue (2)
P0778 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0778 mean on a Toyota?
P0778 stands for "Pressure Control Solenoid B Electrical." This is a transmission code. Pressure control solenoids regulate the hydraulic fluid pressure that applies the transmission's clutches for smooth, firm gear changes. P0778 specifically flags an electrical fault with Pressure Control Solenoid 'B' — the transmission control module sees that the solenoid's circuit is open, shorted, or drawing current outside the normal range. Symptoms can include harsh or slipping shifts, incorrect line pressure, or the transmission entering limp mode to protect itself. On Toyota it is documented across 1 model: 4Runner.
What are the most common causes of P0778?
The most common causes of P0778 are: Failed Pressure Control Solenoid B (electrical fault), Damaged wiring or corroded connector to the solenoid, Low, dirty, or contaminated transmission fluid, Short to power or ground in the solenoid circuit, Internal valve body wear or debris, Clogged solenoid screen or fluid passage, Faulty transmission control module (less common). The specific cause varies by vehicle.
How much does it cost to fix P0778 on a Toyota?
Published repair estimates on Toyota range from $150 to $1,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0778 on a different make?
View P0778 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.