P0748 on Toyota: How to Diagnose & Fix
Pressure Control Solenoid "A" Electrical
2 Toyota models · 2 documented issues · 1 critical · $150-$3,800 repair
P0748 on Toyota by model: symptoms, diagnosis and fix
The XL10 Sienna used the Aisin U140E (FWD) / U140F (AWD) four-speed automatic. On high-mileage vans the valve body bores and shift solenoids wear, line pressure falls off, and the transaxle first flares between gears, then slips, then loses forward movement entirely. Shift solenoid E failure is a recognized failure mode across the whole U140 family (Camry, Avalon, Sienna). Toyota acknowledged the pattern with a service campaign covering a no-movement/slipping condition of the automatic transaxle. This is a first-generation transaxle - it is not the same unit or the same failure as the XL20 U151E torque-converter shudder or the later UA80E eight-speed.
Common Symptoms
- RPM flare between shifts
- Slipping under load or on hills
- Delayed or no engagement into Drive or Reverse
- Harsh 2-3 shift
- Check engine light with shift solenoid codes
How to Fix
Confirm with a line-pressure test and a scan for shift-solenoid codes before condemning the unit; a single failed solenoid or a worn valve body can sometimes be repaired far cheaper than a full rebuild. Sonnax and similar suppliers sell oversized valve/sleeve kits for the U140 pressure-regulator and lockup bores. Full failure requires rebuild or a used/reman transaxle. Toyota's extended-coverage campaign for the no-movement/slipping condition has long expired. Preventively, drain-and-fill Toyota T-IV every 30-40k miles - these units are unforgiving of burnt fluid.
Sources for this issue (3)
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)
P0748 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 P0748 mean on a Toyota?
P0748 stands for "Pressure Control Solenoid "A" Electrical." P0748 is a generic powertrain code meaning the transmission control module has detected an electrical fault — voltage or resistance out of the expected range — in the circuit for pressure control solenoid "A". This solenoid regulates hydraulic line pressure inside an automatic transmission, adjusting how firmly the clutches and bands apply based on speed, load, and throttle position. When the computer can't control the solenoid electrically, the transmission often defaults to maximum line pressure or limp mode, so you may feel harsh or erratic shifts, slipping, delayed engagement when shifting into Drive, or being locked into a single gear. Because it is an electrical-circuit code, the fault is usually in the solenoid itself or its wiring rather than a purely hydraulic problem, though contaminated fluid can damage the solenoid. Continuing to drive with slipping and overpressure shifts can overheat the transmission and lead to expensive internal damage, so this should be repaired promptly. On Toyota it is documented across 2 models: Sienna, 4Runner.
What are the most common causes of P0748?
The most common causes of P0748 are: Failed pressure control solenoid A (open or shorted solenoid windings), Damaged, frayed, or shorted wiring in the solenoid circuit, including the transmission case connector, Corroded or loose electrical connectors at the transmission harness, Low, dirty, or contaminated transmission fluid degrading or sticking the solenoid, Clogged transmission filter or debris in the valve body hydraulic passages, Faulty transmission control module or PCM driver circuit (rare). The specific cause varies by vehicle.
How much does it cost to fix P0748 on a Toyota?
Published repair estimates on Toyota range from $150 to $3,800 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 P0748 on a different make?
View P0748 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.