P0778 on Jaguar: How to Diagnose & Fix
Pressure Control Solenoid B Electrical
1 Jaguar model · 1 documented issue · 1 critical · $900-$3,000 repair
P0778 on Jaguar by model: symptoms, diagnosis and fix
The ZF 6HP26 (2006-2009 4.2L cars) and ZF 6HP28 (2009-2014 5.0L cars) automatic used in the X150 XK develops internal hydraulic-pressure loss as the mechatronic unit ages. The 'bridge seal' adapter (the figure-8 sealing sleeve between the valve body/mechatronic and the transmission case) hardens and cracks, and the conductor plate/solenoids degrade, causing loss of line pressure. This is the single most common ZF 6HP fault and owners frequently misdiagnose it as a dead gearbox, replacing the whole unit when only the mechatronic seal or module is at fault. ATF that is never changed (Jaguar marketed it as fill-for-life) accelerates the failure. Well documented across the shared ZF 6HP platform (also used by BMW, Land Rover, Bentley, Maserati).
Common Symptoms
- Transmission fault / gearbox warning message (P R N D flashing)
- Transmission goes into limp / fail-safe mode
- Harsh or banging upshift
- Flared / slipping shift
- Delayed engagement from Park to Drive or Reverse
- Over-revving before the gear engages
How to Fix
Diagnose with live pressure/adaptation data before condemning the gearbox. In most cases the fix is replacing the mechatronic bridge-seal adapter plus the remaining sleeve/pin seals (sold as a kit) and a full fluid-and-filter (pan) service; more advanced cases need a remanufactured mechatronic/conductor plate. A complete transmission replacement is only warranted if internal clutches are burned.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine ZF 1068.298.090 mechatronic seal service kitOEMZF 1068.298.090
Confirmed internal mechatronic sleeve/bridge-adapter leakage during service of an XK ZF 6HP26 or 6HP28 Fitment/availability: ZF 1068.298.090 is explicitly the genuine seal kit for 6HP26/28/32 and includes sleeves/adapters. Confirm the tr…
- ZF 0501 216 243 / Jaguar C2C38963 integrated pan-and-filter kitOEMZF 0501 216 243 / C2C38963 / 1068.298.083
Pan-drop filter service on a tag-confirmed XK ZF 6HP26 or 6HP28 while addressing a proven mechatronic seal or fluid-service need Fitment/availability: The ZF pan/filter cross-references Jaguar C2C38963 and the live fitment includes XK 5.…
- ZF LifeguardFluid 6 one-liter bottleOEMZF S671.090.255 / C2C8432
Correct fluid for the tag-confirmed XK ZF 6HP26/6HP28 pan-drop/mechatronic service Fitment/availability: ZF S671.090.255 is LifeguardFluid 6 and cross-references Jaguar C2C8432. Sold per liter; determine quantity from the exact service s…
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Sources for this issue (3)
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 Jaguar?
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 Jaguar it is documented across 1 model: XK.
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 Jaguar?
Published repair estimates on Jaguar range from $900 to $3,000 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.